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IAG PAIGH NIMA

GEOCENTRIC REFERENCE SYSTEMFOR THE AMERICAS

SIRGAS

NEWSLETTER # 7

December 2002

IAG PAIGH NIMA

SIRGAS Project Netwsletter # 7 Page 1

TABLE OF CONTENTS

EDITORIAL

MINUTES OF THE COMMITTEE MEETING, HELD ON OCTOBER 21 AND22, 2002, IN SANTIAGO, CHILE

ANNEXES TO THE MINUTES

I: STATUS ON THE INTEGRATION OF THE SOUTH AMERICAN COUNTRIESTO SIRGAS (WG II “GEOCENTRIC DATUM”)

II: PRESENTATION OF THE SIRGAS 2000 GPS CAMPAIGN RESULTS

III: ITRFYY AND ITS GEODETIC APPLICATION, BY MUNEENDRA KUMAR

PRESENTATIONS OF THE WG III “VERTICAL DATUM”

IV: INTRODUCTIONV: URGENT NEED OF A MODERN VERTICAL REFERENCE

SYSTEMVI: COMPUTATION OF GEOPOTENTIAL NUMBERS AND

PHYSICAL HEIGHTSVII: REFERENCE SURFACE: CONSIDERATIONS REGARDING W0VIII: FUTURE ACTIVITIES

IX: STATUTE OF THE SIRGAS PROJECT

X: LIST OF THE SANTIAGO MEETING ATTENDEES

XI: PICTURES OF THE MEETING

IAG PAIGH NIMA


EDITORIAL

I am glad to introduce to readers the seventh edition of the SIRGAS Newsletter. This editionintegrally covers the last project meeting, held on October 21 and 22, in Santiago, Chile.During this meeting, important discussions and resolutions were taken, which are described inthis newsletter, with emphasis to those related to the results of the SIRGAS 2000 GPScampaign and to the new project statute.

I would like to take this opportunity to wish readers, colleagues of the SIRGAS communityand their families a Merry Christmas and a peaceful, healthy and successful New Year.

Luiz Paulo Souto FortesPresident of the SIRGAS Committee

IAG PAIGH NIMA


MINUTES OF THE COMMITTEE MEETING, HELD ON OCTOBER 21 AND 22,2002, DURING THE VII INTERNATIONAL CONGRESS OF EARTH SCIENCES, INSANTIAGO, CHILE

October 21st

1. Opening (L. Fortes, President of the Committee)

The president of the Committee highlighted the financial support given by the InternationalAssociation of Geodesy (IAG), decisive for holding the meeting. The Pan-AmericanInstitute of Geography and History (PAIGH), which had approved funds for the project in2002, could not honor this commitment due to financial difficulties that it is currently facing.Therefore IAG responded to our last minute request, enabling the attendance of eightparticipants of seven countries of South America, which was decisive for the success of themeeting.

2. Status on the integration of the South American countries to SIRGAS (R. Barriga,President of the WG II) (Annex I)

3. Presentation of the SIRGAS 2000 GPS campaign results by the processing centers

3.1 IBGE (S. Costa) (Annex II)3.2 DGFI (K. Kanniuth)

The coordinates obtained in the individual solutions of each processing center (DGFI withBernese, DGFI with GIPSY and IBGE with Bernese) shown a consistency between eachother of about 5 mm in the horizontal components and 7.5 mm in the vertical component.

Resolution: The SIRGAS Committee decided that the final solution of the SIRGAS2000 GPS campaign will be generated by the combination of three solutions: DGFI´s,using the Bernese software; DGFI´s, using the GIPSY software; and IBGE´s, usingthe Bernese software.

4. Combination of the processing centers´ results (H. Drewes/K. Kanniuth/S. Costa)

4.1 Combination strategy and connection to ITRF2000

M. Kumar, from NIMA, presented the following issue: the ITRF solutions are generatedusing the tide-free system, which is not realistic and contradicts the IAG Resolution 16 of1983 (Annex III)

Resolution: To keep using the tide-free system in the SIRGAS 2000 results and toformally suggest to IAG to manage with the International Earth Rotation Service(IERS) the solution of this issue.

IAG PAIGH NIMA


4.2 Determination of velocities

According to H. Drewes, it is not enough to consider the results of the SIRGAS 1995 and2000 campaigns for the determination of the SIRGAS stations velocities.

Resolution: The SIRGAS Committee approves H. Drewes´ proposal of consideringthe observations of permanent GPS stations and of geodynamic campaigns, inaddition to the results of the SIRGAS 1995 and 2000 campaigns, for thedetermination of the velocity field of the South American continent.

4.3 Final results (coordinates and velocities)

Resolution: The SIRGAS Committee accepts in advance as official the finalcombined results of the SIRGAS 2000 GPS campaign, to be generated by theprocessing centers in near future.

Resolution: The SIRGAS Committee defines the date of December 20, 2002, as thedeadline for the processing centers to release the final combined results of theSIRGAS 2000 GPS campaign.

Resolution: The SIRGAS Committee defines the date of March 28, 2003, as thedeadline for DGFI to release the results of the velocity field for the South Americancontinent.

Resolution: The procedures to generate the official results of the SIRGAS 2000 GPScampaign will be described in a final report, similarly to that released during theIAG Scientific Assembly, held in Rio de Janeiro, in 1997.

Resolution: The SIRGAS Committee proposes to include in the SIRGAS 2000 GPScampaign final report a special acknowledgment to the processing centers – DGFIand IBGE – by the enormous efforts carried out and by the excellence of the resultsobtained.

5. Use of the SIRGAS 2000 final results (H. Drewes, Representative of IAG)

Resolution: The SIRGAS Committee proposes to include in the SIRGAS 2000 GPScampaign final report detailed instructions about how to use the campaign finalresults.

It was recommended that, for countries that have not adopted yet SIRGAS 1995 asreference system, they should adopt the system based on the SIRGAS 2000 results,reference epoch 2000.4.

IAG PAIGH NIMA


6. Presentation and start of discussion of the new statute proposal (C. Brunini, SubstituteRepresentative of Argentina)

October 22nd

7. Presentations of the Working Group III “Vertical Datum” (L. Sanchez, President ofWG III, and H. Drewes, Representative of IAG)

7.1 Introduction (Annex IV)7.2 Urgent need of a modern vertical reference system (Annex V)7.3 Computation of geopotential numbers and physical heights (Annex VI)7.4 Reference surface: considerations regarding W0 (Annex VII)7.5 Future activities (Annex VIII), recommending to countries:

• Geodetic leveling of the SIRGAS2000 stations• Connection of leveling networks between neighboring countries• Identification and typing of all leveling lines that connect SIRGAS2000 stations• Typing of the national leveling networks• Identification of the network nodes• UNIFIED determination of the quasi-geoid• Determination of the sea surface topography (SSTop) (GPS positioning of tide

gauges)

The WG III president offered support to the member countries of the SIRGAS Committeeregarding the computation of geopotential numbers and help with parallel tasks. It isemphasized that the height differences to be used in computations are the observed ones,WITHOUT any error distribution or adjustment.

8. Continuation of the discussion on the new statute proposal (L. Fortes and C. Brunini)

Resolution: The SIRGAS Committee approves the new project Statute,corresponding to the version originally proposed by the representation of Argentina,with the modifications discussed during the meeting in Santiago del Chile.

With the approval of the Statute (Annex IX), the substitute representative of Argentina inthe Committee, Claudio Brunini, proposed the names of Luiz Paulo Souto Fortes, fromIBGE/Brazil, and Eduardo Andrés Lauría, from IGM/Argentina, respectively for presidentand vice-president of the project for the next term (2003-2007). The current president ofthe SIRGAS Committee will contact all countries embraced by the project in order toconfirm the names of the representatives in the Committee and, consequently, to definethe necessary quorum for electing the new project authorities. This election will be carriedout by electronic mail and the elected authorities will be installed in office in July 2003, atthe General Assembly of the International Association of Geodesy.

IAG PAIGH NIMA


9. Closing (L. Fortes)

Resolution: The SIRGAS Committee acknowledges the Instituto Geográfico Militarof Chile for the excellent organization of the meeting and for the support to theCommittee members.

10. List of attendees (Annex X)

11. Pictures of the meeting (Annex XI)

IAG PAIGH NIMA

ANNEX I

STATUS ON THE INTEGRATION OF THE SOUTH AMERICAN COUNTRIES TOSIRGAS (WG II “GEOCENTRIC DATUM”)

(included in the complete version of this Newsletter, available athttp://www1.ibge.gov.br/home/geografia/geodesico/sirgas/principal.htm)

http://www1.ibge.gov.br/home/geografia/geodesico/sirgas/principal.htm

fortes

(included in the complete version of this Newsletter, available at http://www1.ibge.gov.br/home/geografia/geodesico/sirgas/principal.htm)

GRUPO DE TRABAJO IIDATUM GEOCENTRICOGRUPO DE TRABAJO IIDATUM GEOCENTRICO

TCL. R. Barriga V.

email : [email protected]

GRUPO DE TRABAJO II“DATUM GEOCENTRICO”GRUPO DE TRABAJO II

“DATUM GEOCENTRICO”

MISION : Establecer un Datum Geocéntrico mediante laextensión de la Red GPS SIRGAS a través dela integración de las “Redes Geodésicas” de cada uno de los países sudamericanos partici-pantes en el Proyecto.

“SITUACION INDIVIDUAL DE CADA PAIS”

ARGENTINAARGENTINA

RESPONSABLES : Claudio Brunini, Juan Moirano U. Nac. De la Plata. Rubén Rodríguez Eduardo Lauría, Instituto Geográfico Militar.

MEDICIONES DE TERRENO : 136 estaciones Red POSGAR 98 109 puntos en común con POSGAR 94

PROCES. DE LOS DATOS : Universidad Nacional de la Plata - DGFI. Software BERNESE 3.5

AVANCE : Recientemente el Subcomité de Geodesia ha recomendado el uso del nuevo marco de referencia POSGAR 98 para las aplicaciones geodésicas de alta precisión que se desarrollen en el futuro, aunque mantendrá por un tiempo más la vigencia de POSGAR 94. POSGAR 98, época 1995.4

CONTRIBUCION A SIRGAS 2000 : 20 estaciones.

RED DE ARGENTINARED DE ARGENTINA

BOLIVIABOLIVIA

RESPONSABLES : Instituto Geográfico Militar

MEDICIONES DE TERRENO : Existen 2 Redes de control GPS - Red geodésica Fundamental clase A - Red Minera clase B.

PROCES. DE LOS DATOS : Instituto Geográfico Militar - UNLP Software BERNESE.

CONTRIBUCION A SIRGAS 2000 : 9 estaciones. .

“SIN ANTECEDENTES ACTUALES”

ECUADORECUADOR

RESPONSABLES : Departamento de Geodesia del instituto

Geográfico Militar

MEDICIONES DE TERRENO : 135 estaciones medidas durante 1994, 1996 y 1998.

PROCES. DE LOS DATOS : En DGFI, Munich, Software BERNESE 4.0.

AVANCE : Obtención de coordenadas enlazadas a SIRGAS, época 1995.4.

CONTRIBUCION A SIRGAS 2000 : 8 estaciones. PUNTOS AMBOS SISTEMAS : 42 puntos en común entre PSAD56 y

SIRGAS para la determinación de paráme- tros locales de transformación...

RED DEL ECUADORRED DEL ECUADOR

BRASILBRASIL

RESPONSABLES : Sonia María Alves Costa - IBGE Instituto Brasileiro de Geografía y Estadística.

CONTRIBUCION A SIRGAS : 22 estaciones SIRGAS, 14 son de la Red de Monitoreo Contínuo.

PROCES. DE LOS DATOS : IBGE, Software BERNESE 4.0.

AVANCE : En Octubre del año 2000 el IBGE organizó y coordinó el primer Seminario para visualizar la adopción de el nuevo Marco de Referencia Geodésico. En el año 2005, Brasil pretende adoptar el SIRGAS oficialmente.


RED DEL BRASILRED DEL BRASIL

-70 -65 -60 -55 -50 -45 -40 -35 -30

-30

-25

-20

-15

-10

-5

0

5

GPSSIRGAS/RBMC

Cuiaba

Manaus

Imperatriz

Brasília

Fortaleza

Crato Recife

SalvadorBomJesus

Porto Alegre

Curitiba

P.PrudenteViçosa

R.Janeiro

Rede Nacional GPS ano 2002

Sta. Maria

CHILECHILE

RESPONSABLES : Instituto Geográfico Militar.

MEDICIONES DE TERRENO : 260 puntos Nueva Red Geodésica Nacional. 133 puntos conectados a la antigua Red.

PROCES. DE LOS DATOS : Instituto Geográfico Militar Software BERNESE 4.0

AVANCE : Coordenadas preliminares ITRF 2000, a la espera de ajuste final a SIRGAS 2000. Se estima que en el año 2005 se adoptará oficialmente SIRGAS en Chile.

CONTRIBUCION A SIRGAS 2000 : 20 estaciones, incluyendo 8 estaciones GPS permanentes y 5 mareógrafos.

RED CHILENARED CHILENA

COLOMBIACOLOMBIA

RESPONSABLES : Laura Sánchez Instituto Geográfico Agustín Codazzi.

MEDICIONES DE TERRENO : La Red MAGNA consta de 60 estaciones GPS de las cuales 16 corresponden a la Red CASA (Red Geodinámica para Centro y Sur de América).

PROCES. DE LOS DATOS : I. G. Agustín Codazzi - DGFI. Software BERNESE 4.0

AVANCE : La Red MAGNA y en consecuencia SIRGAS fue adoptado como sistema oficial en Colombia desde 1998. Se están definiendo los estándares de geo- posicionamiento a nivel nacional, dentro de la normativa ISO9001.


RED DE COLOMBIARED DE COLOMBIA

AGUAC

VALLED

BQUIL

TUNJA

TUMAC

YARUM

TIBU

CARTA

CUCUT

GUARI

BUCAR

IPIAL

MAICA

MOMPO

RIONE

RIOHA

QUIBD

MONTE

NAZARPTBOL

PTBER

PASTO

POPAY

VILLA

SARAV

YOPAL

IBAGE

NEIVA

SMART

LETIC

MOCOA

PTINI

PTCAR

OROCU

PEDRE

PTLEG

MITU

SFELI

ARAUC

BACOM

CHORR

ARARA

FLORE

SJGUA

CRNOR

MANIZ

GUAPI

PLATO

SOLAN

COROZ

CAUCA

SROQU

CALI

BOGOT

BTURA

TURBO

BOSCO

TULUA

80° 79° 78° 77° 76° 75° 74° 73° 72° 71° 70° 69° 68° 67° 66° 5°

4°

3°

2°

1°

0°

1°

2°

3°

4°

5°

6°

7°

8°

9°

10°

11°

12°

13°

81.41° 81.39° 81.37° 81.35° 13.32°

13.34°

13.36°

13.38°

13.40°

81.75° 81.73° 81.71° 81.69°12.48°

12.50°

12.52°

12.54°

12.56°

12.58°

12.60°

SAN ANDRES, PROVIDENCIA Y SANTA CATALINA

MALPELO

SANAN

1994

1995

1997

1994 - 1995

1994 - 1997

1994 - 1995 - 1997

PARAGUAYPARAGUAY

RESPONSABLES : Servicio Geográfico Militar

MEDICIONES DE TERRENO : 165 puntos medidos de la Red Geodésica primaria en 1992.

PROCES. DE LOS DATOS : Servicio Geográfico Militar y por el NIMA.

CONTRIBUCION A SIRGAS 2000 : 1 Estación.


PERUPERU

RESPONSABLES : Instituto Geográfico Nacional

MEDICIONES DE TERRENO : 165 puntos medidos de la Red Geodésica primaria en 1992.

PROCES. DE LOS DATOS : Servicio Geográfico Militar y por el NIMA.



URUGUAYURUGUAY

RESPONSABLES : Servicio Geográfico Nacional y el Instituto de Agrimensura.



VENEZUELAVENEZUELA

RESPONSABLES : José Napoleón Hernández Instituto Geográfico de Venezuela Simón Bolivar

MEDICIONES DE TERRENO : 156 estaciones entre 1995 y 2000.

PROCES. DE LOS DATOS : Software BERNESE

AVANCE : Venezuela posee 210 vértices integrados a SIRGAS, disponibles y publicados. Así mismo se encuentran 500 vértices totalmente cal- culados, en fase de edición de descripciones, accesos y monografías. Venezuela oficialmente ha adoptado a SIRGAS como nuevo Sistema de Referencia.


RED DE VENEZUELARED DE VENEZUELA

GRUPO DE TRABAJO IIDATUM GEOCENTRICOGRUPO DE TRABAJO IIDATUM GEOCENTRICO

TCL. R. Barriga V.

email : [email protected]

IAG PAIGH NIMA

ANNEX II

PRESENTATION OF THE SIRGAS 2000 GPS CAMPAIGN RESULTS



fortes


RESULTS OF THE SIRGAS 2000 GPSRESULTS OF THE SIRGAS 2000 GPSCAMPAIGNCAMPAIGN

Klaus Kaniuth - Deutsches GeodatischesForschungsinstitut - DGFISonia Costa - Brazilian Institute of Geography andStatistics - IBGE

International Symposium of the IAGRecent Crustal Deformation in South America and SurroundingArea, october, 2002

Maintenance of SIRGAS reference frame; Define a unique height reference system forthe Americas.

2

RESULTS OF THE SIRGAS 2000 GPS CAMPAIGNRESULTS OF THE SIRGAS 2000 GPS CAMPAIGN

Goals of SIRGAS2000 campaignGoals of SIRGAS2000 campaign

Tide gauges, which define the vertical datum ofthe leveling networks in each country;Other tide gauges (countries with longextension of coast);Stations of leveling networks at the bordersbetween neighboring countries;Stations participating of SIRGAS95 network.

3


Selection criteria of stationsSelection criteria of stations

The data on each station was organized in 24 hoursperiod and converted to RINEX format;

Data collection rate was 15 and 30 (IGS and NGS) sec. ; Double frequencies receivers preferably with choke ringantenna or receivers without choke ring antenna, thatones recognized by IGS;

Station information's: station name, observationsessions, antenna height (slant/vertical) andantenna/receiver type (IGS identification).

4


Campaign Specifications andCampaign Specifications andEquipmentEquipment

5


Processing Information'sProcessing Information's

Orbits and ERP: Combined IGS (SP3 files); Coordinates of the reference stations : ITRF97, epoch2000.3;

Antenna phase center offset and variation: Informationobtained at IGS and NGS;

Antenna heights were corrected to ARP (AntennaReference Point).

Software: Bernese , version 4.2

6


Processing Strategies - IBGEProcessing Strategies - IBGESolutions Options Mode Daily sessions Observations double differences, observable L3 (ionosphere

free, linear combination of L1 and L2) Strategy forming baselines

OBS-MAX

Sampling rate 30 sec. Elevation cut off angle 10 degrees Elevation weighting Cos(z) Troposphere model (A PRIORI)

Not applied

Trop. zenith delay Every 2 hours (12 corrections) Mapping function Niell (dry component) Ionosfere model Not applied Ambiguity resolution QIF (Quasi Ionosfere Free) + GIMs\CODE maps Ocean Loading Not applied Reference Stations AREQ, AMC2, ALBH, AOML, BRAZ, CRO1,

FORT, LPGS, OHIG, KOUR, SANT, WES2, CORD, JAMA and UNSA

7


CombinationCombinationof Solutionsof Solutions/ IBGE/ IBGE

Divided in 9blocks, with about22 stations each;

3 IGS stationsmake the linkbetween blocks;

Final dailysolutions weresaved as removableconstraints

8


Link Stations between blocksLink Stations between blocks

N N1 N2 C S S1 S2 S3 S4WES2 WES2 AOML JAMA CART BOGA BRAZ UNSA LPGSAMC2 AMC2 INEG CRO1 FORT IMPZ ZAMO LPGS SANTALBH ALBH BRMU ESTI KOUR BRAZ UNSA CHAM CORD

BRMU JAMA CART BOGA AREQ LPGS CORUAOML CRO1 FORT IMPZ ZAMO CHAM SANTINEG ESTI KOUR BRAZ UNSA CORU CORD

NetworkConfiguration

and BlocksDivision - IBGE -


STATIONS PROBLEMS AND CHANGESSTATIONS PROBLEMS AND CHANGES

10


– UCOR (Argentina) and NPAC (Guatemala) were not used inprocessing.

– CART (Colombia) is a different station from campaign 1995, buthas the same identification for SIRGAS2000.

– BATL (Ecuador) was identified as GALA (Ecuador) in campaign1995. Consequently, GALA in campaign 2000 (IGS station) is adifferent station from campaign 1995.

– MANU (Brazil) station was identified as MANA in campaign 1995.– L10B (Argentina) was identified as LO10 in campaign 1995.– CACH (Brazil) station from campaign 1995 was destroyed and

changed to CAC1.– BOGT (Colombia) station in 1995 campaign, was changed to

BOGA.– Stations YACA (Uruguay), ASUN (Paraguay), were not occupied in

SIRGAS 2000 campaign.

DATA PROBLEMSDATA PROBLEMS

11


–– Too many cycles slipsToo many cycles slips:: VIMS (U.S.)/day 133, YBHB(U.S.)/day 134, TEGU (Honduras)/ day131, CHIQ (Bolivia)/days 131-132.

–– Few quantity of data:Few quantity of data: KAMA (Venezuela)/day132 (4 hours ofdata), ARIC/day 135 (1:30 of data), LOTE (Argentina)/day 136one hour of data), RIOP (Ecuador)/day 134 (some minutes ofdata), NPRI (U.S.)/day 132 (less than 6 hours of data), AMC2(U.S.)/day 137 (less than 6 hours of data), CA00/day 137.

–– Data from wrong date:Data from wrong date: MERI (Mexico)/day 138 (data from1980), CHI3 (Mexico)/day 135, OAXA (Mexico)/day 135, RBLS(Argentina)/day 139.

–– DataData excluded because of observations problems excluded because of observations problems:: ANTF(Chile)/days 136, 137, 138, 139 and 140.

Preliminary combination:Preliminary combination: ADDNEQ removable constraints: removable constraints: CRO1, KOUR, FORT, ALBH,

WES2, BRAZ, AREQ, LPGS, SANT, OHIG and CORD.

Stations excluded from final results: Stations excluded from final results: UCOR, NPAC andANTO.

Number of stations processedNumber of stations processed = 182Stations with less than 5 days of solutions:Stations with less than 5 days of solutions: CHAJ (3

days), JUNQ (3 days), LOTE (4 days), ELEN (2 day) andRIOP (3 days).

Checking accuracy with ITRF2000: Stations, which have residuals higher than 20 mm are:Stations, which have residuals higher than 20 mm are:

GALA, CRO1, INEG, SIO3.

12


ResultsResults


Accuracy of solution / IBGEAccuracy of solution / IBGEITRF2000 RESIDUALS

-30

-20

-10

0

10

20

30A

LBH

ALG

O

AM

C2

AO

ML

AR

EQ

AS

HV

BO

MJ

BR

AZ

BR

MU

CH

A1

CH

UR

CO

RD

CR

O1

CU

IB

DR

AO

DU

BO

EIS

L

FLIN

FOR

T

GA

L1

GA

LA

GO

DE

HO

LB

IGM

0

STATIONS

MM

NORTHEASTUP

ITRF2000 RESIDUALS

-60

-40

-20

0

20

40

60

IMP

Z

INE

G

JAM

A

KO

UR

LPG

S

MA

NU

OH

IG

PA

RA

PU

R3

RIO

G

RIO

P

SA

NT

SC

H2

SIO

3

SO

L1

STJ

O

UE

PP

US

NA

US

NO

VB

CA

VIC

O

VIM

S

WE

S2

WH

IT

WIL

L

YE

LL

STATIONS

MM

NORTHEASTUP

Consistency of daily solutions /Consistency of daily solutions /IBGEIBGE


14

–The stations, which have up component RMS higherthan 20 mm are: IMPZ and TALA

–EISL station presented higher RMS in the internalsolution

Consistency of Block solutionsConsistency of Block solutions


15

UNWEIGHTED RMS RESIDUALS - NORTH COMPONENT

02

468

10

1214

131 132 133 134 135 136 137 138 139 140DAYS

mili

me

ter SIRGASN

SIRGASN1SIRGASN2SIRGASCSIRGASSSIRGASS1SIRGASS2SIRGASS3SIRGASS4

UNWEIGHTED RMS RESIDUALS - EAST COMPONENT

02468

101214

131 132 133 134 135 136 137 138 139 140DAYS

mili

met

ers

SIRGASNSIRGASN1SIRGASN2SIRGASCSIRGASSSIRGASS1SIRGASS2SIRGASS3SIRGASS4

UNWEIGHTED RMS RESIDUALS - UP COMPONENT

02468

1012141618

131 132 133 134 135 136 137 138 139 140DAYS

mili

met

ers


Consistency of Block solutionsConsistency of Block solutions


16

WEIGHTED RMS RESIDUALS - NORTH COMPONENT

02468

101214

131 132 133 134 135 136 137 138 139 140DAYS

mili

met

erSIRGASNSIRGASN1SIRGASN2SIRGASCSIRGASSSIRGASS1SIRGASS2SIRGASS3SIRGASS4

WEIGHTED RMS RESIDUALS - EAST COMPONENT

02468

101214

131 132 133 134 135 136 137 138 139 140DAYS

mili

met

er


WEIGHTED RMS RESIDUALS - UP COMPONENT

02468

101214

131 132 133 134 135 136 137 138 139 140DAYS

mili

met

ers


IAG PAIGH NIMA

ANNEX III

ITRFYY AND ITS GEODETIC APPLICATION

BY MUNEENDRA KUMAR

ITRFyy AND ITS GEODETIC APPLICATION

By

Muneendra KumarNational Imagery and Mapping Agency

Bethesda MD 20816-5003 (USA)

Abstract

The International Terrestrial Reference Frame (ITRF) is a realizationof the International Terrestrial Reference System (ITRS). Since itsfirst realization in 1988, there have been many variations and additionsin data types and changes in computations of ITRF. Between ITRF88 andITRF97, the reference epochs have also changed three times. Manytechnical notes from the International Earth Rotation Service (IERS) areavailable. These notes explain and provide in great details all thetechnical complexities of different realizations, which have been updateevery year between 1988 and 1994. After 1994, the ITRF 96 and 97 are thetwo latest solutions.

This paper intends to present and clarify the technicalinterpretation of the ITRF realization and its definition for thepractical geodesists who want to update the geodetic infrastructure of anation, region, continent, or for the world. The attempt here is toinclude significant details and explanations to provide a clear andconsistent interpretation.

1. INTRODUCTION

International Earth Rotation Service (IERS), since it’s founding in1988, has been updating ITRS with its realizations as ITRF. Firstsolution was ITRF88, which then was followed yearly by ITRF89, 90, 91,92, 93, and 94. After this, we got two more solutions, viz., ITRF96 andITRF97.

ITRF realization consists in a set of station Cartesian coordinates,a velocity field, and a full variance-covariance matrix (Silard et al,1998). The direction of the IERS Reference Pole (IRP) and ReferenceMeridian (IRM) corresponds to the Bureau International de L’Heure (BIH)Conventional Terrestrial System (CTS) Pole and Zero Meridian (McCarthy,1996).

Between 1988 and 1993, ITRFyy (where “yy” corresponds to the year inwhich it was realized) solution was obtained by a combination of alldata submitted to the beginning of yy+1 (Boucher et al, 1997). Here, thereference epoch was 1988.0. The ITRF94 was then defined to the referenceepoch 1993.0.

Then, the reference frame definition (origin, scale, orientation, andtime evolution) was achieved in such a way that ITRF96 is in the samesystem as ITRF94 (Boucher et al, 1997). This was followed by a combinedsolution for ITRF96 and ITRF97 with 1997.0 as reference epoch.

This paper provides and clarifies the technical details concerningthe different ITRFs and their reference epochs with the each periodicIERS solution. A suggested approach is also included for geodetic usewhen updating national, regional, continental, and/or global geodeticsystem(s) or datum(s).

Published in the Proceedings of the IAG 2001 Scientific Assembly, 2-7 September 2001, Budapest, Hungary

2. INTERNATIONAL TERRESTRIAL REFERENCE FRAME (ITRF)

ITRF is a realization of the International Terrestrial ReferenceSystem (ITRS). The orientation of its axes is consistent with the Bureau deL’Heure (BIH) Conventional Terrestrial System (CTS) at the epoch 1984.0, inaccordance with the resolution of the International Union of Geodesy andGeophysics (IUGG) and International Astronomical Union (IAU).

The orientation of the system is such that it has no residualrotational horizontal velocity relative to the Earth’s crust. Theconstruction of the ITRF is based on the combination of sets of stationcoordinates and velocities derived from observations from Very LongBaseline Interferometry (VLBI), Satellite Laser Ranging (SLR), and LunarLaser Ranging (LLR). Data from Global Positioning System (GPS) wasintroduced in 1991 and from Doppler Orbitography and Radio-positioningIntegrated by Satellite (DORIS) in 1994.

ITRFyy represents a solution, which is based on the data sets thatare available till the end of year “yy” and is performed in the year“yy+1”. From the first ITRF88 the solutions are available for 89, 90, 91,92, 93, 94, 96, 97, and a combined solution for 96 and 97.

3. ITRF COMPUTATIONS

The procedure is in sequential steps.

(1) First step involves a reduction of coordinates for theparticipating stations to a common reference epoch t0

using their respective velocity models. These velocitymodels are either based on fixed tectonic plate motion orestimated velocity fields.

The computations (XS, XS’)t0 are done separately for eachsystem “S”, e.g., VLBI.

(2) Second step involves a least-squares estimation at thereference epoch “t0” the coordinates and velocities forthe ITRFyy of all the stations from all the systems,e.g., VLBI, SLR, LLR, GPS, and DORIS. The model used inthe “combination” solution is based on Euclidiansimilarity of seven parameters:

XS X T1

S DS -R3

S R2

S X

YS = Y + T2

S + R3

S DS R1

S Y (1)

ZS Z t0 T3

S R2

S R1

S DS Z t0

where X,Y,Z are the coordinates of a station at referenceepoch t0 in the ITRFyy, T1

S, T2

S, T3

S, DS, R1

S, R2

S, R3

S arerespectively the three translations, scale factor, and threerotations between the ITRFyy and individual “S” solutions.

(3) The local geodetic survey ties, with their standarddeviations, are used to tie the stations of the differentsystems.

4. ITRF EPOCHS

From the first ITRF88, the reference epochs used to define differentITRF solutions (Altamimi, 2000) are:

ITRF88 to ITRF93 - 1988.0

ITRF94 - 1993.0

ITRF96 - 1993.0

ITRF96 and ITRF97 - 1997.0

ITRF00 - 1997.0

Here, we can interpret that ITRF 89 to ITRF93 represent therealization of ITRF88 with additional data sets in each subsequentsolution. Thus, in real sense, each of the solutions for the years 1988 to1993 only realized the same ITRF.

It is important to note that the combined solution for the ITRF96 andITRF97 was obtained by combining positions and velocities simultaneously.This procedure allowed the use of full variance-covariance matrices of theindividual VLBI, SLR, GPS, and DORIS data solutions. This will allow usersto propagate the 1997.0 positions to any desired epoch. Thus, this approachalso replaced the old ITRF96 as a separate realization.

5. ITRF DEFINITION

Coordinates are defined in a conventional “tide-free” system(APPENDIX

1) where effects of all tidal have been removed. To achieve this, theEquation 6 (Pp. 57, IERS Tech Note 21, 1996) is used.

6. ITRF ORIENTATION AND SCALE

(1) The orientation is defined by adopting IERS Earth OrientationParameters (ERP) at a “reference” epoch (See Section 3).

(2) The orientation of the IERS Reference Pole (IRP) and ReferenceMeridian (IRM) were initially given by the BIH TerrestrialSystem (BTS) 1984.0 (McCarthy, 1996). Subsequently, the IRP andIRM are consistent with the “corresponding” directions of theBTS within 0.005”. Thus, the corresponding BTS for the ITRFsolutions from 1988 to 1993 (Section 4) will then be:

ITRF88 to ITRF93 - BTS 1988.0

Since BIH was replaced by IERS from 1988, the orientations forITRF94, ITRF96, and ITRF97 followed an independent definition.

According to Montag (1997), the IRP and IRM were defined byIERS on the basis of the Conventional International Origin(CIO). However, it is not clear which CIO would have been used.

(3) The scale is obtained by relativistic modeling and isconsistent with the Geocentric Coordinate Time (TCG) for ageocentric local frame (Chapter 11, IERS Tech. Note 21, 1996).

(4) The unit is meter (SI).

The time evolution of the orientation is maintained by using ano-net- rotation condition with regards to the horizontaltectonic motions over the whole Earth.

7. MOVEMENT OF THE GEOCENTER

Recent analysis of SLR and other satellite data has shown that the

coordinates of stations connected to the solid Earth, as realized by theITRF, show variations as compared with the ITRF, which is assumed to befixed to the rigid Easrth’s crust (Montag, 1997). Thus, the origin of theITRF is defined such that the time-dependent translation vector T (from theITRF origin to the instantaneous center of mass of the Earth) is minimum(Montag, 1997).

8. GEODETIC APPLICATION

A. Important Considerations (McCarthy, 1996) -

a. ITRF coordinates are realized in the tide-free system and it isimportant to note that this system is not realistic and the crust can notbe observed.

b. Alternatively, in the zero-tide system, the crust correspondsto the realistic time average which varies because of the action of luni-solar tides.

c. The ITRF coordinates (Section 8.A.a. above) contradicts the IAGResolution 16, adopted at The 1983 General Assembly (APPENDIX 2).

B. Recommendation -

The following steps relate to a 10-day GPS campaign scenario which isobserved from 25 June to 5 July 2001, with mid-epoch of 2001.5.

a. Select the IGS stations, which are to be used as constraints todefine the intended geodetic system.

b. Using the “latest” available ITRF coordinates and velocities,viz., ITRF00 with reference epoch 1997.0, propagate coordinatesof the stations to the mid-epoch 2001.5.

c. To be consistent with the IAG Resolution 16, 1983 (APPENDIX 2),compute the IGS station coordinates to the zero-tideenvironment.

d. Adjust the network using the propagated and restoredcoordinates with the zero-tide effects as constraints withappropriate weights.

The reference frame of the geodetic system can be held fixed till thenext accuracy enhancement. It need not change with each new realization ofan ITRFyy. A reference epoch change would be optional but may not benecessary.

References

Boucher, C. Altamimi, Z., and Sillard, P., 1998. “Results and Analysis ofthe ITRF96”, IERS Technical Note 24, Central Bureau of IERS, Paris, France.

Boucher, C. Altamimi, Z., and Sillard, P., 1999. “The 1997 InternationalTerrestrial Reference Frame (ITRF97)”, 1999, IERS Technical Note 27,Central Bureau of IERS, Paris, France.

Ekman, M., 1989. “Impacts of Geodetic Phenomena on Systems of Height andGravity”, Bull. Geod., 63.

McCarthy, D. D., 1992. “IERS Standards (1992)”, IERS Technical Note 13,Central Bureau of IERS, Paris, France.

McCarthy, D.D., 1996. “IERS Conventions (1996)”, IERS Technical Note 21,Central Bureau of IERS, Paris, France.

Montag, H., 1997. “Zur Definition and Uberwachung der Parameters desInternational Terrestrial Reference Systems ITRF mit besondererBerucksichtigung der Variationen des Geozentrums”, Zeitschrift furVermessungswesen (ZfV), vol. 123, No. 7. (English Translation, NIMA TC-5480, 2000)

Rapp, R. H., 1989. “The Treatment of Permanent Tidal Effects in theAnalysis of Satellite Altimeter Data for Sea Surface Topography”, Ma,Geod., 14.

APPENDIX 1

To account for the effect of the permanent tide, terrestrialreference frames may be defined:

Zero-tide – Permanent or “zero frequency tide” is retained.

The crust corresponds to the realistic time average,which varies with the luni-solar tides.

Tide-free – All effects of permanent tide are removed.

This is not realistic since the crust can not beobserved.

Mean-tide – This a “tide-free” system except the geoid is modeledwith permanent tide effects.

References

McCarthy, Dennis D., “IERS Technical Note 21”, 1996.

Ekman, M., 1989. “Impacts of Geodetic Phenomena on Systems of Height andGravity”, Bull. Geod., 63.

Rapp, R. H., 1989. “The Treatment of Permanent Tidal Effects in theAnalysis of Satellite Altimeter Data for Sea Surface Topography”, Ma,Geod., 14.

Poutanen, M., Vermeer, M., and Mekinen, J., 1996. “The Permanent Tide inGPS Positioning”, Journal. Of GEOD.

APPENDIX 2

IAG Resolution No. 16, 19831

The International Association of Geodesy (IAG),

recognizing the need for the uniform treatment of tidal correctionsto various geodetic quantities such as gravity and station positions, and

considering the reports of the Standard Earth Tide Committee andS.S.G. 2.55,

recommends that :

1. the rigid Earth model be the Cartwright – Taylor - Eddenmodel with additional constants specified by theInternational Centre for Earth Tides,

2. the elastic Earth model be that described by Wahr using the1066 A model Earth of Gilbert and Dziewonski,

3. the indirect effect due the permanent yielding of the Earthbe not removed,

and

4. ocean loading effects be calculated using the tidal chartsand data produced by Schwiderski as working standards.

1 Text obtained from IAG.

IAG PAIGH NIMA

ANNEX IV

PRESENTATIONS OF THE WG III “VERTICAL DATUM”:

INTRODUCTION



fortes


GTIII-SIRGAS: Dátum Vertical

Santiago de Chile, Octubre 2002

• Sep 1997: Adopción oficial de las coordenadas SIRGAS y creación del GTIII-SIRGAS: Dátum vertical. Presidente: R. Luz

• Ago 1998: Taller de trabajo: consideraciones teóricas para la definición del nuevo sistema vertical:

+ alturas elipsoidales+ un tipo de alturas físicas+ superfcies de referencia correspondientes+ realización mediante un marco de referencia (h, C, N)

• Jul 1999: Documento técnico sobre los fundamentos teóricos del sistema vertical, BIVAS/BIDAS, planificación campaña GPS mayo 2000

• May 2000: Campaña GPS: realización de la componente geométrica del nuevo sistema vertical: 184 estaciones, 115 en América del Sur

• Feb 2001: “Sistema de referencia geocéntrico para las Américas“, recomendación oficial para la adopción de alturas normales

• Sep 2001: Preprocesamiento de las campaña 2000. Presidente GTIII-SIRGAS: Laura Sánchez

Componentes del nuevo sistema vertical


1. Alturas: Elipsoidales (componente geométrica)Normales (componente física)

2. Superficies de referencia:Elipsoide GRS80 (Elipsoidales) Cuasigeoide (Normales)

3. Marco de referencia:Estaciones SIRGAS95Mareógrafosestaciones fronterizas

4. Mantenimiento del sistema de referencia:Cambios del marco de referencia a través del tiempo

HN= h - ζHN = C/γmHN = Σdn + kN

nivel de referencia (W0)nivel medio del mar

coordenadas SIRGASnivelación geométricavalor de gravedad

Actividades recientes en los países de América del Sur relacionadas con el GTIII-SIRGAS (I)


➤ Diagnóstico de los sistemas de alturas existentes✔ The vertical reference system in the Argentine Republic (Lauría, et al. 2001)✔ Brazilian first order levelling network (Luz, et al. 2001)✔ The vertical geodetic network in Chile (Maturana et al.2001)✔ Considerations of different height systems in Venezuela (Wildermann, et al. 2001)✔ Vertical height system in Colombia (Sánchez 2001)✔ Reportes al GTIII: Argentina, Brasil, Bolivia, Chile, Colombia, Ecuador, Perú, Uruguay

➤ Determinación de la componente geométrica (alturas elipsoidales)✔ Procesamiento SIRGAS2000: Kaniuth (DGFI), Costa (IBGE)

➤ Superficies de referencia: Cuasi-geoide✔ Subcomisión de la IAG para la determinación del geoide en América del Sur✔ New results in the determination of the geoid model in Argentina (Pacino, et al. 2001)✔ Data collecting and processing for a quasi-geoid determination in Brazil (Blitzkow, et al. 2001)✔ Improving a quasi-geoid model in Colombia (Martínez, et al, 2001)✔ The vertical datum and local geoid models in Uruguay (Subiza, et al. 2001)✔ Current status of geoid calculation in Venezuela (Hoyer, et al. 2001)✔ A reference suface for the unified height system in the northern part of South America (Sánchez, 2001)

Actividades recientes en los países de América del Sur relacionadas con el GTIII-SIRGAS (II)


➤ Topografía y variación de la superficie del mar✔ Correlation between multi-mission altimeter time series and tide gauge registration in the Caribbean sea (Acu�a, et al. 2001)✔ Monitoring tide gauges benchmarks in Argentina by GPS (Natali, et al. 2001)✔ Connecting sea level and height systems along the coast of South America (Acu�a, et al. 2001)✔ Local effects in the Brazilian vertical datum (de Freitas, et al. 2001)✔ Acompa�amiento del dátum altimétrico Imbituba a través de las redes altimétrica y mareográfica del sistema geodésico brasile�o (Luz et al. 2001)✔ Vertical crustal movement of tide gauges in Argentina (Natali, et al. 2002)

➤ Cálculo de números geopotenciales✔ Approach to the new vertical reference system for Colombia (Sánchez & Martínez 2001)✔ Comparisson of the classical and the modern vertical reference system in Colombia (Sánchez & Drewes 2001)✔ Hacia una nueva referencia vertical en Argentina (Moirano et al. 2002)

➤ Nivel del cuasi-geoide (W0)✔ Associated problems to link the South American vertical networks and possible approaches to face them (de Freitas, et al. 2001)✔ Realisation of the Soth American reference system (Sánchez & Drewes 2002)

GTIII-SIRGAS: Taller de trabajo, Santiago de Chile, octubre 2002


➨ Importancia de la definición de un sistema vertical moderno de referencia

➨ Cálculo de número geopotenciales

➨ Comentarios sobre el nivel de la superficie de referencia física: Cuasi-geoide

➨ Actividades inmediatas .... URGENTES!!!

IAG PAIGH NIMA

ANNEX V


URGENT NEED OF A MODERN VERTICAL REFERENCE SYSTEM



fortes


The Urgent Need of Modern Vertical Reference Systems

• Classical height reference systems shall refer to the geoid as anequipotential surface of the Earth’s gravity field.

• They are connected to the mean sea level (MSL) during anarbitrarily chosen epoch at a selected tide gauge.

• The mean sea level of a tide gauge does not refer to the geoid- because of the geographic variations of sea level (SSTop).

Status of classical height systems (1)

Sea SurfaceTopography

Around SouthAmerica

Bosch 2000

Status of Classical Height Systems (1)



• The mean sea level of a tide gauge does not refer to the geoid- because of the geographic variations of sea level (SSTop)

- because of temporal variations of mean sea level

Variation of TideGauge Records

Examples:

Mar del Plata (Arg.) -0,2 mm/aBuenaventura (Col.) 6,1 mm/aLa Libertad (Ecu.) -1,0 mm/aLa Guaira (Ven.) 2,5 mm/a




• The mean sea level of a tide gauge does not refer to the geoid- because of the geographic variations of sea level (SSTop)- because of temporal variations of mean sea level

Consequences• All height systems referring to different tide gauges (i.e.,

national height systems) provide a different height level.


• Heights are extended from the tide gauges to the continentalinterior by spirit levelling.

• Spirit levelling does not refer to the geoid, but it has to becorrected for gravity effects.

Heights from Spirit Levelling

Orthometric Heights and Normal Heights

Orthometric heights:H = (W0 - WP) / gm

gm can only be determinedusing a hypothesis on thegravity gradient dg/dH

Normal heights:HN = (W0 - WP) / γm

γm can be computed from thenormal gravity field of thereference ellipsoid (GRS80)

Modern Height Systems

• Nowadays heights are determined with modern geodeticspace techniques, e.g., GPS.

• The primary height system is geometrically defined by areference ellipsoid.

Ellipsoidal Heights

Combination of Modern Heights and Classical Heights

To transfer modern heights (h) to classical height systems they have tobe reduced because of geoid undulations (N) or height anomalies (ζ)

H = h - N HN = h - ζ

hh

This requires the determination of geoid or cuasigeoid, respectively.Most global gravity field models refer more closely to the cuasigeoidthan to the geoid (because they do not reduce local gravity gradients).

Conclusion

• Height determination will be done in future primarily by GPS.

• To combine ellipsoidal heights from GPS with classical heightsfrom spirit levelling we have to reduce both of them to the sameheight reference system.

• Reduction of ellipsoidal heights (from GPS) to normal heights ispossible without hypothesis and in a unique global referenceframe by height anomalies from global cuasigeoid computations.

• To apply “GPS levelling” correctly it is necessary to reduce allnational height systems from levelled heights to normal heights!

IAG PAIGH NIMA

ANNEX VI


COMPUTATION OF GEOPOTENTIAL NUMBERS AND PHYSICAL HEIGHTS



fortes


Cálculo de números geopotenciales

GTIII-SIRGAS Santiago de Chile, Octubre 2002

∫ ∑ ∆⋅=⋅=−=p

0 iiip0 ngdngWWC

1

2

3dn1

dn2

A

B

dn1 ≠ dn2

Línea de la plomada (dirección del vector de la gravedad)

Supercie Equipotencial

GeoidW = W0

W = W2

W = W1

( ) ( ) ( ) ( )

2gg

g

ngngngngC

1A1A

B3B3232312121A1AB

+=

∆⋅+∆⋅+∆⋅+∆⋅=



Información requerida:

☛ Diferencias de nivel medidas (errores sistemáticos)

☛ Distancia (en km) entre los puntos nivelados

☛ Año de nivelación

☛ Valores de gravedad real en cada punto de nivelación




Diferencias de nivel medidas (errores sistemáticos)

εRεV

εR≠εV

εRεV

εR=εV

Refracción




Distancia (en km) entre los puntos nivelados

[ ]

[ ]km2n

n

kmn

d16/1

m1

p

dmm4m

==

=

∆∆

∆

Error medio (Ponderación)




Año de nivelación

A

A

B

BC

C

C

D

D

D

E

E

195019501962

1985 1985

1978

1992

Nivelaciones en diferentes épocas

Cambios en los desniveles medidos entre los mismos puntos:errores de observación?movimiento vertical?

Reducción de las observaciones a una sóla época?




Valores de gravedad real en cada punto de nivelación

A

B

CD

E

Disponibilidad de valores de gravedad

Interpolación de los valores de gravedad observada!!


Precisión requerida en la interpolación de gravedadpara el cálculo de números geopotenciales

∑ ∆= ngC 2g

22n

22C mnmgm ∆+= ∆⇒ [ ]kmn dmm4m ±=∆⇒

Σ∆n [m] mg[mGal] mg[mGal] d = 1km d = 2km

10 40 55 20 20 28 30 13 19 40 10 14 50 8 11 70 6 8 100 4 6 200 2 3 500 1 1,51000 0,5 0,82000 0,3 0,54000 0,1 0,2


Recomendaciones referentes a la interpolación de gravedadpara el cálculo de números geopotenciales

⇒ La gravedad varía con la altura y con las masas

⇒ Anomalía de Bouguer!!∆gBouguer = gobs + CAL + Cbouguer - γ

⇒ gobs = ∆gBouguer - CAL -CBouguer + γ CAL = 0,3086 H CBouguer = -2πGρ H ≈ - 0,1119 H γ = Gravedad teórica sobre GRS80

⇒ Precisión de la latitud para el cálculo de γ:Interpolación de gravedad: ~2” ≈ 60 mAlturas normales: ~0,5”≈ 15 m

∑∆=punto

mareógrafo

nH⇒ Altura de los puntos a interpolar:


Actividades URGENTES relacionadas con el cálculo de números geopotenciales

Digitación (formato digital) de las nivelaciones nacionales

→ nombre del punto→ desnivel medido→ distancia [km] entre ellos→ año de observación→ coordenadas geodésicas (latitud y longitud)→ valor de gravedad observado o interpolado a partir de Anomalía Simple de Bouguer


Actividades INMEDIATAS relacionadas con el cálculo de números geopotenciales

Identificación de los nodos de las redes de nivelación nacionales


Actividades RE-URGENTES relacionadas con el cálculo de números geopotenciales

Identificación y digitación de todas las líneas de nivelación que conectan las estaciones SIRGAS2000:(SIRGAS95, mareógrafos y estaciones fronterizas)


Y después de los números geopotenciales.....

Definición de los dátum clásicos:Superficie del mar = Geoide

Elipsoide

Geoide Nivel medio del mar

H

h

N

Colom

bia

Brasil

Buenaventura Imbituba


Y después de los números geopotenciales.....

Sistema vertical modeno:Superficie del mar ≠ Geoide

⇒ Cúal puede ser la referencia para ∆W?⇒ Es necesario definir un W0?

Elipsoide

Geoide

NMM (1942 - 1963)

Cbra

Ccol

∆W

Colom

bia

Brasil

BuenaventuraImbituba

NMM (1949 - 1957)W0 Col

W0 BraSSTop (Col) SSTop (Bra)

IAG PAIGH NIMA

ANNEX VII


REFERENCE SURFACE: CONSIDERATIONS REGARDING W0



fortes


The Realisation of the Height Reference Surface- W0 Considerations -

• Earth gravity models, such as EGM96, provide a sphericalharmonic expansion of the gravity potential:

( ) ( ) 22

01 2

1cossincos1 pPmSmC

r

a

r

GMW

l

mlmlmlm

l

l

ωθλλ +

+

+= ∑∑

=

∞

=

• The radius r, for which to apply this expansion, may arbitrarily be chosen, e.g., the semimajor axis a of a best-fitting ellipsoid.

• Therefore, the geoid is not unequivocally prescribed but has to be defined by a certain value a, or equivalently by W0.

• After the definition of Listing (1873) the equipotential surface W = W0 of the geoid coincides with the mean sea level. This is not automatically realised by using an Earth gravity model.

General Procedure of W0 Determination

From satellite altimetry we get the three-dimensional positionof the sea surface. This surface differs from the geoid becauseof sea surface topography (SSTop).

ellipsoidsea surface

geoid


Geoid W0

Sea Surface WSS

rkri

- We determine the gravitypotential WSS of all the seasurface around the worldfrom a Earth gravity model.

- We compute the averageof all the WSS and assumethat this eliminates SSTop,i.e., the average is W0.

- Instead of WSS we alsocan take the average ofSSTop = (W0 - WSS) / γ(Poster Sánchez and Drewes)

SSTop

Conclusions

• SIRGAS defines the unified vertical reference system byellipsoidal heights referring to the GRS80 parameters andnormal heights referring to a global cuasigeoid.

• The level of the cuasigeoid has to be realised in America bythe mean sea level - or another approximation.

• The mean sea level depends on the geographic position.Therefore a kind of average has to be computed.

• The mean sea level also depends on the epoch of definition.Therefore a reference epoch has to be defined.

• Because the (cuasi)geoid varies less than the sea level, onecould include in the averaging of the sea level also somecontinental stations with precise ellipsoidal and normalheights as well as height anomalies (e.g., SIRGAS2000).

IAG PAIGH NIMA

ANNEX VIII


FUTURE ACTIVITIES



fortes


Realización del nivel del Cuasi-geoide


Colombia

EcuadorArgentina

Chile

Bolivia

Perú

Paraguay

∆Wi = ∆Hi

Venezuela

∆ WVen= ∆ HVen

Brasil

∆ WBra= ∆ HBra

Uruguay

∆ WUru= ∆ HUru

HiClásico = H0 + ∆Hi

W0 ≈ H0

Definición de H0


I. Determinación de SSTop por altimetría satelital

Elipsoide

(Cuasi-)geoide

N

SSTop∆HSSTop

Mareógrafo

H0

hHN

ζ

n

HH iSSTop

0∑∆

=

l : extensión total de la costa en América del Sur

∫∆=lH

HSSTop0

Definición de H0


II. Posicionamiento GPS en los mareógrafos de referencia

0Hn

HHhH NiMareog

0iii =∆

=ζ−=∆ ∑

⇒ Posicionamiento GPS repetitivo y registros mareográficos (SIRVEMAS, EVAMARIA)

Problema: El nmm actual no coincide con el nmm en la época de definición (HN ≠ 0)

Solución: Reducción a la época de definición

tdt

dHi ∆

Definición de H0


III. Relación h, HN, ζ (SIRGAS2000)

n

HHHhH iMarco

0Niiii

∑∆=−ζ−=∆

Problema: • La determinación del Cuasi-geoide es muy imprecisa, (dm...m)• Las anomalías gravimétricas se refieren a los sistemas clásicos• Las alturas niveladas parten de mareógrafos, que no coinciden con el (cuasi-)geoide y que no están conectados entre si• Las alturas se han modificado por movimiento verticales, es decir que el posicionamiento GPS y altura nivelada no se refieren a una misma época

HNi (tj) → hi(tk)

Solución:• Utilización de un modelo de cuasi-geoide derivado de las misiones satélitales gravimétricas• Densificación del modelo de cuasi-geoide mediante anomalías locales (iteración)• Corrección de HN

i mediante H0 y consideración del cambio con el tiempo (tk-tj) dH/dt

• Conexión de las redes → discrepancia entre los sistemas clásicos

Corrección de cada sistema nacional con respecto a H0


∫∆=lH

HSSTop0

n

HH iMareog

0∑∆

=

n

HH iMarco

0∑∆

=

Mareógrafos (línea de costa)

Continente

Combinación:

Corrección para cada sistema local:

0SSTopMareog

iIndividual HHH −∆=∆ +

Actividades URGENTES relacionadas con la realización del nivel de referencia vertical en América del Sur


→ Conexión de las redes de nivelación entre países vecinos

→ Nivelación geométrica de las estaciones SIRGAS2000

→ Gravimetría correspondiente

Actividades INMEDIATAS relacionadas con la realización del nivel de referencia vertical en América del Sur


→ Determinación UNIFICADA de un modelo de cuasi-geoide basado en un modelo gravitacional global y densificado mediante anomalías locales (iteración)

→ Determinación de la topografía de la superficie del mar (SSTop) referida al mismo modelo gravitacional global

Conclusiones


Debemos concentrar nuestros esfuerzos en:

• Nivelación geométrica de las estaciones SIRGAS2000

• Conexión de las redes de nivelación entre países vecinos

• Identificación y digitación de todas las líneas de nivelación que conectan las estaciones SIRGAS2000

• Digitación de las redes de nvelación nacionales

• Identificación de los nodos en las redes

• Determinación UNIFICADA del cuasi-geoide

• Determinación de la topografía de la superficie del mar (SSTop) (posicionamiento GPS de los mareógrafos)

IAG PAIGH NIMA

ANNEX IX

STATUTE OF THE SIRGAS PROJECT

(APPROVED BY THE COMMITTEE ON OCTOBER 22, 2002)

Statute of the SIRGAS Project

Geocentric Reference System for the Americas

The SIRGAS Project (Geocentric Reference System for the Americas) by itsobjectives and scope has a Pan-American profile, its execution aims at allnations of the Americas and the Caribbean, and its regulation is contained inthe following articles.

General Objectives

Art. 1. The main objective of the SIRGAS Project is to define, materialize andmaintain the tri-dimensional geocentric reference system for the Americas. Thisobjective includes:

a) Definition of a tri-dimensional geocentric reference system.

b) Establishment and maintenance of a geocentric reference frame (set ofstations with high precision geocentric coordinates [X, Y, Z] and theirvariation with time [Vx, Vy, Vz]).

c) Definition and establishment of a geocentric datum.

d) Definition and materialization of a unique vertical reference system withconsistent physical and geometric heights and the determination of thevariations of the reference frame with respect to time.

Art. 2. The specific objectives of the SIRGAS Project are all those related to themain objective, among them the following can be mentioned:

a) Planning, promotion and coordination of the technical activities requiredto accomplish the main objective.

b) Promotion and dissemination of the advances, results andaccomplishments of the Project, in order to maximize the benefits to thecountries of the region.

c) Permanent participation in the International Association of Geodesy(IAG) and in the Pan-American Institute of Geography and History(PAIGH), in order to exchange up-to-date information and knowledge ontechnical and scientific subjects related to the Project.

d) Encouragement, among the member states, of the homogeneity of thetechnical knowledge involved in the scope of the Project, including thedissemination of the scientific and technological advances whichcontribute to its improvement.

e) Promotion and coordination of all activities that contributes to theaccomplishment of the proposed objectives, including among them theconnection of the pre-existing geodetic systems to SIRGAS.

Members

Art. 3. Only American and Caribbean states can be Members of SIRGAS. Tojoin the Project, it is just necessary to write to the Steering Council (defined inArt. 12) mentioning the interest and the will to actively work towards theaccomplishment of the objectives and to appoint corresponding representatives(according to Art. 7).

Art. 4. The sponsoring institutions of the Project –International Association ofGeodesy (IAG), Pan-American Institute of Geography and History (PAIGH) andU.S. National Imagery and Mapping Agency (NIMA)– are considered Memberswith the same rights and attributions as the member states.

Art. 5. Other states, entities and persons can be observing members, providingthat they do not aim at profits, and they manifest their intention to participate assuch or they are invited by the Project. In any case they must be accepted bythe Executive Committee (defined in Art. 9).

Art. 6. In addition, it is established the category of cooperative state or entityfor those that have required or have been invited by the Project to participate asa contributor in scientific, technical or economic terms. The processing centersthat participate in the Project are considered as such.

Art. 7. The national representatives will be the persons appointed by themember states, through the entities that congregate the scientists andtechnicians in geodesy and related subjects, throughout procedures establishedin each country. The sponsoring entities will appoint their own representatives.

Organization

Art. 8. The following structure units with corresponding roles, defined in thenext articles, are established:

a) Executive Committeeb) Steering Councilc) Working Groupsd) Technical Meetingse) Scientific Council

Art. 9. The Executive Committee is the supreme unit of the SIRGAS Projectand establishes its scientific, technical and administrative directions. Itscomposition and functioning will be governed by the following rules:

a) It will be composed by one representative of each member state and oneof each sponsoring institution. Each member will have one vote and can

appoint a substitute representative who will replace the representative incase he or she is not present.

b) It will ordinarily meet each 4 years. The ordinary meetings will be heldduring the same year as the General Assembly of IAG and, if possible,simultaneously to it.

c) It will be chaired by the president of the Project.

d) The authorities –defined in Art. 12– will have voice but not vote, exceptwhen taking part of the official delegation of his or her country.

e) The observers, cooperative states or entities and the members of theScientific Council will have voice but not vote.

Art. 10. The place of the next ordinary meeting will be decided at each ordinarymeeting, being the place selected from the various cities offered by members ofthe Project. The corresponding agenda will be prepared by the Projectauthorities.

Art. 11. It is established for the resolutions of the Executive Committee:

a) Quorum: it is given by the vote –in presence or by correspondence- oftwo third parts of the members.

b) Vote: assuming fulfilled the quorum as mentioned in a), the proposal thathas the simple majority of votes in favor is accepted.

Art. 12. The Steering Council is composed by the Project authorities, whoare: the president and the vice-president of the Project and the presidents of theworking groups.

Art. 13. The candidates to the position of authorities must be proposed to theExecutive Committee by the entities that sponsor them and must haveconditions of technical capacity internationally recognized in the subjects of theProject.

Art. 14. The states or the sponsoring entities will commit themselves to supporttheir candidates in fulfilling the responsibilities established in this statute.

Art. 15. The president and vice-president of the Project will be elected at theordinary meetings of the Executive Committee, and their term will last 4 years,being eligible to be re-elected for a second term. The presidents of the workinggroups will be appointed by the president of the Project in coordination with theExecutive Committee, and there will be no fixed time for their term.

Art. 16. The presidency of the project and of the working groups will speciallytake into account the opinion of the scientific council when taking decisions andwriting resolutions, considering the recognized professional hierarchy of itscomponents.

Art. 17. The working groups will be established or dissolved by the ExecutiveCommittee according to the Project needs. At the moment of their creation,their general and particular objectives will be established.

Art. 18. The working groups and their objectives will initially be the following:

I – Reference System: to define the geocentric reference system for theAmericas and to coordinate its establishment and maintenance.

II – Geocentric Datum: to coordinate the densification of the geocentricreference frame for the Americas within each member estate of theProject.

III – Vertical Datum: to define a unified height system for the Americas andto coordinate its establishment and maintenance.

Art. 19. The working groups will be composed by their presidents and byexperts who have scientific and technical knowledge and experience in thesubject. The names of such experts can be proposed by members or be invitedby the Project authorities. In any case the final incorporation of an expert to aWorking Group will be performed by the corresponding Working Grouppresident, and ratified by the president and vice-president of the Project.

Art. 20. The presidents of the working groups will permanently keep thepresidency of the Project posted about the activities carried out in the scope ofthe working groups.

Art. 21. The technical meetings will be held whenever scheduled by theExecutive Committee or called by the president of the Project or by thepresidents of the working groups. Their agenda will be prepared by thecorresponding presidents.

Art. 22. The Scientific Council will have the following missions:

a) To advise the presidency of the Project about geodetic techniques,procedures and executions, and eventually about related subjects thatbetter satisfy the imposed requirements.

b) To intervene with working groups and national representatives in order togive directions to their activities, from the scientific point of view, in a wayto better contribute to the accomplishment of the Project objectives.

c) To explain, at the general meetings of the Executive Committee or at theparticular meetings of the working groups, its opinion about the progressof the activities, recommendations that can improve, according to itsunderstanding, the efficiency, and its own analysis about possible actionsteps that would enable to optimize results and to facilitate futureactivities.

Art. 23. The Scientific Council will be governed by the following rules:

a) The appointment of members of the scientific council, among thoseproposed by representatives in the Executive Committee, observers,Project authorities or cooperative entities, will have a permanent nature,and must be accepted by the Executive Committee.

b) The incorporation proposal must be submitted along with a report of theprofessional experience showing the competence and expertisenecessary to occupy the position.

c) Periodically they will inform the presidency of the Project and of theworking groups about the developed activities.

Data policy

Art. 24. The national representatives will deal with the authorities of theirrespective countries to get the corresponding authorizations to have all dataneeded by the Project freely available to it.

Art. 25. The availability mentioned in Art. 24 will be for scientific and/oreducational use only and the sources that provide them will be explicitlymentioned every time they are used.

Art. 26. The use and distribution of the national data utilized during the Projectexecution will be regulated by the particular rules of each member state, beingrequested to the national representatives to arrange their widest availability.

Art. 27. The member states will collaborate with the publication of the respectivemetadata in the webpage of the Project, including the required conditions fortheir use.

Art. 28. The computation centers will facilitate to the member states and to thecooperative entities the access to data, to computation procedures, to theirresults and to all available information related to the Project.

Language

Art. 29. The official languages of the Project will be Spanish, Portuguese andEnglish. In any case, the Spanish version of this statute will prevail.

Webpage

Art. 30. The Project will have a webpage, whose edition will be under thepresident´s responsibility, with the collaboration of the vice-president. Thepresidents of the working groups will have the obligation of supplying theinformation to be published. The participant states, the observing members andthe sponsoring and cooperative entities will also contribute with relevant news

and periodic information. All Project reports will be released through thewebpage.

Art. 31. The page contents should be constantly updated, being recommendeda complete review at least two times a year.

Art. 32 (transitory). The present statute will take effect at the moment of itsapproval by the Executive Committee.

IAG PAIGH NIMA

ANNEX X

LIST OF ATTENDEES TO THE SANTIAGO MEETING

IAG PAIGH NIMA

NAME COUNTRY E-MAIL1 Alfonso Tierra Ecuador [email protected] CAP. Rafael Delgado Ecuador [email protected] Carlos Alberto Corrêa e Castro Jr Brazil [email protected] Claudio Brunini Argentina [email protected] Daniel Del Cogliano Argentina [email protected] Denizar Blitzkow Brazil [email protected] Eduardo Lauría Argentina [email protected] Fabian Barbato Uruguay [email protected] Felipe Eduardo Vásquez Moya Bolivia [email protected]

10 Hayo Hase Chile [email protected] Hector Parra Chile [email protected] Hermann Drewes Germany [email protected] J. Derek Fairhead UK [email protected] Johannes Ihde Germany [email protected] Jorge Velásquez Ecuador [email protected] Jose Napoleón Hernández Venezuela [email protected] Juan Carlos Baez Soto Chile [email protected] Jürgen Klotz Germany [email protected] Klaus Kaniuth Germany [email protected] Laura Sánchez Colombia [email protected] Lautaro Díaz Chile [email protected] Lorenzo Centurion Carmona Paraguay [email protected] Luiz Paulo Souto Fortes Brazil [email protected] María Cristina Pacino Argentina [email protected] Maria Paula Natali Argentina [email protected] MAY. Alvaro Hermosilla Chile [email protected] Melvin Hoyer Venezuela [email protected] Muneendra Kumar USA [email protected] Roberto Teixeira Luz Brazil [email protected] Silvio R. Correia de Freitas Brazil [email protected] Sonia Costa Brazil [email protected] TCL. Oscar Cifuentes Chile [email protected] TCL. Rodrigo Barriga Chile [email protected] TCL. Rodrigo Maturana Chile [email protected] Washington Vinuez Ecuador wasvin@hotmail36 Wolfgang Schluter Germany [email protected] Wolfgang Seemueller Germany [email protected]

IAG PAIGH NIMA

ANNEX XI

PICTURES OF THE MEETING



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