INTRODUCTION TO UTM
COORDINATES AND MAP
DATUMS
UTM COORDINATES
300,000
500,000
700,000
105
108
105
102
ZONE CENTRAL
MERIDIAN = 500,000 m
TRANSVERSE MERCATOR
UTM ZONES UNITED STATES
NM
UTM CARTISIAN COORDINATES
USGS MAPS AND UTM
COORDINATE SYSTEMS
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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
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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
North
F = Total Field Intensity
I = Inclination
D = Declination
H = Horizontal Component
X = North Component
Y = East Component
Z = Vertical Component
East
H = F cos I Z = F sin I = H tan I
X = cos D Y = H sin D
X² + Y² = H² X² + Y² + Z² = F²
TOTAL INTENSITY
50
25
50
70
X 1000 nTeslas
GEOMAGNETIC INCLINATION
80N
60N
0
60S
80S
GEOMAGNETIC INCLINATION DEGREES OF ARC FROM HORIZONTAL
CHANGES IN DECLINATION AND INCLINATION AT
LONDON SINCE 1540
SECULAR VARIATIONS
Declination
2010
SOLAR DIURNAL VARIATIONS
MID NORTHERN AND MID SOUTHERN LATITUDES
EQUATORIAL LATITUDES
50 nT
MICRO PULSATIONS
10 minutes
10 nT
TYPICAL MAGNETIC STORM
50 nT
1 day
CORRECTING FOR TIME VARYING FIELDS
• F = f(x,y,z,t)
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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
Magnetic Susceptibility x 106 (c.g.s.)
AVERAGE MAGNETIC
SUSCEPTIBILITIES
BASIC IGENOUS
ACID IGNEOUS
METAMORPHIC
SEDIMENTARY
MEASURED SUSCEPTIBILITIES OF ROCK
MATERIALS
Material
K x 106 cgs At H, Oe
Magnetite
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
1
2
3
4
5
↓ F
F
F
→F
→F
T N-S
T E-W
T N-S
T E-W
TOTAL INTENSITY INDUCED DIPOLE SIGNATURES
AT VARIOUS INCLINATIONS OF THE FIELD
Induced dipole
Vertical Field
(North or South Poles)
Induced dipole
(Inclination 60º)
Induced dipole
Equatorial Field
(Inclination 0º)
REMANENT DIPOLE SIGNATURES
MOMENT NOT PARALLEL TO INDUCING FIELD
EFFECT OF DEPTH ON
ANOMALY WIDTH
The amplitude of the anomaly is maintained constant
By adjusting the size of the anomalous body.
DEPTH/AMPLITUDE BEHAVIOR OF DIPOLE
ANOMALIES
Note: Same Amplitude but
Change in width
M
8M
M
500
F
100
nT
10
1
10
DISTANCE
200
Ft
ANOMALIES OF COMMON OBJECTS
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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 wall
Shallow tomb
Sandstone wall in
more magnetic soil
Deeply buried tomb
Shallow grave
or pathway
Bricks in disarray
Humus-rich site
of habitation
Fire pit with bricks
In original position
PLANNING A SURVEY
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SIZE OF TARGET
AERIAL EXTENT OF SEARCH
GROUND OR AIRBORNE
RESOLUTION OF SURVEY
FIELD METHODS
PITFALLS
EXAMPLES
TYPICAL SEQUENCES OF TRAVERSES
DURING SEARCH PROCEDURES
Object
location
Total magnetic field contours
(not known during search)
Primary Traverse
Primary Traverse
Final Traverse
Primary Traverse
Secondary Traverse
ESTIMATION OF DEPTH TO TOP OF
ANOMALOUS BODIES USING MAXIMUM SLOPE
Maximum slope 5 m
52195 nT
52490 nT
TN
GN
52280 nT
Contour Interval 5 nT
500
F
SOLUTION FOR BILLS
CRATER
100
nT
10
1
10
DISTANCE
200
Ft
MAGNETIC EFFECT OF LATERAL
SUSCEPTIBILITY CHANGE VS STRUCTURE
HIGH RESOLUTION AIRBORNE MAGNETIC
MAP OF THE SAGE 2010 FIELD AREA
SAGE 2005
MT PROFILE
SAGE 2010
ARCH SITE
SAGE 2005
SEISMIC PROFILE