Table 1.--Format of gravity data
[ft, feet; g/cc, grams/cubic-centimeter; mGal, milligal]
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Column Format Description
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1-8 A8 Station name
10-11 F2.0 Latitude, in degrees
12-15 F4.2 Latitude, in minutes to 0.01 minute
17-19 F3.0 Longitude, in degrees
20-23 F4.2 Longitude, in minutes to 0.01 minute
24-29 F6.1 Elevation, in ft to 0.1 ft
30-36 F7.2 Observed gravity, in mGal to 0.01 mGal, without leading 9
37-40 A4 Four character accuracy code
41-46 F6.2 Free-air anomaly, in mGal to 0.01 mGal
47-52 F6.2 Simple Bouguer anomaly, in mGal to 0.01 mGal
53-57 F5.2 Inner-zone terrain correction, in mGal to 0.01 mGal
58-62 F5.2 Total terrain correction, in mGal to 0.01 mGal
63 A1 Terrain correction code denoting extent of
inner-zone terrain correction and system, upper
case denotes Hayford-Bowie system of zones,
lower case denotes Hammer system of zones.
Z, computer calculated from 0.0-0.59 km
64-69 F6.2 Complete Bouguer anomaly reduced for a density
of 2.67 g/cc, in mGal to 0.01 mGal
70-75 F6.2 Isostatic gravity anomaly reduced for a density
of 2.67 g/cc, in mGal to 0.01 mGal
76-80 A4 Comment ______________________________________________________________________

Table 2.--Explanation of 4-digit accuracy code
[alt, altimetry; blk, black; brn, brown; elev., elevation;
NGS, National Geodetic Survey; NMD, National Mapping Division;
PG, photogrammetry; USGS, U. S. Geological Survey;
VABM, vertical angle bench mark]
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General elevation and location code--First digit
Code Explanation
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A Altimetry, good control
B On USGS or NGS level-line bench mark
C Contour line interpolation
D Destroyed or not found reference mark
E Near non-USGS level-line bench mark
F Map elev., blk or field checked
G Map elev., brn or not field checked
H Near vertical angle bench mark
I Other special source
K Photogrammetry by other than USGS NMD
M On non-USGS level-line bench mark
N Near USGS or NGS level-line bench mark
P On or near surveyed mark
Q River gradient interpolation
R Lake elev. by leveling
S Sea level elev.
T Photogrammetry by USGS NMD
U Unknown elev. source
V On vertical angle bench mark
W Map elev., blue
X On or near boundary marker
Y Altimetry, poor control
Z Special source