INTRODUCTION TO UTM COORDINATES AND MAP

DATUMS

UTM COORDINATES

ZONE CENTRALMERIDIAN = 500,000 m

300,000 700,000500,000

108 102105105

TRANSVERSE MERCATOR

UTM ZONES UNITED STATES

NM

UTM CARTISIAN COORDINATES

USGS MAPS AND UTM

COORDINATE SYSTEMS

• NAD 27 = North American Datum, 1927

• NAV 29 = North American Vertical, 1929

• NAD 83 = North American Datum, 1983

• WGS 84 = World Geodetic System 1984

• (ALL GPS)

• CORPSCON – CONVERSION PROGRAM

• INTRODUCTION TO MAGNETIC METHODS

– Earth’s Magnetic Field– Rock Magnetism– Geologic Models Magnetic Anomaly Sources– Planning a Survey– Examples

REFERENCE:Sheldon Breiner, Applications Manual for Portable Magnetometers

www.georentals.co.uk/ampm-opt.pdf

TOTAL FIELD MEASUREMENTS

EARTH’S DIPOLE FIELD

MAGNETIC ELEMENTS

H = F cos I Z = F sin I = H tan IX = cos D Y = H sin D

X² + Y² = H² X² + Y² + Z² = F²

F = Total Field IntensityI = Inclination

D = DeclinationH = Horizontal Component

X = North ComponentY = East Component

Z = Vertical Component

East

North

TOTAL INTENSITY

25

70

X 1000 nTeslas

50

50

GEOMAGNETIC INCLINATION

60N

80N

0

80S60S

GEOMAGNETIC INCLINATION DEGREES OF ARC FROM HORIZONTAL

CHANGES IN DECLINATION AND INCLINATION AT LONDON SINCE 1540

SECULAR VARIATIONS

2010

Declination

Incl

inat

ion

SOLAR DIURNAL VARIATIONSMID NORTHERN AND MID SOUTHERN LATITUDES

50 nT

EQUATORIAL LATITUDES

MICRO PULSATIONS

10 nT

10 minutes

TYPICAL MAGNETIC STORM

50 nT

1 day

CORRECTING FOR TIME VARYING FIELDS

• F = f(x,y,z,t)– x = Easting (Longitude)– y = Northing (Latitude)– z = Elevation (very small effect)– t = time

• FB = Field at Base Station (time dependent)

• FR = Field at Rover (space/time dependent)

• FC = Time Correct Field at Rover = FB – FR

• GEOREF = Geomagnetic Reference Correction

AVERAGE MAGNETIC SUSCEPTIBILITIES

BASIC IGENOUS

ACID IGNEOUS

METAMORPHICSEDIMENTARY

Mag

netic

Sus

cept

ibili

ty x

106

(c.g

.s.)

MEASURED SUSCEPTIBILITIES OF ROCK MATERIALS

Material K x 106 cgs At H, OeMagnetite 300,000-800,000 0.6

Pyrrhotite 125,000 0.5

Ilmenite 135,000 1.0

Franklinite 36,000

Granite 28-2700 1.0

Diorite 46.8 1.0

Gabbro 68-2370 1.0

Basalt 680 1.0

Sandstone 16 1.0

INDUCED VS REMANENT MAGNETIZATION

• Induced Magnetization– Polarization in direction of Earth’s Field

• Remanent Magnetization– Thermoremanent (Curie Temperature)– Detrital (Depositional)– Chemical

GEOLOGICAL MODEL REPRESENTATIONS OF COMMON MAGNETIC ANOMALY SOURCES

Dipoles vs. Monopoles vs. Arrays of Poles

ANOMALIES FOR GEOLOGICAL BODIES AT VARIOUS ORIENTATIONS AND FIELD INCLINATIONS

↓ F F F→F→F

T N-ST E-WT N-ST E-W

12345

TOTAL INTENSITY INDUCED DIPOLE SIGNATURESAT VARIOUS INCLINATIONS OF THE FIELD

Induced dipoleVertical Field

(North or South Poles)

Induced dipole(Inclination 60º)

Induced dipoleEquatorial Field(Inclination 0º)

REMANENT DIPOLE SIGNATURESMOMENT NOT PARALLEL TO INDUCING FIELD

EFFECT OF DEPTH ON ANOMALY WIDTH

The amplitude of the anomaly is maintained constantBy adjusting the size of the anomalous body.

DEPTH/AMPLITUDE BEHAVIOR OF DIPOLE

ANOMALIES

M

8M M

Note: Same Amplitude butChange in width

F

DISTANCE

nT

500

100

1

10

20010 Ft

1 ton iron

ANOMALIES OF COMMON OBJECTS

• OBJECT Ft/nT Ft/nT• Automobile (1 ton) 30/40 100/1• Ship (1000 ton) 100/300-700 1000/1• Aircraft (light) 20/10-30 50/1• Pipeline (12”) 25/50-200 50/12-50• Wellhead 50/200-500 500/2-5• Fenceline 10/15 25/1-2• Rifle 5/10-50 10/ 2-10 • Revolver 5/10-20 10/1-2

TYPICAL MAGNETIC ANOMALIES OF COMMON ARCHAEOLOGICAL FEATURES

Kiln-baked brick wallSandstone wall in

more magnetic soil

Shallow grave or pathway

Humus-rich siteof habitation

Shallow tomb Deeply buried tomb Bricks in disarray Fire pit with bricksIn original position

PLANNING A SURVEY

• SIZE OF TARGET

• AERIAL EXTENT OF SEARCH

• GROUND OR AIRBORNE

• RESOLUTION OF SURVEY

• FIELD METHODS

• PITFALLS

• EXAMPLES

TYPICAL SEQUENCES OF TRAVERSES DURING SEARCH PROCEDURES

Secondary Traverse

Prim

ary

Tra

vers

e

Prim

ary

Tra

vers

e

Prim

ary

Tra

vers

e

Fin

al T

rave

rse

Object location

Total magnetic field contours(not known during search)

ESTIMATION OF DEPTH TO TOP OF ANOMALOUS BODIES USING MAXIMUM SLOPE

52490 nT

52195 nT

52280 nT

Contour Interval 5 nT

GNTN

Maximum slope 5 m

F

DISTANCE

nT

500

100

1

10

20010 Ft

1 ton iron

SOLUTION FOR BILLSCRATER

MAGNETIC EFFECT OF LATERAL SUSCEPTIBILITY CHANGE VS STRUCTURE

HIGH RESOLUTION AIRBORNE MAGNETIC MAP OF THE SAGE 2010 FIELD AREA

SAGE 2005SEISMIC PROFILE

SAGE 2005MT PROFILE

SAGE 2010ARCH SITE