U.S. Geological Survey
Medina and Uvalde Counties,Texas, High-Resolution Aeromagnetic Survey  
Flown: March 2001 - April 2001

0.25 mile east/west traverse lines
2.5 mile north/south tie lines
500ft drape elevation

Geosoft Database provided in Geosoft Oasis Montaj Version 5.0 
GEOSOFT GDB and ASCII (XYZ) file fields defined as follows:

line,NORMAL,5,1	reflights/extensions terminate in 1 or 2 (i.e., Line 21 is a reflight 
			of Line 20); tie lines start at 5000
longitude,NORMAL,11,4	  WGS84
latitude,NORMAL,9,4	  WGS84
x,NORMAL,9,2		  WGS84 UTM ZONE 14, CENTRAL MERIDIAN -99 (261)
y,NORMAL,10,2		  WGS84 UTM ZONE 14, CENTRAL MERIDIAN -99 (261)
fiducial,NORMAL,12,1
gpstime,NORMAL,11,1	  TIME IN SECONDS FROM START OF GPS WEEK
radaralt,NORMAL,9,2	  UNITS - METERS
galtdiff,NORMAL,10,4	  PLATFORM ALTITUDE UNITS - METERS
basemag,NORMAL,10,4	  BASE STATION MAGNETICS
rawmag,NORMAL,10,4	  RAW MAGNETICS, NO CORRECTIONS
compmag,NORMAL,10,4	  COMPENSATED MAGNETICS
magdc,NORMAL,10,4	  DIURNAL CORRECTED COMPENSATED MAGNETICS
magdclhigrf,NORMAL,12,4	  CORRECTIONS: DIURNAL, LAG, HEADING, IGRF
finallevel,NORMAL,10,4	  FINAL MICRO LEVELED MAGNETICS
igrf,NORMAL,10,4
 

Base constant added after diurnal correction and IGRF correction = 48,400

Survey contractor:
SPECTRA EXPLORATION GEOSCIENCE CORP.
Suite 2610, 520-5th Avenue SW
Calgary, Alberta, Canada  T2P 3R7
phone  403-777-9280
fax 403-777-9289