INTRODUCTION TO UTM COORDINATES AND MAP DATUMS

UTM COORDINATES ZONE CENTRAL MERIDIAN = 500,000 m 300, , ,

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

TOTAL FIELD MEASUREMENTS

EARTH’S DIPOLE FIELD

MAGNETIC ELEMENTS 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 F = Total Field Intensity I = Inclination D = Declination H = Horizontal Component X = North Component Y = East Component Z = Vertical Component East North

TOTAL INTENSITY X 1000 nTeslas 50

GEOMAGNETIC INCLINATION 60N 80N 0 80S 60S GEOMAGNETIC INCLINATION DEGREES OF ARC FROM HORIZONTAL

CHANGES IN DECLINATION AND INCLINATION AT LONDON SINCE 1540 SECULAR VARIATIONS 2010 Declination Inclination

SOLAR DIURNAL VARIATIONS MID 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 F B = Field at Base Station (time dependent) F R = Field at Rover (space/time dependent) F C = Time Correct Field at Rover = F B – F R GEOREF = Geomagnetic Reference Correction

AVERAGE MAGNETIC SUSCEPTIBILITIES BASIC IGENOUS ACID IGNEOUS METAMORPHIC SEDIMENTARY Magnetic Susceptibility x 10 6 (c.g.s.)

MEASURED SUSCEPTIBILITIES OF ROCK MATERIALS MaterialK x 10 6 cgsAt H, Oe Magnetite300, , Pyrrhotite125, Ilmenite135, Franklinite36,000 Granite Diorite Gabbro Basalt Sandstone161.0

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 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 60 º) Induced dipole Equatorial Field (Inclination 0 º)

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 M 8MM Note: Same Amplitude but Change in width

F DISTANCE nT Ft 1 ton iron

ANOMALIES OF COMMON OBJECTS OBJECT Ft/nT Ft/nT Automobile (1 ton) 30/40 100/1 Ship (1000 ton) 100/ /1 Aircraft (light) 20/ /1 Pipeline (12”) 25/ /12-50 Wellhead 50/ /2-5 Fenceline 10/15 25/1-2 Rifle 5/ / 2-10 Revolver 5/ /1-2

TYPICAL MAGNETIC ANOMALIES OF COMMON ARCHAEOLOGICAL FEATURES Kiln-baked brick wall Sandstone wall in more magnetic soil Shallow grave or pathway Humus-rich site of habitation Shallow tomb Deeply buried tomb Bricks in disarray Fire pit with bricks In 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 Primary Traverse Final Traverse Object location Total magnetic field contours (not known during search)

ESTIMATION OF DEPTH TO TOP OF ANOMALOUS BODIES USING MAXIMUM SLOPE

52490 nT nT nT Contour Interval 5 nT GNTN Maximum slope 5 m

F DISTANCE nT Ft 1 ton iron SOLUTION FOR BILLS CRATER

MAGNETIC EFFECT OF LATERAL SUSCEPTIBILITY CHANGE VS STRUCTURE

HIGH RESOLUTION AIRBORNE MAGNETIC MAP OF THE SAGE 2010 FIELD AREA SAGE 2005 SEISMIC PROFILE SAGE 2005 MT PROFILE SAGE 2010 ARCH SITE