bureau of mineral resources, geology geophysicsnausori, fiji nadi, fiji 5. data reductions 6....

Bureau of Mineral Resources, Geology & Geophysics

BMR RECORD 1990/90

FIRST-ORDER REGIONAL MAGNETIC SURVEY OF SOUTHWEST PACIFIC ISLANDS,

JUNE-JULY 1989

by

A.P. Hitchman

B~\1R

Department of Primary Industries and Energy BUREAU OF MINERAL RESOURCES, GEOLOGY AND GEOPHYSICS

BMR RECORD 1990/90

FIRST-ORDER REGIONAL MAGNETIC SURVEY OF SOUTHWEST PACIFIC ISLANDS,

JUNE-JULY 1989

by

A.P. Hitchman

Geophysical Observatories and Mapping Branch

BMR

II ~ m UII II *R9009001*

~Commonwealth of Australia. 1990 This work is copyright. Apart from any fair dealing for the purposes of study, research, criticism or review, as permitted under the Copyright Act, no part may be reproduced by any process without written permission. Inquiries should be directed to the Principal Information Officer, Bureau of Mineral Resources, Geology and Geophysics, GPO Box 378, Canberra, ACT 2601.

SUMMARY

A first-order survey of eight magnetic stations in the southwest Pacific Ocean was conducted by the Bureau of Mineral Resources during June and July 1989. The purpose was to provide accurate information about the geomagnetic secular variation in the region to improve and extend the Australian Geomagnetic Reference Field, and for inclusion in global models of the field (notably IGRF) to improve their accuracy over the Australian region.

Stations were reoccupied at Noumea (New Caledonia), Port Vila (Vanuatu), Honiara and Santa Cruz Is (Solomon Islands), Tarawa (Kiribati), Funafuti (Tuvalu), and Nausori and Nadi (Fij i) . One old station in Suva (Fiji) used by the Carnegie Institution of Washington was also reoccupied, having been established by a British Naval survey party in 1896.

At each station a three-component fluxgate variometer and a proton precession total field magnetometer were used to measure field variations for about three days. A multichannel chart recorder was used to record continuously the four elements of the field, the temperature and time. Magnetographs were calibrated by frequent absolute determinations of the field. Sun observations were made to check the true azimuth of reference marks used for declination observations. Where possible, differences were measured between earlier and current stations to extend the time series.

The observed value of magnetic elements and preliminary mean hourly values for declination, horizontal intensity, vertical intensity and total intensity at the epoch of occupation are given. Station and reference mark descriptions are included, together with general information about each locality visited.

CONTENTS

Summary Page

1. Introduction 2. Preparation 3. Equipment 4. Station occupation reports

Noumea, New Caledonia Vila, Vanuatu Honiara, Solomon Islands Santa Cruz, Solomon Islands Tarawa, Kiribati Funafuti, Tuvalu Nausori, Fiji Nadi, Fiji

5. Data reductions 6. Conclusions 7. References

Appendices

1. Names and addresses of contacts 2. Pacific islands itinerary 3. List of hotels 4. Inventory of equipment

Tables

1 1 4 6 6 8

10 10 13 15 15 17 22 22 23

28 29 29 30

1. Stations established prior to 1985 31 2. Station coordinates and local meridian time 31 3. Variometer recording 32 4. Instrument comparisons and adopted corrections 32 5. Reference marks and azimuths 33 6. Observed field values 35 7. Preliminary mean hourly values 37 8. Adopted station values and secular variation at

epoch 1990.0 41 9. Secular variation derived from the IGRF85 model at

epoch 1990.0, and residuals 41 10. Station differences 42

Figures

1. Australian and Pacific first-order magnetic repeat stations operated by BMR. 2

2. Schematic diagram of first-order variometer equipment. 5

3. Noumea B & C: station descriptions. 7 4. Vila B & C: station descriptions. 9 5. Honiara B & C: station descriptions. 11 6. Santa Cruz A & B: station descriptions. 12 7. Tarawa B, C & D: station descriptions. 14 8. Funafuti C & D: station descriptions. 16 9. Nausori A & B: station description. 18

10. Suva Vou A: station description. 19 11. Nadi A & B: station descriptions. 20 12. Nadi C: station description. 21 13. Secular variation plots. 24

1. INTRODUCTION

The Bureau of Mineral Resources (BMR) measures and models the magnetic field of the earth in the Australian region. Permanent magnetic observatories provide the most accurate measures of the secular variation of the field, but are too few to give adequate spatial coverage in the Australian region. Repeat station surveys are carried out to determine the secular variation on a finer scale.

BMR repeat station survey work is carried out to first-order standards. This involves continuous recording of the vector field until two consecutive quiet night-time records are obtained. Absolute observations of the field are made at the repeat station itself throughout the day and are used to calibrate the variometer records. The data are subsequently corrected for the long term effects of magnetic storms using information from the nearest magnetic observatory. BMR repeat stations are reoccupied at approximately five-year intervals. Information is published as a numerical model of the geomagnetic field (the Australian Geomagnetic Reference Field), as five-yearly epoch charts of the seven components (elements) of the vector magnetic field and is sent to WDC-A, Colorado to be used in global models.

A number of agencies have been active in collecting magnetic field data in the Pacific at different times. During the early part of this century the Carnegie Institution of Washington (CIW) established magnetic stations on several Pacific islands as part of an effort to gather worldwide magnetic field data (Bauer, 1912; Bauer and Fleming, 1915; Bauer et a1, 1921; Fisk, 1927; Wallis and Green, 1947). During recent decades work has been carried out by the New Zealand Department of Scientific and Industrial Research (DSIR), the US Geological Survey, and BMR (Finlayson, 1971; Van der Linden, 1964). However, large parts of the region continue to have little or no history of magnetic data collection.

Until the 1985 first-order magnetic survey (Barton et a1, 1989) BMR work in the region had been restricted essentially to a small number of islands close to Australia. Relevant SW Pacific stations in existence before the 1985 BMR survey are listed in Table 1.

During the 1989 survey, observations were made at existing stations when possible. Auxiliary stations were installed at Honiara, Tarawa, Nausori and Nadi. Station differences between the primary and auxi1liary stations were measured. Figure 1 shows the present Australian network of first-order magnetic repeat stations. Coordinates of the Pacific stations are given in Table 2. Stations in Papua New Guinea are occupied routinely during the course of BMR first-order surveys (Hitchman & Bibot, 1987). The reoccupation of mainland stations is reported elsewhere (Hitchman, 1990; McEwin, 1984).

2. PREPARATION

Correspondence

In preparation for the survey letters were sent to appropriate authorities in each country, this included

the local geological/geophysical survey organization, giving background and aims of the survey; summary of previous collaboration; description of local station(s); requests for assistance, e.g. to be met at the airport, provision of an assistant during the survey.

the Civil Aviation authority, or Airport Manager, giving background and outline of the survey;

1

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MAGNETIC STATIONS IN THE AUSTRALIAN REGION

station description(s); request to reoccupy existing station(s); description of, and request for facilities for housing the variometers. customs authorities request for exemption from import duty on survey equipment.

and the Department of Foreign Affairs and Trade, Canberra, giving background and outline of the survey; copy of the itinerary;

- request to coordinate accomodation and vehicle hire arrangements through Australian diplomatic missions;

- copies of relevant correspondence with local geological/survey group, Civil Aviation and Customs authorities;

The list of contacts and addresses is contained in Appendix 1. In many cases replies were not received, but there was never any problem in securing permission and cooperation, provided full consideration was given to local regulations and requirements.

Weather

The weather in this region is quite changeable and varies significantly with location. Conditions during June - July 1989 were mostly hot and dry. As in 1985 Noumea was cloudy but dry, Port Vila was a little wet. Warm sunny conditions prevailed at all other locations, with the exception of occasional brief tropical showers.

Travel and transport

The itinerary for the work is set out in Appendix 2. Commercial flights operate to all destinations and were used throughout the survey. Early reservations are advisable to ensure uplift on the less frequently serviced sectors. All bookings were made through the BMR travel agent. Where possible vehicles were hired on location to cater for local travel. The necessary arrangements were made through the Australian diplomatic mission in the region. The availability of ground transport is variable.

In Noumea, Port Vila, Honiara, Fiji hire cars are readily available through major agencies.

On Santa Cruz Island there are very few vehicles. A local government vehicle was hired to move the equipment to and from the airport. Distances are such that operation on foot is possible though slow.

At Tarawa there was a car hire outlet although no vehicles were available due to (unusually) strong demand at the time. A taxi (with driver) was permanently hired for the visit. This proved an excellent arrangement.

At Funafuti there are no vehicles for hire. A government truck was used occasionally to move the equipment. Travel on foot is a viable means of transport.

The equipment was taken as excess accompanied baggage on flights. Certain of the destinations had only infrequent flights so it was important to ensure that the equipment always travelled with the geophysicist. As the aircraft were generally small the additional space requirement should be flagged when the ticket is booked. On some legs it was necessary to purchase extra passenger tickets to allow for the extra space. Onward arrangements should always be checked in person on arrival at each des tination. These arrangements are especially important for the Honiara-Santa Cruz-Honiara and Fiji-Tarawa-Funafuti-Fiji sectors.

3

Visas

Visas were required only for New Caledonia and Kiribati. This situation may change from year to year so these details should be confirmed before subsequent surveys. The BMR travel officer will be able to find out the requirement for visas at each destination.

Health

Malaria prophylactics are recommended for Vanuatu and the Solomon Islands.

Language

In New Caledonia it is advantageous to be able to speak French, particularly in dealing with the airport authorities. Scientists from ORSTOM (Noumea) will speak English reasonably well. At all other destinations English is widely spoken.

Accommodation

Accommodation was available at all locations. There are few hotels on Tarawa and only one at Funafuti so booking in advance is essential. A government resthouse operated at Santa Cruz Island and is the only facility of this type on the island. No meals are available at the resthouse but there is a kitchen in which they may be prepared. Some foodstuffs can be bought at small shops but provisioning is best done in Honiara. A twice-weekly market operates on the island at which local produce may be purchased very reasonably. At all other locations meals are readily available from the hotels. Appendix 3 lists the hotels used in 1989.

Customs clearance

Prior arrangements with customs authorities must be made to ensure that duty is not charged on the survey equipment. In preparation for the survey it was suggested that a caveat from the Chamber of Commerce would be useful. This option however proved far too expensive to be viable. The attention given the equipment varied enormously from country to country. It was very useful to have copies of the equipment inventory on hand. No customs duty was charged in any country.

3. EQUIPMENT

The equipment taken on the survey is listed in Appendix 4.

Variometer recording equipment

Variometers measuring four elements of the magnetic field were used throughout the fieldwork. A portable, three component EDA FM-lOOB fluxgate magnetometer was used to record continuously the variations of declination (D), horizontal intensity (H) and vertical intensity (Z) of the field. The total field (F) was monitored using an Elsec 595 proton precession magnetometer with a toroidal head which sampled the field at 1 minute intervals. A Doric Trendicator monitored the temperature of the EDA fluxgate sensors, using a Thermilinear YSI series 700 thermistor. These data were subsequently used to compensate for the temperature dependence of the sensors. Each of the four magnetometer channels and the temperature were recorded on a Tigraph six-channel analog chart recorder. A digital clock provided hourly pulses to the recorder to produce timemarks on the chart record. A diagram of the variometer system is given in Figure 2.

At each site the variometer system was housed in a convenient building with 240 volt AC power in the general vicinity of the repeat stations. It is

4

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I F

~

" EDA fluxgate ~ I EDA sens or

t H,D,Z

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BMR clock t

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240V AC

SCHEMATIC DIAGRAM OF FIRST ORDER VARIOMETER EQUIPMENT 24/03/10

Figure 2 Schematic diagram of first-order variometer equipment

5

important that the location be distant from any artificial magnetic activity (e.g. vehicles, power lines, radio transmitters) to allow variations in the earth's field to be recorded without disturbance. Table 3 gives details of the variometer recordings made at each station.

Absolute instruments

The recorded variations of the field were regularly calibrated throughout the station occupation. Absolute measurements of D, I and F were made for this purpose. From these three components any of the remaining four components of the field can be calculated.

The absolute instruments used throughout this survey were an Elsec declination-inclination magnetometer (DIM) and a Geometrics proton precession magnetometer (PPM). Each instrument was compared with standard instruments at the Canberra Magnetic Observatory before and after the fieldwork. Table 4 sets out the instrument differences measured during these comparisons, together with the preliminary corrections adopted for each instrument.

4. STATION OCCUPATION REPORTS

Sketches of station locations and reference marks are given in Figures 3 through 12 (in order of occupation). Station reference marks and their azimuths are listed in Table 5.

The names and addresses of contacts at each site are contained in Appendix 1.

At most stations small brass tubes set in cement pads were used to locate the feet of the tripod, and the centre of the station was marked with a "Commonwealth of Australia" brass plaque. The forced centre of the tripod defines the centre of each station (height 1. 22m above ground level). At stations where the forced centre of the tripod footpads does not coincide exactly with the centre of the plaque, the former is taken to be the centre of the station.

Cyclones are common in the southwest Pacific. Obj ects used for reference marks (e.g. buildings, masts, windsocks) can be damaged or completely removed. Care must therefore be taken to ensure that reference marks have not shifted.

NEW CALEDONIA

Noumea B,C Tontouta Airport (5-9 June 1989)

Contacts Contact was initially made with M. Jacques Recy, Chief Geophysics Department of ORSTOM in Noumea. Subsequent with M. Andre Lapouille of the same department. M. throughout the survey visit.

of the Geology and correspondence was Lapouille assisted

Permission to work on the airport at Tontouta was obtained from the Director of Civil Aviation, M. J. Bonizec. He directed the point of contact to the Airport Commandant, M. M. Pubellier.

The Director of the Customs service, M. R. Buffet, was advised of the intended visit.

Variometer installation After inspecting a number of sites on the airport the variometer equipment was eventually set up at the Tontoutel Hotel (room 50) about 1 km away. The same location was used successfully during the 1985 visit. Access to the

6

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ALL MEASUREMENTS IN METRES - NOT TO SCALE

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NOUMEA B,C TONTOUTA INTERNATIONAL AIRPORT

NEW CALEDONIA FIRST ORDER REGIONAL MAGNETIC STATION

LOCALITY AND REFERENCE MARKS

24/03/11

airport was closely monitored by the French army. The airport Commandant provided security passes for this purpose and no problems were encountered.

Azimuth Mark LHE Glide angle tower.

Observations Absolutes were made on both stations, using B as the main station. AM and PM sunshots were completed on station B, together with rounds of angles on Band C.

Equipment No problems were encountered with the equipment.

Station Upgrading No upgrading was carried out during the occupation. Both stations have 3 separate footpads and brass plaque and are easily located with the help of the station descriptions.

VANUATU

Vila B,C Bauerfield Airport, Efate Is (12-15 June 1989)

Contacts The Director, Department of Geology Mines and Rural Water Supply (Mr Colin Cheney, Acting), was the liason point during planning for the visit. An assistant from the same department, Mr Stanley Temokan, provided valuable help during the early stages.

Mr Mike Bergin, Acting Director of the Meteorology Department, laid the groundwork for use of the Met. facilities at the airport to house the variometer equipment.

Access to the airport was arranged through the Deputy Director of the Civil Aviation Division, Mr Chris Phelps, and the Airport Manager, Mr Joseph Kasten.

Variometer installation The variometers were set up in the technical workshop of the Met. installation at Bauerfield Airport. The same location was used during the 1985 survey. This proved a good site, convenient to the absolute stations and quiet, except for the hourly Met. radio transmissions. The sensors were placed beyond the west end of the building.

Azimuth Mark Top RHE of water tower at fire station.

Observations Station B was used as the primary station for absolute observations and sunshots (AM and PM). Rounds of angles were completed on both stations Band C.

Equipment No problems were experienced with any of the equipment.

Station Upgrading Both stations Band C were left as 3 separate footpads and brass plaque set in concrete.

8

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1

VILA B,C BAUERFIELD AIRPORT

VANUATU FIRST ORDER REGIONAL MAGNETIC STATION


24/03112

SOLOMON ISLANDS

Honiara B,C Henderson Airport, Guadalcanal (19-22 June 1989)

Contacts Initial enquiries regarding the proposed visit to the Solomons were directed to the Permanent Secretary of the Ministry of Natural Resources. Dr R. D. Walshaw, the Ministry's Principal Geologist (Economic), later took responsibility for arrangements for the visit. Throughout the occupation of the stations at Honiara Mr Bobby Kelly, an officer with the Seismology Section of MNR, assisted.

Introductory letters were also sent to the Comptroller of Customs and the Principal Aviation Officer to advise them of the visit and to seek the necessary clearances.

Variometer installation A tent supplied by the Solomon Islands Geological Survey was used to house the recording equipment during the occupation. The tent was located about 50 m beyond the end of the line of buildings to the west of the terminal at Henderson Airport. Power was taken from the Western Pacific office, the second to last building from the end. The end building, a hanger used by Pacific Helicopters, did not have permanent power connected and also took power from the Western Pacific office. The Pacific Helicopters operation at Honiara was in the process of being closed down during the 1989 visit. The location was an excellent one.

Reference Mark Main control tower aerial, centre base.

Observations Despite extensive searching station A, installed in 1969 by BMR, could not be located (station description in Barton et al (1989». Absolute observations were made on station B, as the primary station, and a newly installed secondary station (C). Sunshots (AM and PM) were made on B, rounds of angles were made on both stations, and an F survey was completed on station C.

Station Upgrading Station B was upgraded to a concrete triangle incorporating plaque and footpads. A new station (C) was installed with the same configuration.

Santa Cruz Is A,B Santa Cruz Is Airfield, Nendo Is (24-29 June 1989)

Contact As for the Honiara visit, initial enqu1r1es regarding the proposed visit to Santa Cruz Is were directed to the Permanent Secretary of the Ministry of Natural Resources. Again Dr R.D. Walshaw, the Ministries Principal Geologist (Economic), took subsequent responsibility for arrangements for the visit. Throughout the occupation of the stations at Santa Cruz Mr Bobby Kelly of MNR assisted.

Dr Walshaw made contact with the Permanent Secretary, Temotu Province to make the necessary arrangements for the visit.

Variometer installation The recording equipment was set up in a spare room in the Provincial resthouse at Lata. The sensor were placed to the west of the building. Little vehicular traffic comes to the resthouse which is reasonably remote from the maj or throughfares. The site was, however, disturbed by transmissions from the nearby Solomon Islands Broadcasting Commission repeater station. Interference was recorded on all traces for 3 hours

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HONIARA B.C HENDERSON AIRFIELD

SOLOMON ISLANDS FIRST ORDER REGIONAL MAGNETIC STATION

LOCALITY AND REFERENCE MARKS 24/03/14

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SANTA CRUZ ISLANDS FIRST ORDER REGIONAL MAGNETIC STATION


24/03/13

between 1800 and 2100 LT at night. Otherwise the site was magnetically quiet. The stations are about 2 km from the resthouse.

Azimuth Mark Windsock to the west, centre at level of horizon.

Observations Absolutes were made on both stations A and B, using A as the primary station. Sunshots (AM and PM) were completed on A together with rounds of angles on A and B.

Equipment No problems were experienced with the equipment.

Station Upgrading Both stations are set in coral and did not require concreting. footpad was however concreted into station A.

A third

REPUBLIC OF KIRIBATI

Tarawa B,C,D Bonriki Airfield (1-6 July 1989)

Contacts Mr Peter King, the Land Surveyor with the Lands and Surveys Division, Ministry of Home Affairs and Decentralization, assisted with the preparations for the visit to Tarawa. He arranged for the the stations to be located at the airport before the survey commenced. He also 1iased with Cus toms regarding the entry of the equipment into Kiribati, and made prior arrangements for a security pass to allow free access to the airport.

Early contact was also made with Mr Rubi Tenano, Officer, Ministry of Transport and Communications, planned survey work on the airport,

Variometer installation

the Principal Aviation to inform him of the

As in 1985, the recording equipment was set up at pump station no. 1 at the Bonriki water reserve. The recorders were operated in the attendant's office with the sensors kept within the station fence to the south of the office. The station's low-power radio transmitter caused minor interference during the daily communications.

Azimuth Mark Centre base of LH aerial on control tower.

Equipment No problems with the equipment were experienced.

Observations Absolute observations were made on stations B, C, and D, using B as the primary station. AM and PM sunshots were made on station B, and rounds of angles on all three stations. An F survey was carried out at the site of the new station D.

Station Upgrading Stations Band C were in existence before the 1989 visit and comprised a concrete triangle incorporating the footpads and plaque. They are in danger of being disturbed if the proposed upgrading of the airport eventuates. A site which should be largely unaffected by any construction work was chosen and a new station (D) installed. The station is a concrete triangle enclosing a brass plaque and three footpads.

13

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TARAWA B, C, DBONRIKI AIRFIELD

KIRIBATIFIRST ORDER

REGIONAL MAGNETIC STATIONLOCALITY AND REFERENCE MARKS

24/03/16

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TUVALU

Funafuti C,D Funafuti Airport (7-9 July 1989)

Contacts The Secretary, Ministry of Commerce and Natural Resources was the initial point of contact for the visit. Mr Kelese Kolone was acting in this position during the survey. He granted access to the stations on the airstrip and helped with transport needs. Mr Siniala Auenga, the government Lands Officer provided valuable assistance during the visit.

Variometer installation The variometer equipment was set up in a house behind the Tuvalu Broadcasting Service and close to the airport terminal. The house belonged to the government and was provided as accomodation during the visit. Although being right in the residential part of Funafuti there was only minimal vehicular traffic and very little other magnetic disturbance to the records. The house was about 500 metres from the stations.

During the 1985 visit the variometers were set up in a house quite close to the stations and well removed from almost all magnetic interference. The house is directly opposite the stations and is the last in the line of houses at the lagoon's edge. It is privately occupied and a request to use it is probably best directed through the Secretary of the Ministry of Commerce and Natural Resources.

Reference Mark Spike atop LH radio mast to the NW

Observations Absolute observations and rounds of angles were made on both stations using C as the primary and D as the secondary station. AM and PM sunshots were made on station C.

Station Upgrading Both stations have three footpads and a brass plaque set in a concrete triangle.

FIJI

Nausori A,B Nausori Airport (12-15 July 1989)

Contacts As for the 1985 visit to Fiji, the Principal Surveyor, Department of Lands and Survey, was contacted to begin arrangements for the visit. During the occupation of the stations in the vicinity of Suva Mr Paserio Samisoni, a surveyor with the same department, provided valuable assistance.

Mr Joseph Kamali, the airport manager arranged the issue of security passes and the use of the Telecom communications hut for the variometer installation.

The Customs authorities in Suva were also advised of the visit.

Variometer installation The equipment was set up in the radio communications hut used by Telecom to house receiver equipment. The hut is located to the north of the main runway and is accessed from Kuku Road. This was an excellent site for the recording equipment.

15

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FUNAFUTI C, 0 FUNAFUTI AIRPORT

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FIRST ORDER REGIONAL MAGNETIC STATION LOCALITY AND REFERENCE MARKS

24;03/17

Reference Mark TDC of aerial by Air Pacific hangar.

Observations Absolute observations were made on stations A,B and Suva Vou A, using Nausori A as the primary station. Rounds of angles were also made on all stations. The 1986 azimuth data obtained by the Fiji Department of Lands and Surveys was again used in the calculation of the 'D' observations.

Station Upgrading A new station (B) was installed at Nausori airport on the grassed unused runway 484m from station A. B has a brass plaque and footpads enclosed in a concrete triangle at ground level.

Nadi A,C Nadi International Airport (17-20 July 1989)

Contacts The Principal Surveyor of the Department of Lands and Surveys was the initial point of contact for the occupation of the Nadi stations.

Authority to work within the airport precincts was obtained from the airport manager, Mr Bill Waka. He subsequently directed the point of contact to the following people,

· Mr Joe Savu, the Airport Development Officer, for assistance with the location of the stations,

· Mr Jone Tuliatu, Chief of Air Traffic Services, to obtain clearance to work in the operational areas of the airport, and

· Mr Nasir Khan, A/Chief of Telecommunications Services, for permission to use the airport receiver building to house the recorders. In Mr Khans absence, Mr Momo Seeto, the Station Officer (Telecommunications), made the building available for this use.

Variometer installation The recording equipment was set up in the Telecommunications receiver building within the airport grounds. This was the location used in 1985 and again proved to be a suitably quiet site. This building is accessed via the airport perimeter road. The equipment was set up in the kitchen area of the building with the sensors in long grass to the east. A key was provided by Mr Momo Seeto for the duration of the visit.

Azimuth marks LH peaked dome on moslem mosque TDC control tower light

Observations

(station A) (station C)

Absolute observations, rounds of angles and and C, using A as the primary station. observations were made on B. A PPM site station C.

Equipment

sunshots were made on stations A Due to its closeness to A, no survey was also carried out on

The Elsec 820 PPM variometer became a little unreliable during the occupation. It would stop functioning without provocation and occasionally resume operation after being idle for a number of hours. It was replaced with a spare unit.

Station upgrading Footpads previously hammered in the ground at station A were concreted to make them more permanent. A new station (C) was installed in the vicinity of the receiver building. It has three footpads and a brass plaque set in a concrete triangle at ground level.

17

1.0'60°

n OUT010 143

0 Radio communications field hut

STN

Foncr Gateof main

Erg

Culvert

Fence13

4 STN A

\i 9°

-4J.

DME post

I Near radion

0 0 Tank

DME -buiding

c,

— — _36.8 I

33 7

ALL MEASUREMENTS IN METRES — NOT TO SCALE

NAUSORI A, BNAUSORI AIRPORT

FIJIFIRST ORDER REGIONAL MAGNETIC STATION

LOCALITY AND REFERENCE MARKS24/03/18

Cementculvert

2

73'

-

33

I"J;I 1-"

OQ ~ 11 CD

~ 0

C/.I

~ III

<: 0 s:: ;J>

til rt III rt 1-" 0 ::l p.. CD til n 11

~ 1-" \,0 "0

rt 1-" 0 ::l

Laml town

Blue house

OJ

Cliff - 5m-...

SUVA HARBOUR

To Suva Vou village

Cemetery

Cleared grouno. stumps and low hushes

SUVA HARBOUR ~


~ N

I Lat 18 0 07 '06"S Long 178°25'00"E

TDC black and red beacon

RH storage tank

TDC black and white beacon

TDC red and white beacon

Dark pole with platform on top

l

!

SUVAVOU A CUFFY POINT

FIJI FIRST ORDER REGIONAL MAGNETIC STATION

LOCALITY AND REFERENCE MARKS 24/03119

t-:rj 1-'-

()Q ~ Ii CD

t-' t-'

Z P> p.. 1-"

~

R'> t;d

rn rt P> rt 1-'-0 ::s p.. CD rn (")

Ii I'V 1-'-0 "C!

rt 1-'-0 ::s rn

/

Anemometer mast

STN C... #BllllctHlg ractlo receiver station

• Control tower

I t1J

/

STN B (concrete block)


White

TOC LH receiver

mast

m

Inscription

~ N

I

STN B

Theodore lig ht

Trig station 2

Mosque LH minaret

LH peaked dome on mosque

NADI A, B NADI AIRPORT


LOCALITY AND REFERENCE MARKS 24{03/21

t:I:j 1-"

(JQ ~ Ii !tl

t-"

'" Z III Po 1-"

(")

en rt III rt 1-" 0 ::s Po ('D en (')

Ii 1-"

"d rt 1-"

N 0 I-' ::s

en

I

I I

I

/

I I

/

I

/

/ I

I

r-~

/ I

/ /

,--/ /00

I 0

00 Cement n 0 blocks

Gentle slope down -2m

STN C A ;SlIIldlnq mdlo receiver' .st{1tICHl

tV

/

AA

Perimeter road

to runway

.. STN A ~mlnal

4 .. .. • Control towp.r

Houses - - - - - - - - Fence

Receiver hUlldlllg


1 N

I

Trig station 2

NADI C NADI AIRPORT



5. DATA REDUCTIONS

Absolute observations were used on-site to calibrate the magnetograms. Scale values (in nT/mm or min/mm) were determined for each magnetic field trace by graphing the observed value and the distance from a baseline, scaled from the magnetogram. From this data preliminary baseline values were derived:

Baseline = Field value - (scale value * scaling)

The consistency of the baseline values reflects the quality of the data being recorded, and was used to monitor the adequacy of the occupation before the station was closed.

On returning to BMR, the instrumental absolute observations were recalculated and preliminary instrument corrections (Table 4) applied to give the observed field values in Table 6. The magnetograms were digitized at hourly intervals, the calculations reworked and temperature and preliminary instrument corrections applied to produce revised baselines and scale values for each trace. Preliminary mean hourly values were then derived from the digitized data combined with the magnetogram parameters. These are contained in Table 7.

The data reduction was checked by plotting the values of the magnetic elements, derived from the absolute observations, onto the MHV plots.

The aim of each occupation of a first-order magnetic station is to describe as accurately as possible the long term quiet field at the station. Since the magnetic field is subject to activity of varying intensity which is superimposed on the quiet daily variation, some way of accounting for the 'non-quiet' magnetic activity must be found. The effect of short term disturbances is reduced by continuing the occupation until at least two magnetically quiet nights are recorded. It is the field around local midnight on a magnetically quiet night which most closely represents the value of the long-term quiet field (McEwin 1984). To remove any continuing long term disturbance such as magnetic storms (which can depress H for weeks afterwards), a more representative mean value of the quiet field at a station is obtained by comparing the morphology of variations recorded at the station with several months of variations recorded at a suitably close magnetic observatory. This is possible since the form of variations of the magnetic field generally does not seem to change significantly over small distances (say 1000 km) at similar latitudes.

The final stage of the data reduction is to adopt a station value for each of the seven magnetic elements. This value is the best estimate possible for the long term quiet field at the station. Table 8 sets out the adopted values of the magnetic elements for epoch 1990.0. Figure 13 shows the secular variation for each station. Annual changes derived from the IGRF85 model at epoch 1990.0 are given in Table 9, together with residuals obtained by subtracting the IGRF values from the first-order values.

Differences between the main and the supplementary station at each location are listed in Table 10.

6. CONCLUSIONS

Except for the offset of about 5 nT in the total field secular variation over the region, no systematic differences are observed in the residuals. This indicates that the IGRF85 model of the field is a fair approximation to the actual field in this region. Attention is drawn to the relatively large annual changes measured in the Declination at Nausori and Tarawa. These are obtained from only two occupations of each station (in 1985 and 1989).

22

Subsequent visits will clarify these results. It will be noted that the annual change in the easterly component of the field is likewise relatively large, having been calculated using the Declination results.

7 . REFERENCES

Barton, C.E., A.P. Hitchman, A.J. McEwin, 1989, First-order regional magnetic survey of southwest Pacific islands, May-July 1985. Bureau of Mineral Resources Report, 289.

Bauer, L.A., 1912, Land Magnetic Observations, 1905-1910. Researches of the Department of Terrestrial Magnetism, Carnegie Institution of Washington, Vol 1.

Bauer, L.A., J.A. Fleming, 1915, Land Magnetic Observations, 1911-1913 and Reports on Special Researches. Researches of the Department of Terrestrial Magnetism, Carnegie Institution of Washington, Vol II.

Bauer, L.A., J.A. Fleming, H.W. Fisk, W.J. Peters, 1921, Land Magnetic Observations, 1914-1920 and Special Reports. Researches of the Department of Terrestrial Magnetism, Carnegie Institution of Washington, Vol IV.

Finlayson, D.M., 1971, First Order Magnetic Survey of the Territory of Papua and New Guinea, 1969. Bureau of Mineral Resources Record, 1971/26

Fisk, H.W., 1927, Land Magnetic and Electric Observations, 1918-1926. Researches of the Department of Terrestrial Magnetism, Carnegie Institution of Washington, Vol VI.

Hitchman, A. P., L. P. Bibot, 1987, First-order regional magnetic survey of Papua New Guinea, March - April 1985. Bureau of Mineral Resources Record, 1987/1

Hitchman, A.P., 1990, First-order regional magnetic survey of Australia, for Epoch 1990.0, 1986 - 1989. Bureau of Mineral Resources Report, 301.

McEwin, A.J., 1984, First Order Magnetic Survey of Australia for Epoch 1980.0, March 1978 July 1979, Operations Report. Bureau of Mineral Resources Record, 1984/15.

Van der Linden, J., 1964, Regional Magnetic Stations on some Islands in the Pacific and Indian Oceans, 1957 and 1959. Bureau of Mineral Resources Record, 1964/47

Wallis, W.F., J.W. Green, 1947, Land and Ocean Magnetic Observations, 1927-1944. Researches of the Department of Terrestrial Magnetism, Carnegie Institution of Washington, Vol VIII.

23

•

A

..... .........^.....^......

14.0

13.0

12.0

11.0

1990

31.400

3l.201)

34.000

33.900

1990

Funafuti

A

A12.0

11.0

10. 0

9.0

P cc"=0

35.600

35.400

35.200

35.000

34.800

34.600

8 - 0^.1111^i^11^ 34.400 1 1'1'1'1^1^1^1.19 0^1930^1950^1970^1990

1920^1940^1960^1980Year

19 0^1930^1950^1970^19901920^1940^1960^1980

Year

41.42%.5s1

0.c

38.000

37.800

37.600

37.400

37.200

37.000 .1.1.1.1^1^ii19 0^1930^1950^1970^1990

1920^1940^1960^1980Year

Honiara

10.0

a10 ^

A

&O .̂

1950^1320 19a0^1193

Yam^ Ter^ Yea.

Nadi

Figure 13 Secular variation plots.

24

0'

'" " o

Funafuti

12.0.---------------------, 35.600 r--:-A--------------~

...... c 35.100 ---~---.-----------------------------------------.-.--._-

35. 200 --------.-----------------------------------------------'---'"

10.0 ---------------------------------.-.--.-.. --.--.---------------. 35. 000 ------------------------------------------------.--------------..

9.0 ---~--------------------------------------------------31. 800 ----------------------------------------------------------------

;.. 31. 600 ------------------------------------------------------------~

B.O~r_~~_,_._._r_r_r_."._,_~

1910 1930 1950 1970 1990 1910 1930 1950 1970 1990 1920 1910 1960 19BO 1920 1910 1960 1980

Year

38.000 .-------------------~

.. 37. 800 -------~-----------------------------------------------

<A ~ -g 37. 600 ------------------------------------------------------------1- .. cIA ~:J

... 2 37.100 ----------------------------------------"-----------t-

37. 200 ---------------------------------------------------------~

37.000 f--..-..-..-..-..-..-..-..-..-..-..-..-..-..-I...-I 1910 1930 1950 1970 1990

1920 1910 1960 19BO Y .. ar

Honiara

Y .. ar

11.0,-----------, ~OOOr-----------------~ 11.500..-----------.

lao ------------------.-.--.. --.----.. ---.. A

lillll ------------ -------------------------- 11.100 ------------------------------------.

!l.0 ------•. ---A

It.Ill --------------------------.------.... 8.0 ------------------.-------------.-----.

1.01f----.---.--r-.----,---,----, li 100 f--.....,.--,.--..---.---.--- 11.100 1---.---.--_.----,---,--

IfI6lI IS}\) 1!Bl IE 19t.Q ISIIl 1!Bl IE IfI6lI 1!Bl IB

I ...

Nadi

H.O,----------------- 31.1()(),-----------------, 11.200.-------------

A

A 31.200 -------.-- .. -----.--- .. -.--.-----.-----.---.--.--13.0 -------------------------------------------.- ... -

H.OOO -----

13. BOO ----------------- ----.------- .. -.. --... -.-.--.--

'13.600 ------------------------------ .. -.--.---.----- .. A

11.0 ----------------------------------------------- 33.800 ------------------------------------ -----------13.100 ------------.----------------............. ..

1~0r_-._.--,__.--~_.--r_- 33. 600 I---_,_-.---r-....--,-..--,r-~ 13.~.~_,_-._~-.___r--_._~~

1950 1960 1970 1980 1990 1950 1960 1970 1980 1990 1950 1960 1910 1980 1990

Y.ar

Figure 13 Secular variation plots.

24

Nousori 13.5r---------------------------------------~ 33500r-------------------------------------~

13.~ A 33400

.~ 134 33300 A

33200

n.? 33100

13.1 +------,-----,-----..,......-----1 33000+-----r----~---~---~ 1980

o Go II

o

1990 2000 1980 Year

43500r----------------------------,

43400

..•......... ~. A

43300

43200

43100

1990 YOOf

43000~---~----~-----~-----~ 1980 2000

Noumea

1990 YfI<JI

;'000

1~.0r------------------------------------, 33.600r--A--------------------------------.

13. 0 I-------------I? B

::: ::: -~----~-----------~--~---~--~--~~~~~~=~-.------.~ 33. 000 --==~~-- --- ------

12.0 -----.-.. --- - -.- ------. -- --.. -.. -.- -----------. -32.800

32.600 II. 0 I--~----------------- --.-------

32.~00 B

- -- -"'" 10.0~~~_r_r_r..,......~._~,,~_r_r_r~

1900 1920 19~0 1960 1980 1910 1930 1950 1970 1990

Y&oar

1900 1920 19~0 1960 19BO 191 0 1930 I 950 I 970 I 990

YeC:lr

i9.200r----------------------------------.

A

49. 000 -~----- .. --------.. -.--

48.800 --.-.. --.-.-.. -.------------.--.. --.--.-... ---

1S. 600 1------------------------.-.----

\ ~100 T I I I

1900 1920 1940 1960 1980 1910 1930 1950 1970 1990

V..,ar

Figure 13 Secular variation plots (con't)

25

C>

'" u v

o

Port Vila

12.0~------------------------------•. ~ -8

11. a 1---.----.--.--.------.. -------.... - ..

10.0 1-----.---.-----.-----.-------

~ A

9.0~-----------------------------

S.O I I -1 1910 1930 1950 1970 1990

1920 1910 1960 19BO Year

35.000~A~----------------------------~

3 .... BOO .~.------.----,--.-------------

31.600 ---- ----_._ .. _--_._-_._-_._-_._---_._-_.

3 ....... 00 .. _-----_ ... _ .. _-_ ... _. _._. __ .. - _.--- --_._---

31.200 --------_._--_ .. _--_._---

31. 000 -------.---.--.. -.. ---.---.- .----

33. sao -----.---.-.. -.---.. -----.. - ... -----~.-

33.600~~~~'-'--r-r-r-T~-'~--r-r-~ 1910 1930 1950 1970 1990

1920 1910 1960 19BO Yfi?ar

"I5.S00~---------------------------'

"IS. 700 ~--c-,.4-----

A

"15.600 --------_._--------

"15.500 ----!?-

15."100 1--------

15.300~r_r_r_r_r_r_._._._._._._~,_,_~

1910 1930 1920 1910

1950 1970 1990 1960 19BO

Y€"ar

Santa Cr uz Island

1~.:: I-----------------~ 35500r------------------------------~

10.4 35400

;:: 1 ~.3 35300

A I

35200

10.1 35100

10.0 :',::-----r-----..------r------1 1980 1990

Year 2000

35000_+-------~---------r--------~------~ 1980 1990

Yoor 2000

Figure 13

41500r-----------------------------------~

41400

41300

41200

41100

4100?9~8~0------------------19~9-0---------r--------?~QOO Year

Secular variation plots (con't)

26

'" .. "0 v

a

Tarawa

12or_------------------------------, 35.100r---------------------------------,

11.0\--------------------------··--

10.01--------------------- - --------------------

.. A

35.2001---------------------------------

35.000 ----------------------------

9.01--.---------------------

31.800 ----------------------------

31.600 ------------------------------------ ---~ A

B.O~~,,_.~-._y_r-r-r-r_r~-r~~ 3~.100~r_r-r_._~._._._.-._T-._~._~

1910 1930 1950 1970 1990 1920 1910 1960 1980 1910 1930 1950 1970 1990

Ye .. r 1920 1910 1960 19BO

35.100r-... -------------------------------, A

35.200 ---------------------------

35.000----------------------------

31.800 ----------------------------

31. 600 ~---------------------------

31.100r-~,_,-,_-r_r-r~~_,~r-r_r-~,_,

1910 1930 1950 1970 1990 1920 19~0 1960 1980

y", .. r

y .... r

Figure 13 Secular variation plots (con't)

27

APPENDIX 1 Names and addresses of contacts

Australia

The Director South Pacific Regional Section South Pacific, Africa, Middle East

and South Asia (SAMS) Division Department of Foreign Affairs and

Trade Administration Building Parkes ACT 2600

Fiji

The Principal Surveyor Control Department of Lands and Survey PO Box 2222 Suva Fij i

The Director of Mineral Development

Ministry of Energy and Mineral Resources

Suva Fiji

The Manager Civil Aviation Authority of Fiji Private Bag Nadi International Airport Nadi Fij i

The Airport Manager Civil Aviation Authority of Fiji Nadi International Airport Nadi Fiji

The Airport Manager Civil Aviation Authority of Fiji Nausori Airport Nausori Fiji

New Caledonia

The Chief Scientist Dept of Geology and Geophysics ORSTOM BP AS Noumea-Cedex New Caledonia

28

M. le Directeur Direction Generale de l'Aviation Civile BP Hl Noumea-Cedex Nouvelle Caledonie

M. Ie Directeur Service des Douanes Noumea-Cedex Nouvelle Caledonie

Republic of Kiribati

The Chief Lands Officer Ministry of Home Affairs and Decentralization Lands and Surveys Division Box 7 Bairiki Tarawa Republic of Kiribati Central Pacific

The Director Division of Civil Aviation Betio Tarawa Republic of Kiribati Central Pacific

Solomon Islands

The Chief Geologist Solomon Islands Geological Survey Ministry of Natural Resources PO Box G24 Honiara Solomon Islands

The Principal Aviation Officer Civil Aviation Division Ministry of Posts and Communicatio GPO Box G2S Honiara Solomon Islands

The Comptroller of Customs Customs and Excise Division PO Box 201 Honiara Solomon Islands

Tuvalu

The Secretary Ministry of Commerce and Natural Resources Vaiaku Funafuti Island Tuvalu

The Secretary Ministry of Works and Communications Vaiaku Funafuti Island Tuvalu

The Secretary to the Government Office of the Prime Minister Vaiaku Funafuti Island Tuvalu

APPENDIX 2 Pacific islands itinerary

DATE FROM TO DEP

4/6/89 Canberra Sydney 1125 4/6 Sydney Noumea 1345

10/6 Noumea Pt Vila 2255 17/6 Pt Vila Honiara 0630 24/6 Honiara Santa Cruz 0700 28/6 Santa Cruz Honiara 1100 29/6 Honiara Nadi 1810 1/7 Nadi Tarawa 0700 7/7 Tarawa Funafuti 0815

12/7 Funafuti Suva 1200 22/7 Nadi Melbourne 0900 22/7 Melbourne Canberra 1525

APPENDIX 3 List of hotels

New Caledonia

The Director of Customs Customs and Excise Department Vaiaku Funafuti Island Tuvalu

Republic of Vanuatu

The Director Geology Mines and Rural Water Supply Private Mail Bag Port Vila Republic of Vanuatu

The Director Civil Aviation Department Port Vila Republic of Vanuatu

The Airport Manager Bauerfield Airport Port Vila Republic of Vanuatu

ARR CARRIER

1210 Ansett 1725 Qantas 2255 Air Caledonie 0835 Air Niugini 1015 Solomon Airlines 1430 Solomon Airlines 2210 Air Pacific 1430 Air Marshall 1200 Air Marshall 1545 Fij i Air 1225 Qantas 1620 Australian

FLIGHT

AN356 QF09l SB238 PX085 IE853 IE854 FJ505 CW002 CW001 PC601 QF018 TN039

Tontoutel Hotel, B.P. 93, Tontouta, tel: 351111. Excellent, pool, about 1 - 2 km from Tontouta Airport, 38 km from Noumea; moderately expensive.

Vanuatu Olympic Hotel, PO Box 709, Port Vila. Tel:2464. Pleasant, moderately priced, located in the middle of town overlooking the harbour, about 5 km from the airport, parking facilities are poor and remote from many rooms.

Solomon Islands Hotel Mendana, PO Box 384, Mendana Avenue, Honiara. This is the main hotel in Honiara, excellent; international standards; walking distance from shops, restaurants and Australian Embassey; ocean

29

frontage, approximately 12 km from Henderson airport.

Government resthouse, Santa Cruz Island, Lata. Inexpensive, basic accomodation, self-catering only, about 3 km from airport, advance reservation essential.

Republic of Kiribati Otintaai, Bikenibeu, Tarawa. The only international class hotel on Tarawa, about 7 km from Bonriki Airfield. Recommended. Kiribati Hotel, Betio, Tarawa. Basic accomodation, on atoll most remote from the airport.

Tuvalu Vaiaku Lagi Hotel, Vaiaku, Funafuti. VLH.

Tel: 733 & 744 Telex: TU4800 Cable

Only hotel on Funafuti atoll so advance reservation is essential. Government operated, very pleasant, beautiful location, get a room remote from the bar to avoid disturbance, 200 m from the airfield, good catering.

Fiji Travelodge, Suva. Good quality hotel, moderately expensive, pool, good catering, walking distance to town and Government offices.

Castaway Gateway Hotel, Nadi. Tel: 72444 Top class; reasonably priced, caters for tourist trade, very convenient for airport, parking is not adjacent to rooms.

APPENDIX 4 Equipment inventory

1. Recording Box 1

Tigraph chart recorder

EDA sensor

EDA/Doric cable

spikes (short, long, collar)

circuit breaker

tape measure

tent fly

8 tent pegs

6-piece aluminium poles

spare Tigraph paper (1 roll)

2. Recording Box 2

Elsec 820 consoles (2)

Elsec power supply

Elsec sensor and cable

3 pc pole, 3 pegs, twine, adaptor

EDA console + lead

Doric thermograph + lead

Digital clock

power distribution board

toolkit & toolroll

Fluke multimeter

jewellers screwdrivers

torch

spare fuses

nuts + bolts

extension lead

3. Esky 4. Absolute Box

QHM circle 14

QHM 173

tent pegs (3)

aluminium pole (1 pc)

hammer

compass

electrical tape

hacksaw

soldering iron and Flux

station markers (10)

brass footpads (21)

nylon rope

masking tape

block of wood

spare aluminium catches

analog stopwatch

damping magnets

EDA cards

batteries

tent fly

QHM thermometer

electronics cleaner

garbage bags

BNC - banana plug connectors

forms

station descriptions

tent repair kit

raincoat

30

Zeiss theodolite 317214

DIM console 208

Geometries G816/1024 + sensor

Geometries G816/1025 + sensor

digital stopwatchs (2)

radio

calculators + handbooks

observing fly

8 tent pegs

stand for ppm sensor

absolute forms

pencilling boards (2)

5. Tripod Bag

theodolite tripod

Askania tripod

poles for observing shelter

umbrella

3 lengths aluminium

Table 1 Stations established prior to 1985

Station Year Organization

Funafuti A 1915 CIW B 1915 CIW

Honiara A 1981 BMR Nadi A 1952 NZ DSIR

B 1952 NZ DSIR Nauru A 1937 CIW

B 1974 BMR C 1981 BMR

Noumea A (town) 1915 CIW Suva Base Station 1906 CIW Suva Vou A 1906 CIW Tarawa A 1915 CIW Vila A 1981 NZ DSIR

Table 2 Station coordinates and local meridian time

Station Latitude Longitude Altitude Local Meridian Time d m s d m s m hr:min:sec (UT)

Fij i Nadi A -17 45 16 177 27 11 3* 00:10:12

B -17 45 16 177 27 11 * 3* Nausori A -18 02 01 178 33 47 10* 00:05:45

B -18 02 01 178 33 47 * 10* Suva Vou A -18 07 06 178 25 00 5* 00:06:20

Kiribati Tarawa B 01 22 45 173 08 38 2* 00:27:25

C 01 22 41 173 09 11 2* 00:27:23 D 01 22 41 173 09 11* 2*

New Caledonia Noumea B -22 00 35 166 11 58 8.5 00:55:12

C -22 00 39 166 11 52 11 00:55:12

Santa Cruz Island Santa Cruz Is A -10 42 48 165 47 34 2* 00:56:50

B -10 42 44 165 47 43 2* 00:56:49

Solomon Islands Honiara B -09 25 25 160 02 48 * 10 01:19:49

C -09 25 25 160 02 48 * 10

Tuvalu Funafuti C -08 31 53 179 11 58 1* 00:03:12

D -08 31 56 179 11 55 1* 00:03:12

Vanuatu Pt Vila B -17 41 54 168 18 12 00:46:47

C -17 41 55 168 18 11 00:46:47

Note. * these values are uncertain.

31

Table 3 Variometer recording

Station Start End Remarks

Funafuti 0354 07/7/89 1948 10/7/89 good record (H,D,Z,F,T) Honiara 0000 20/6/89 2210 22/6/89 good record (H,D,Z,F,T) Nadi 0407 17/7/89 0125 20/7/89 good record (H,D,Z,F,T)

lost 4 hrs F trace Nausori 0414 13/7/89 2103 15/7/89 good record (H,D,Z,F,T)

lost 10 hrs F trace Noumea 0412 05/6/89 0024 09/6/89 good record (H,D,Z,F,T) Santa Cruz Is 0525 24/6/89 2246 26/6/89 good record (H,D,Z,F,T)

3 hrs radio int., all traces

Tarawa 0020 03/7/89 2337 05/7/89 good record (H,D,Z,F,T) some vehicular and radio interference

Vila 0016 12/6/89 2248 15/6/89 good record (H,D,Z,F,T) traces affected by Met. radio

Table 4 Instrument comparisons and adopted corrections

Station Date Instrument A Instrument

Declination Inclination Magnetometer Canberra 5/4/89 Ruska 4813 312714/208

QHM 461/MNS2.3 312714/208 7/8/89 Ruska 4813 312714/208

QHM 461/MNS2.3 312714/208

Proton Precession Magnetometer Canberra 5/4/89 MNS2.3 E770/193

2/6/89 MNS2.3 G816/1024 7/8/89 MNS2.3 G816/1024

MNS2.3 G816/1025 11/9/89 MNS2.3 E770/193

Adopted corrections

Ds DIM 312714/208 - 0.4/ Is DIM 312714/208 + 0.0/ Fs E1sec 770/193 - 0.6 nT Fs = G816/1024 + 0.9 nT Fs = G816/1025 - 3.6 nT

32

B A-B

'D' 0.1/ / I / 0.2/ 'D' -0.2/ / I / 0.3/

-0.5nT 1.7nT O.OnT

-3.6nT -O.SnT

Table 5 Reference marks and azimuths

FIJI Nadi A

Trig #1 on hill Trig #2 on hill LH minaret of mosque LH peaked dome on mosque TDC control tower light TDC LH receiver mast Station B

Nadi C Trig #1 on hill Trig #2 on hill LH minaret of mosque TDC control tower light

Nausori A Pill box, RHE Station B Air Pacific radio mast, TDC RH red antenna mast, TDC RH member

Nausori B Pill box, RHE Air Pacific radio mast mast, TDC RH red antenna mast, TDC RH member Station A

Suva Vou A Red & black beacon Black & white beacon Red & white beacon Grey pillar with platform

13 09 58 45 15 30

147 45 33 RM 147 58 15 89

188 08 19 306 12 42 315 15 03

23 53 55 52 09 42

131 10 36 RM 142 07 47 89

145 49 22 173 33 33

* RM 176 41 33 86 193 54 39

19 14 38 RM 179 37 44

209 41 52 353 33 33

209 51 29 * RM 210 55 58 86

219 55 14 220 06 25

* Azimuths from Fiji Dept of Lands & Survey, Sept 1986.

KIRIBATI Tarawa B

Centre base of left antenna on control tower RM Centre base of inverted 'L' antenna on control tower Station C Station D East Windsock, centre base

Tarawa C Station D Station B Centre base inverted 'L' antenna on control towerRM Cement post, RHE base

Tarawa D

91 42 00 92 04 06 96 52 23

100 21 18 101 37 59

138 08 02 276 52 23 280 15 10 307 08 09

Station B 280 21 18 Centre base inverted 'L' antenna on control towerRM 285 28 14 Station C 318 08 02

NEW CALEDONIA Noumea B

89

Glide angle tower, LHE Transmitter antenna, LHE (largest of group) LH receiving antenna, centre

RM 116 19 55 89 137 40 38 169 18 43

33

Station C Windsock, centre base

Noumea C Station B Glide angle tower, LH edge Transmitter antenna (largest of group), LHE LH receiver antenna, centre Windsock, LHE

SOLOMON ISLANDS Honiara B

Tallest pyramid mast, TDC Spike atop RH tall radio mast Station C LH floodlight pole in front VIP lounge,

LHE at roof level Main aerial on control tower, centre base

Honiara C LH floodlight pole, LHE Main aerial on control tower, centre base Station B Spike atop RH tall radio mast

Santa Cruz A Station B Sign at terminal, crack before'S' in 'SANTA' RHE of terminal roof Windsock to west, centre, at horizon level

Santa Cruz B RHE terminal roof Windsock to west, centre, at horizon level Station A

TUVALU Funafuti C

Terminal building, centre of RH upright Spike atop LH tall radio mast Station D Junction box, LHE

Funafuti D Junction box, same edge as seen from C Terminal building, centre of RH upright Spike atop LH tall radio mast Station C

VANUATU Vila B

LH edge of near white building Top RHE of water tank Red and white pole to NE RH red and white floodlight pole, centre Station C

Vila C Near windsock, centre base Station B Lightpole at terminal, centre

34

241 25 29 246 25 34

61 25 29 RM 87 46 31

132 10 35 161 52 35 278 18 57

39 56 41 129 55 01 303 02 37

335 34 04 RM 352 46 46

36 49 56 RM 45 33 57

123 02 37 128 52 05

74 37 20 161 32 12 163 46 13

RM 248 06 28 89

223 02 55 RM 249 50 44

254 37 20

35 19 45 RM 47 25 36 89

228 18 42 278 14 42

6 32 39 37 51 36

RM 47 37 23 48 18 42

34 01 59 RM 84 30 44 89

114 04 41 131 54 54 297 01 17

RM 115 08 28 117 01 17 128 00 56

Table 6 Observed field values

UT F UT D I UTF

nT d m d m nT

FIJI

Nadi A

17 Jul 89 0438 43258.9 0447 12 46.4 -38 57.0 0453 43261.6 0455 43261.2 0504 12 46.2 -38 57.1 0512 43264.0 2243 43262.8 2253 12 42.8 -38 58.8 2301 43260.6 2302 43260.0 2310 12 42.8 -38 58.7 231843257.9

18 Jul 89 0257 43233.9 0307 12 45.3 -38 58.1 0315 43230.9 0316 43230.9 0325 12 45.8 -38 58.2 033243227.4 210543247.7 2114 12 44.8 -38 59.9 2120 43249.6 212143249.8 2130 12 44.8 -38 59.7 2138 43251.1

19 Jul 89 0023 43260.2 0032 12 42.1 -38 59.8 0038 43257.4 0039 43257.6 0047 12 42.2 -39 00.0 0053 43255.9 0356 43238.0 0404 12 46.4 -38 59.1 0409 43238.3 0410 43238.5 0419 12 46.5 -38 59.1 0425 43239.9 211043274.7 211812 43.8 -38 59.2 212543276.6 2126 43276.9 2134 12 43.8 -38 59.2 2142 43276.3

Nadi A* 18 Jul 89 0213 43247.4 0223 12 43.2 -38 58.9 0230 43241.6

023143241.3 0240 12 43.8 -38 58.9 0247 43237.2

Nadi C

19 Jul 89 015843220.2 0207 12 37.6 -38 57.5 0214 43217.4 0215 43217.4 0223 12 38.0 -38 57.4 0230 43215.3

Nausori A 13 Jul 89 045043178.5 050013 17.0 -39 42.8 050643176.3

0508 43175.7 0514 13 16.9 -39 43.0 0519 43176.9 2230 43178.1 2237 13 14.0 -39 42.6 2243 43178.1 2245 43176.7 2252 13 14.1 -39 42.4 225843176.6

14 Jul 89 0441 43164.0 0448 13 17.1 -39 43.5 0454 43162.7 045643162.4 050213 17.0 -3943.4 050843161.3 2045 43182.5 2052 13 15.2 -39 42.5 2058 43182.3 2100 43182.3 2106 13 15.2 -39 42.3 2112 43283.6

15 Jul 89 0149 43172.8 0158 13 16.5 -39 42.4 0204 43172.4 0206 43171.8 0213 13 16.9 -39 42.4 0220 43169.4 043943165.9 04451317.5 -39 42.1 045043166.6 0451 43165.9 0456 13 17.4 -3942.7 0502 43165.1 1934 43174.1 1942 13 15.8 -39 42.3 1948 43174.6 1949 43174.8 1955 13 15.5 -39 42.2 2001 43176.0

KIRIBATI

Tarawa B

3 Jul 89

4 Jul 89

UT F

nT UT D I lITF

d m d m nT

0346 34750.8 0407 10 22.0 -4 34.7 0417 34744.5 0418 34744.2 0429 10 22.2 -4 35.0 0437 34738.3 214534740.6 22041017.8 -435.6 2212 34744.4 2213 34744.5 22241017.1 -435.2 223234747.8 0428 34749.8 0440 10 21.6 -4 36.3 0449 34748.6 0450 34748.9 0500 10 21.7 -4 36.6 050834747.6 213634767.7 21461020.9 -4 36.5 215534772.3 215634772.7 2206 10 20.8 -4 36.4 2214 34779.7

5 Jul a9 0511 34771.7 0521 10 22.3 -4 34.4 052934766.3

Tarawa B*

0530 34765.9 0540 10 22.4 -4 34.6 0547 34761.8 195734753.6 20061024.5 -437.2 201334747.5 2014 34747.5 2022 10 24.2 -4 37.4 2030 34753.9

5 Jul 89 2204 34765.1 2213 10 20.6 -4 35.3 2221 34765.3

Tarawa C

5 Jul 89 012034822.1 01321017.4 -436.3 014034820.1 0141 34821.0 0150 10 17.8 -4 36.5 0158 34829.5

Tarawa D

5 Jul 89 0401 34828.0 0413 10 20.2 -4 35.6 0421 34820.9 0422 34820.4 0430 10 20.3 -4 35.8 0438 34814.6

NOltIlea B

5 Jun 89 0452 48414.4 0503 13 01.0 -48 10.2 0510 48415.2 0511 48415.0 05181300.7 -48 10.4 052548415.0 2233 48420.2 2244 12 56.4 -48 09.2 2251 48418.7 2253 48418.4 2301 12 55.9 -48 09.2 2308 48418.2

6 Jun 89 032848410.8 03401300.6 -48 09.5 034948407.7 0351 48408.0 0402 13 01.0 -48 09.6 0412 48404.6 0450 48396.1 0502 13 01.6 -48 10.8 0509 48395.7 051048395.8 05191301.3 -48 10.8 052648397.7 2213 48437.0 2224 12 56.8 -48 08.3 2231 48435.3 2232 48435.4 2241 12 56.4 -48 08.3 2248 48434.4 2341 48445.6 2355 12 55.5 -48 07.1

Nausori A* 7 Jun 89 0002 48443.0 15 Jul 89 201343175.7 201913 15.3 -3942.1 202543175.3 000348443.0 0010 12 56.1 -48 07.2 001648438.6

202643174.8 203213 14.8 -39 42.0 203843177.5

Nausori B 15 Jul 89 0254 43145.9 0301 13 09.1 -39 42.7 0307 43144.1

0309 43144.4 0316 13 09.2 -39 42.7 0323 43143.8

Suva Vou A

14 Jul 89 224643395.2 2257 13 07.2 -39 41.2 230343392.1 230543395.4 2312 13 07.0 -39 41.0 231843393.6

35

0227 48388.0 0235 12 59.5 -48 12.6 0241 48382.9 0242 48383.0 0249 12 59.4 -48 12.5 0257 48381.1 0301 48380.6 0309 12 59.5 -48 12.2 0316 48384.0 031748383.7 032512 59.8 -48 12.3 033248383.8 2210 48401. 2 2219 12 56.2 -48 11.1 2226 48401. 8 2227 48402.1 2235 12 56.0 -48 11.4 2242 48402.2

8 Jun 89 0507 48386.2 0516 13 01.0 -48 12.0 0523 48388.6 0524 48388.4 0537 13 00.8 -48 11.8 0544 48391.8 221648435.3 222512 57.2 -48 08.7 223248429.6 2233 48429.7 2241 12 56.4 -48 08.0 2248 48434.9

NOltIlea B"

8 Jun 89 2258 48438.1 2306 12 56.0 -4807.0 2313 48435.1 2314 48435.3 2322 12 55.6 -48 07.3 2331 48430.4

NOltIlea C

5 Jun 89 2346 48353.8 2357 12 52.7 -48 09.7 6 Jun 89 0004 48352.7

0007 48352.8 0014 12 52.8 -48 09.6 0022 48351.8

lIT F lIT D I lITF

nT d m d m nT

Honiara B

19 Jun 89 2351 41267.3

20 Jun 89 0004 10 36.3 -30 33.4 0013 41266.6

043641267.3 0448 9 36.6 -30 33.7 0457 41268.0

045941267.4 0510 9 37.0 -30 34.1 0519 41264.1

2150 41266.6 2202 9 38.4 -30 33.6 2210 41259.7

2211 41259.9 2221 9 38.4 -30 33.6 2230 41260.0

21 Jun 89 0643 41247.1 0654 9 38.4 -3034.2 0701 41245.1

205241255.9 2101 9 38.2 -30 33.0 2108 41255.7

22 Jun 89 0207 41292.0 0216 9 34.8 -30 31.7 0223 41292.6

0224 41292.1 0232 9 34.5 -30 31.6 0239 41293.4

0509 41266.3 0517 9 38.5 -30 32.8 0524 41263.0

0525 41263.1 0532 9 38.9 -30 33.1 0540 41261.6

0541 41262.3 0549 9 39.2 -30 32.8 0556 41262.4

0557 41261.9 0604 9 39.3 -30 33.2 0611 41260.0

2054 41276.1 2103 939.3 -30 33.2 2111 41275.4

2112 41275.5 2121 9 39.3 -30 33.2 2128 41274.6

Honiara C

22 Jun 89 030741303.7 0316 930.1 -30 25.6 032341302.6

0324 41302.7 0331 9 30.5 -30 25.5 0338 41301.2

Santa Cruz Is A 24 Jun 89 0613 41292.2 0624 10 18.8 -31 15.0 0632 41291.4

0634 41291.0 0642 10 18.7 -31 15.2 0649 41289.7

1930 41288.5 1939 10 19.5 -31 15.4 1946 41292.5

1947 41292.2 1955 10 19.9 -31 15.4 2002 41295.0

25 Jun 89 060141255.4 06081019.5 -31 15.3 0615 41257.0

061741257.2 06241019.7 -3115.4 063041259.1

192641297.9 1934 10 19.2 -31 15.1 194141299.7

1943 41300.5 1951 10 19.5 -31 15.2 1959 41304.2

26 Jun 89 0546 41284.0 0555 10 18.5 -31 14.9 0602 41283.5

0604 41283.9 0612 10 18.6 -31 14.7 0618 41282.4

2056 41304.3 2105 10 18.5 -31 15.5 2112 41306.6

211441307.1 21211018.1 -31 15.7 212741308.0

Santa Cruz A* 26 Jun 89 2155 41311.3 2202 10 17.4 -31 15.5 2208 41312.7

Santa Cruz B 25 Jun 89 2034 41331.8 2044 10 23.0 -31 17.6 2051 41335.1

2055 41335.4 2104 10 22.5 -31 17.8 2111 41336.9

TIlVALU

Funafuti C

7 Jul 89 0514 37094.7 0532 1126.6 -21 42.7 054137090.6

0542 37090.1 0551 1126.7 -21 42.9 055837086.1

2242 37138.3 2252 11 24.2 -21 41.4 2259 37139.3

2300 37139.2 2308 11 23.9 -21 41.8 2315 37140.9

8 Jul 89 0133 37138.8 0142 11 23.4 -21 41. 4 0150 37135.7

0151 37135.3 0159 1123.7 -21 41.9 0207 37131.0

0338 37113.5 0347 11 25.6 -21 41.9 0354 37109.8

0355 37109.6 0403 11 25.9 -21 42.2 0410 37105.8

1817 37103.5 1827 11 26.0 -21 42.7 1836 37109.3

1837 37109.6 1849 11 26.5 -21 42.8 1858 37112.9

9 Jul 89 0431 37102.7 0439 1127.5 -21 42.0 044637100.6

0447 37100.0 0455 11 27.0 -21 42.0 050237098.5

1815 37114.6 1833 11 26.6 -21 42.0 1841 37119.1

1842 37120.8 1852 11 26.8 -21 42.3 1901 37123.9

UT F UT D I UTF nT d m d m nT

Funafuti C(cont.)

10 Jul 89 021037152.7 02181124.2 -2140.7 022537149.8

0226 37149.8 0234 11 24.8 -21 40.9 0242 37146.5

0350 37130.9 0359 11 26.0 -21 41.8 0407 37126.0

0408 37125.5 0416 1126.4 -21 41.7 0424 37120.2

1819 37095.6 1830 11 26.6 -21 43.0 1840 37099.5

184137099.5 185011 27.0 -21 43.2 185837101.0

Funafuti C*

10 Jul 89 0301 37141.2 0309 11 25.2 -21 41.2 0317 37136.3

0318 37137.0 0326 11 25.5 -21 41.3 0334 37133.0

Funafuti D 8 Jul 89 0232 37136.9 0245 11 27.3 -21 38.2 0252 37129.4

0253 37130.1 0301 11 27.5 -21 38.2 0309 37126.3

VANUATU

VilaB 12 Jun 89 0432 45264.2 0442 11 53.2 -42 06.5 0452 45258.4

045345258.4 050211 53.0 -4207.1 051045254.2

2203 45295.8 2222 11 50.2 -42 05.5 2231 45295.7

2232 45296.0 2243 11 50.0 -42 05.0 2252 45298.2

13 Jun 89 0223 45301.9 0233 11 50.9 -42 04.4 0241 45297.1

0242 45297.0 0252 11 51. 7 -42 04.7 0300 45291. 3

0514 45274.4 0522 11 52.9 -42 07.0 0529 45273.7

053045273.3 053811 52.9 -42 07.2 054545272.3

2223 45307.9 2235 11 48.6 -42 04.4 2248 45310.7

2249 45311.1 2259 11 48.8 -42 04.8 2310 45309.9

14 Jun 89 0002 45306.1 0017 11 47.9 -42 04.6 0029 45304.6

0030 45304.6 0040 11 48.0 -42 04.6 0049 45303.8

0409 45265.6 0421 11 53.1 -42 06.4 0429 45259.3

043045259.2 044011 53.3 -42 07.2 044945254.7

2144 45283.3 2155 11 50.1 -42 07.0 2203 45286.9

2204 45287.1 2214 11 50.6 -42 06.6 2211 45287.1

15 Jun 89 0053 45285.1 0101 11 49.2 -42 07.8 010845277.6

0109 45278.2 0117 11 49.3 -42 08.2 0124 45273.3

0338 45260.9 0347 11 51. 4 -42 07.9 0354 45260.2

035545260.1 040411 52.0 -42 07.7 0411 45258.9

215545265.6 2203 1149.4 -42 07.0 220945266.0

2210 45266.1 2220 11 48.8 -42 06.9 2226 45265.8

Vila B"

12 Jun 89 2339 45304.8 2349 11 49.8 -42 04.0 2357 45307.9

2358 45307.5

13 Jun 89

Vila C

13 Jun 89

000811 49.7 -42 03.8 001645310.2

033745326.6 034811 59.7 -42 10.4 035545322.3

0356 45322.3 0407 11 59.4 -42 10.8 0414 45320.0

Note * indicates observations made at height of Askania tripod

36

Table 7 Preliminary mean hourly values

DECLINATIOO EAST MEAN B:XlRLY VALUES PRELIMINARY

UT 0 1 2 345 678 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

J1.IDe 1989 1 2 3 4 5

6 7 8 9

10

11 12 13 14 15

16 17 18 19 20 21 22 23

24 25

D

Q

Nounea

565 578 592 568 586 593 564 569 580

Port Vila

480 497 494 495 507 481 477 488 488 493 508

Q Honiara

12 Deg +tabular values In O.lmin

601 591 588 585 582 579 577 578 580 582 582 585 586 583 583 583 575 565 557

604 612 608 597 607 601 601 613 605

517 531 529 527 527 526 511 527 527 511 524 519

594 590 585 594 588 579 591 588 582

524 523 517 515 513 514 524 526 523 507 506 493

579 574 574 574 575 553 580 578 577

576 578 581 561 572 578 578 580 580

583 585 586 582 586 588 582 587 587

11 Deg +tabular values in O.lmin

510 509 504 513 507 497 511 497 494 500 492 485

501 499 496 500 503 507 486 497 496 503 503 504 490 491 485 492 498 503 488 491 488 497 504 499


583 585 587 587 587 581 587 591 588

508 518 523 500 508 507 506 521 527 504 513 514

577 566 559 570 564 564 586 565 561

515 503 502 501 491 485 507 496 486 502

356 352 355 357 373 385 379 375 372 371 368 366 368 374 373 378 378 375 376 384 399 387 381 367 Q 353 347 345 355 376 392 388 380 377 374 373 373 376 377 379 381 383 383 382 382 385 384 374 368 Q 362 351 341 348 367 381 387 384 381 375 374 375 374 375 376 375 378 380 383 383 393 395 Q

Santa Cruz Is 10 Deg +tabular values In O.lmin

169 171 171 173 165 166 171 168 171 171 174 176 174 184 193 184 175 158 144 149 156 166 177 188 193 187 182 178 175 175 174 177 180 180 182 183 182 187 191 175 159 145

26 129 129 150 167 183 184 187 192 187 183 178 178 178 176 179 182 186 186 190 192 194 175 27 28 29 30

July 1989 1 D Tar<Ma 10 Deg +tabular values in O.lmin 2 3 4 5

6 7 8 9

Q Q D

174 193 164 182 197 186 185 194

F\mafuti

209 216 216 215 210 208 208 207 209 209 208 207 206 213 215 215 211 208 205 205 205 205 207 206 210 218 225 226 216 212 209 207 205 207 209 210

207 209 210 211 214 199 207 208 210 209 218 218 212 215 218 226 243 238


184 167 161 210 204 193 220 200

264 271 273 270 268 265 263 262 263 255 250 253 255 255 260 264 257 252 247 241 Q 236 236 242 248 255 259 257 254 253 258 263 259 260 257 257 259 259 260 263 270 263 257 254 248

246 249 263 268 271 264 261 259 255 256 257 251 250 251 252 253 254 256 259 262 254 240 229 228 10 230 233 242 250 259 262 257 250 251 252 261 263 262 262 264 266 267 266 270

11 12 13 14 15

16 17 18 19 20

21 22 23 24 25

Q Nausori 13 Deg +tabular values In O.lmin

Q

141 145 149 148 147 150 153 154 155 156 157 156 157 159 162 154 141 139 139 138 146 159 166 168 162 159 156 155 153 154 153 153 156 158 157 159 162 165 165 155 149 144 138 141 155 168 174 172 163 157 155 153 152 152 149 151 151 150 152 153 153 153 156 149

Nadi 12 Deg +tabular values in O.lmin

D 466 463 462 460 458 455 454 452 450 452 452 453 454 454 458 463 456 446 439 438 D 440 439 442 457 466 462 454 450 447 447 443 441 440 441 440 444 446 448 449 454 452 445 437 427

424 424 434 445 448 445 441 437 435 435 434 435 433 435 433 435 437 438 438 444 438 429 425 421

26 D 27 28 29 30 31 37

583 581 583

505 504

373 374

174

205

255 254

155

446 435

B:RrzrnI'AL INTENSITY MEAN lDlRLY VALUES Hill..ll-flNARY

UT o 1 2 345 678 9 ill 11 U ~ " 15 16 17 18 19 20 21 22 23 24

Jt.me 1989 1 2 3 4 5

6 7 8 9

10

11 U 13 14 15

16 17 18 19 20

21 22 23

24 25

D

Q

NOLtll9a 32000. +tabular values in nT.

287 291 291 292 286 284 292 295 294 296 296 303 308 307 3U 316 317 306 302

299 302 301 294 276 273 319 269 245 239 229 215 268 264 266 264 256 252

279 280 275 204 222 225 260 276 281

274 277 283 223 200 189 283 281 279

287 289 291 216 236 236 281 282 282

292 296 300 237 242 248 282 282 286

Port Vila 33000. +tabular values in nT.

597 596 635 630 618 624 627 626 586 570 553

596 583 562 551 553 568 571 568 565 566 571 573 600 587 580 579 582 585 569 567 572 575 572 575 604 573 556 554 552 535 530 543 559 549 546 564 557 563 557 546 539 543 532 530 552 551 551 548

569 571 575 576 578 586 557 566 571 548 553 561

303 308 321 252254 260 302 316 345

579 586 599 601 601 606 574 583 587 561 565 576

328 324 339 266 272 274 326 322 336

609 618 631 623 631 631 588 593 591 575

Q Honiara 35000. +tabular values in nT.

536 537 543 538 536 528 529 524 531 529 516 486 460 464 476 485 488 491 494 515 533 536 526 529

Q 540 548 546 538 528 521 515 511 509 508 507 507 504 505 508 507 510 5U 513 518 524 530 553 555 Q 554 556 546 528 518 514 513 5U 5U 510 514 514 5U 515 519 519 520 521 527 529 538 538 Q

Santa C= Is 35000. +tabular values in nT.

298 298 291 286 292 294 271 262 271 275 276 281 285 292 302 304 310 310 311 307 305 294 282 267 267 272 266 263 268 269 270 275 277 280 281 287 295 303 3U 3U 316 321

26 326 322 316 3~ 307 294 284 275 270 276 275 263 268 276 277 279 281 284 290 298 306 308 27 28 29 30

July 1989 1 D Tarawa 34000. +tabular values in nT. 2 3 4 5

6 7 8 9

10

11 U 13 14 15

16 17 18 19 20

21 22 23 24 25

Q 659 655 640 626 616 607 601 603 602 603 603 603 600 601 599 596 598 600 606 614 627 637 644 Q 648 640 636 630 631 631 625 617 615 615 616 616 615 615 617 619 618 618 618 622 633 650 671 677 D 673 673 687 690 675 655 641 635 631 627 624 625 622 620 616 615 618 615 616 636 639 636 653

F\mafuti 34000. +tabular values in nT.

471 465 454 459 462 459 459 459 461 452 455 451 456 459 462 471 479 489 504 5U Q 510 506 493 479 470 463 469 473 471 463 464 462 466 472 469 465 465 468 471 480 488 495 500 505

505 493 483 465 466 466 467 471 469 469 465 461 461 466 469 472 477 478 486 499 517 532 540 543 539 530 518 501 486 462 461 473 467 452 454 455 461 459 457 456 452 454 463

Q Nausori

2U 205 195 203 211 205 206 205 201 199 201 203 204 211 206 205 204 205 204 205 203 204

Nadi

33000. +tabular values in nT.

206 205 203 204 206 207 203 203 206 207 205 205 202 200 197 201 203 200

206 208 211 210 217 220 204 206 208 215 221 222 201 203 203 207 215 220


220 216 216 223 223 220

Q D 639 637 626 609 615 623 623 613 621 627 627 627 624 622 631 640 641 633 626 624 D 624 619 610 604 587 579 595 600 598 589 585 591 594 593 590 588 596 601 605 610 610 613 619 624

615 610 606 610 608 606 608 611 6~ 6U 613 6U 615 617 619 622 623 624 627 638 646 641 641 641

26 D 27 28 29 30 31 38

295 241 286

594 573

514

522

288

629

478 484

209

601 620

UT 0 1 2 345 678

VERTICAL INTENSITY MEAN !nIRLY VALUES

9 10 11 12 13 14 15 16 17 PRELIMINARY

18 19 20 21 22 23 24

Jtme 1989 1 2 3 4 5

6 7 8 9

10

11 12 13 14 15

16 17 18 19 20

21 22 23

24 25 26 27 28 29 30

Nottnea -36000. -tabular values in nT.

75 76 78 78 79 80 80 80 81 81 82 82 81 79 79 79 77 73 69

63 64 64 63 65 68 72 73 76 76 75 76 76 77 77 76 76 77 76 75 72 72 70 65 D 68 75 72 70 76 79 81 77 80 83 87 83 84 84 84 84 84 83 82 81 78 77 76 73

69 63 61 62 65 69 73 74 77 78 79 78 80 79 79 81 81 81 79 78 74 75 65 61

Q

Port Vila -30000. -tabular values innT.

351 346 344 347 355 363 365 365 368 372 372 372 371 370 370 370 368 367 363 359 360 357 354 355 354 351 352 356 359 358 355 350 345 350 357 374 371 369 364 359 360

361 359 362 361 362 368 365 366 368

368 370 369 370 368 366 371 372 368

367 365 364 370 370 368 370 370 372

361359357 363 364 361 371 365 364

358 356 355 359 355 357 365 363 360

356 359 357 368 369 374 361

Q Honiara -20000. -tabular values in nT.

979 978 978 979 980 981 978 981 980 980 982 986 987 989 986 986 987 985 985 983 981 983 981 977

Q 974 969 971 969 966 970 976 978 980 981 982 983 984 986 986 988 988 988 989 989 984 981 978 976 Q 975 975 974 973 972 974 978 979 981 981 980 980 981 984 985 987 987 990 992 986 985 987 Q

Santa Cruz Is -21000. -tabular values in nT.

415 419 422 424 426 425 423 423 422 424 409 403 404 405 405 407 416 420 423 427 427 425 426 423 435 427 414 408 408 411 416 416 421 426 430 429 431 429 427

422 424 425 427 424 425 431 430 429 423 425 426 427 425 430 437 442 441 426 427 426 426 429 429 437

July 1989 1 D Tarawa -2700. -tabular values in nT. 2 3 4 5

6 7 8 9

Q

Q D

59 56 75 82 87 88 88 86

FUnafuti

63 71 77 93 91 88 79 76 77

81 85 87 86 84 86 79 81 83

88 89 91 88 88 89 86 90 88

90 92 90 89 89 89 88 93 91

-13000. -tabular values in nT.

91 91 94 88 90 91 93 93 93

93 89 84 93 94 93 97 99 94

80 76 76 90 91 90 90 80

720 720 720 719 720 720 721 721 722 724 725 725 726 726 727 727 726 726 726 726 Q 724 724 725 724 724 723 723 722 722 722 722 723 724 724 724 724 725 726 726 726 724 724 723 722

722 723 722 722 722 721 721 721 722 723 723 725 726 726 726 727 726 727 728 729 727 725 723 724 10 725 726 727 726 726 725 724 724 724 724 722 722 723 724 724 724 725 725 725

11 Q 12 13 14 15

Q Nadi -27000. -tabular values in nT.

16 17 18 19

D 190 199 204 209 208 207 211 214 214 213 212 212 213 212 203 201 210 218 218 207 D 208 208 198 188 196 210 213 215 217 221 220 222 224 223 226 221 216 215 214 208 210 215 219 222

20

21 22 23 24 25

26 27 28 29 30 31

D

221 217 204 196 203 212 212 214 213 216 216 217 217 220 221 219 217 219 215 207 215 223 225 222

39

72 79 73

360 362

982

980

422

89

72 72

214 215

UT 0 1 2 345 678

TOTAL INTENSIlY MEAN EnlRLY VALUES

9 10 11 12 13 14 15 16 17 ffiELlMINARY

18 19 20 21 22 23 24

June 1989 1 2 3 4 5

6 7 8 9

10

11 12 13 14 15

16 17 18 19 20

21 22 23

24 25 26 27 28

29 30

Nounea 48000. +tabular values in nT.

416 419 421 421 418 415 418 421 421 421 421 424 427 427 428 430 430 422 418

416 418 417 412 402 400 408 411 409 408 411 415 418 420 421 422 425 426 427 429 434 437 435 440 D 432 408 389 382 379 371 366 376 379 379 369 357 377 390 392 392 394 397 399 400 402 404 404 406

398 394 395 393 390 391 399 411 416 418 418 419 417 418 417 417 418 420 428 436 452 448 448 431

Q

Port Vila

282 279 276 267 254 314 312 302 287 278 275 305 307 304 282 260 252 287 274 258 258 258 254

248251 262 275 276 274 252 252 241 249242244


265264263 269267271 238 249 258 237 238 252

264 266 266 273 271 272 252252262 252 253 249

264 264 265 270 271 276 256 261 262 248 250 255

269 271 281 284 282 286 264 267 271 254 256 262

290 297 305 301 309 309 281 287 290 265

Q Honiara 41000. +tabular values in nT.

266 269 277 273 270 265 264 259 262 261 249 225 205 208 217 224 225 227 229 245 260 265 258 259

Q 268 273 273 266 254 250 248 245 242 242 241 242 240 240 243 244 245 247 249 251 255 258 267 274 Q 281 283 285 285 269 255 251 250 248 248 249 251 249 250 254 254 253 255 257 260 264 266 Q

Santa Cruz Is 41000. +tabular values in nT.

291 287 294 294 272 265 273 276 277 281 286 291 301 308 314 314 312 303 297 287 277 263 263 270 265 266 273 274 273 276 277 278 281 287 293 300 310 318 322 324 329 322 310 301 293 284 281 277 274 275 275 264 268 273 273 274 276 279 285 293 300 308

July 1989 1 D Tarawa 34000. +tabular values in nT. 2 3 4 5

6 7 8 9

10

11 12 13 14 15

Q Q

D

775 770 762 757 752 789 788 801

Funafuti

756 743 731 746 750 748 803 787 767

721 714 714 715 716 715 715 714 713 711 710 711 740 731 729 729 729 729 729 728 729 730 730 730 753 745 740 737 734 733 731 729 724 723 727 726


714 720 727 730 734 747 727 748 753

739 747 756 766 783 790 751 766

96 91 82 83 84 83 83 84 Q 142 139 128 115 103 99 102 100 96 94 95 95

136 127 117 101 102 98 101 102 101 101 96 92 166 160 150 134 117 94 96 104 97 91 89 89

89 89 89 91 92 94 98 109 115 123 136 144 97 102 100 98 100 103 111 119 123 128 130 134 94 97 99 102 107 111 118 131 145 157 163 166 97 93 93 91 89 89 98

Q Nausori 43000. +tabular values in nT.

174 166 159 162 166 167 165 164 176 174 169 168 169 166 163 164 167 167 167 167 170 171 169 168 167 168 170 176 182 182 185 186 183 180 174 169 165 168 166 168 168 169 168 165 163 166 167 165 165 165 165 167 175 179

Nadi 43000. +tabular values in nT. 16 Q 17 18 19 20

21 22 23 24 25

D 261 265 260 248 253 259 260 255 260 263 264 263 260 267 276 274 D 254 253 242 229 221 222 233 237 236 230 229 232 234 234 231 228 233 235 236 238 242 249 257 261

257 250 243 239 240 243 244 247 248 247 247 249 250 251 252 252 252 253 253 258 269 272 274 273

26 D 27 28 29 30 31 40

419 389 416

284 267

248

252

287

743

111 115

172

237 253

Table 8 Adopted station values and secular variation at epoch 1990.0

Station D H Z F I X Y deg nT nT nT deg nT nT

Funafuti C 11.423 34465 -13706 37090 - 21. 711 33782 6826 Honiara B 9.637 35516 -20980 41250 -31. 758 35015 5945 Nadi A 12.745 33617 -27195 43240 -38.989 32789 7416 Nausori A 13.220 33206 -27565 43156 -39.697 32326 7594 Noumea B 12.977 32295 -36050 48400 -48.162 31470 7252 Port Vila B 11.857 33598 -30346 45274 -42.097 32882 6903 Santa Cruz Is A 10.302 35272 -21430 41272 -31. 273 34704 6308 Tarawa B 10.728 34625 -2736 34733 -4.612 34020 6446

dD dH dZ dF dI dX dY min nT nT nT min nT nT

Funafuti C -0.5 -19.8 15.1 -24.0 0.62 -18.5 -8.4 Honiara B 0.9 -9.2 5.7 -10.8 0.00 -10.6 7.7 Nadi A 0.0 -19.6 34.2 -28.2 1.13 -19.2 -3.9 Nausori A -3.8 -15.6 27.3 -29.5 0.88 -6.7 -39.6 Noumea B 1.2 -18.3 18.8 -26.2 -0.08 -20.3 6.5 Port Vila B 1.1 -17.5 18.8 -25.5 0.17 -19.3 6.9 Santa Cruz Is A 0.6 -14.7 15.0 -19.6 0.43 -15.6 3.6 Tarawa B 4.3 -14.1 -0.11 -21. 8 39.4

Table 9 Secular variation derived from IGRF85 model at epoch 1990.0, and residuals

Station dD dH dZ dF dI dX dY min nT nT nT min nT nT

Funafuti C -1. 6 -17.2 5.4 -17.9 -0.14 -19.6 -13.5 Honiara B -0.6 -8.0 9.5 -11.7 0.34 -8.9 4.7 Nadi A 0.6 -22.1 8.8 -22.7 -0.57 -20.4 -10.3 Nausori A -0.6 -23.7 8.2 -23.5 -0.69 -21. 8 -10.9 Noumea B 0.5 -14.6 11.1 -18.0 -0.25 -15.3 1.6 Port Vila B 0.1 -13.5 11.8 -17.9 -0.02 -13 .4 -2.0 Santa Cruz Is A 0.1 -8.9 13.2 -14.5 0.55 -8.9 -1.1 Tarawa B -1. 3 -10.6 16.3 -12.0 1. 51 -8.1 -14.7

Residuals (FO - IGRF) Station dD dH dZ dF dI dX dY

min nT nT nT min nT nT

Funafuti C 1.1 -2.6 9.7 -6.1 0.76 l.1 5.1 Honiara B l.5 -l. 2 -3.8 0.9 -0.34 -l. 7 3.0 Nadi A -0.6 2.5 25.4 -5.5 l. 70 l.2 6.4 Nausori A -3.2 8.1 19.1 -6.0 1. 57 15.1 -28.7 Noumea B 0.7 -3.7 7.7 -8.2 0.17 -5.0 4.9 Port Vila B l.0 -4.0 7.0 -7.6 0.19 -5.9 8.9 Santa Cruz Is A 0.5 -5.8 1.8 -5.1 -0.12 -6.7 4.7 Tarawa B 5.6 -3.5 -1. 62 -13.7 54.1

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Table 10 Station differences

Station 1 Station 2 Station 1 - 2 D H Z F

Funafuti C Funafuti c* -0.3 1 3 0 Funafuti C Funafuti D -2.6 -25 34 -8 Honiara B Honiara B+ 0.1 -9 4 -9 Honiara B Honiara C 4.8 -60 -39 -17 Nadi A Nadi A* 0.8 -2 1 -1 Nadi A Nadi C 5.5 4 38 26 Nausori A Nausori A* 0.0 1 2 Nausori A Nausori B 8.5 15 20 Nausori A Suva Vou A 7.0 -210 173 Noumea B Noumea B* 0.6 9 1 2 Noumea B Noumea C 3.5 48 45 -37 Santa Cruz A Santa Cruz A* -0.8 -3 0 -1 Santa Cruz A Santa Cruz B -4.0 -6 -36 -21 Tarawa B Tarawa B* 0.0 3 0 4 Tarawa B Tarawa C 0.9 -39 6 -38 Tarawa B Tarawa D 1.3 -32 -12 -29 Vila B Vila B* 0.2 -2 1 2 Vila B Vila C -6.4 8 -74 -42

Note The symbol + means after concreting * observations made at QHM tripod height (1.22 m)

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bureau of mineral resources, geology geophysicsnausori, fiji nadi, fiji 5. data reductions 6....

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