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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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UTM COORDINATES 300,000 500,000 700,000 105 108 105 102 ZONECENTRAL MERIDIAN = 500,000 m
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
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 1540SECULAR VARIATIONS Declination 2010 Inclination
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) • 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 Magnetic Susceptibility x 106 (c.g.s.) ACID IGNEOUS METAMORPHIC SEDIMENTARY
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
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 SIGNATURESAT 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 SIGNATURESMOMENT 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
F 500 1 ton iron 100 nT 10 1 10 200 Ft DISTANCE
ANOMALIES OF COMMON OBJECTS • OBJECTFt/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 Shallow grave or pathway Humus-rich site of habitation Kiln-baked brick wall Sandstone wall in more magnetic soil Bricks in disarray Fire pit with bricks In original position Shallow tomb Deeply buried tomb
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 Object location Total magnetic field contours (not known during search) Secondary Traverse Primary Traverse Primary Traverse Primary Traverse Final Traverse
ESTIMATION OF DEPTH TO TOP OF ANOMALOUS BODIES USING MAXIMUM SLOPE
Maximumslope5 m 52195 nT 52490 nT TN GN 52280 nT Contour Interval 5 nT
F 500 SOLUTIONFORBILLS CRATER 1 ton iron 100 nT 10 1 10 200 Ft DISTANCE
MAGNETIC EFFECT OF LATERAL SUSCEPTIBILITY CHANGE VS STRUCTURE
HIGH RESOLUTION AIRBORNE MAGNETIC MAP OF THE SAGE 2010 FIELD AREA SAGE 2010 ARCH SITE SAGE 2005 MT PROFILE SAGE 2005 SEISMIC PROFILE