Input Files

Gravity Station File

LaserTC requires several input files to run. First, a file containing the gravity observations is required. Then, for each gravity observation supplied, an elevation data file must be supplied separately; the maximum number of files required for execution is therefore N+1, where N is the number of gravity observations supplied. The gravity file contains pointers to the elevation data sets that accompany each gravity observation. Each gravity observation and associated elevation data file are on a single record of the input file. Each record of the input file must contain the following information in a comma- or space-delimited list:
Some example gravity station files are shown below:

Example 1a.

This is an example of the simplest sort of input file. There are but two gravity stations, and both the observed gravity value and the location of the gravity station are set to 0. Because the observed gravity value is never actually used by LaserTC, its value is arbitrary. However, the coordinates of the gravity station supplied imply that the associated elevation data (supplied on the files mine.dat and mall.dat, respectively) must be in different coordinate frames, each having the gravity station location as its origin. 

Getchell mine.dat  0 0 0 0
MallData mall.dat  0 0 0 0

Example 1b.

This example is the same as example 1a, except that the input file provided should only be used when the -1 option is used when executing LaserTC. The -1 option instructs LaserTC to use the first coordinate triple from the elevation data file as the coordinate of the gravity station. Hence, one does not need to supply the gravity station coordinates on the file: only the Station Identifier, the elevation file name, and the observed gravity value are needed.
Note that if one uses the -1 option, one may still provide station coordinates on the gravity input file, but such coordinates will be ignored. 

Getchell mine.dat  0
MallData mall.dat  0
Note that one may use the same elevation file for multiple gravity observations. In such cases, it is most efficient to group those gravity observations sharing the same elevation file together, as the elevation file is only re-read when it changes. Some examples are provided below.

Example 2a.


g001  mine.xyz     979794.62   866186.19  2364123.25  5583.8
g002  mine.xyz     979792.25   865930.88  2364108.50  5621.6
g003  mine.xyz     979788.25   865671.81  2364090.50  5683.8
g004  mine.xyz     979786.06   865420.25  2364075.75  5722.6
g005  mine.xyz     979784.25   865161.19  2364061.00  5751.2
g006  mine.xyz     979783.62   864894.56  2364046.25  5760.6
g007  mine.xyz     979782.88   864631.75  2364034.75  5766.3
g008  mine.xyz     979782.69   864372.56  2364025.00  5771.2
g009  mine.xyz     979785.06   864113.31  2364020.00  5736.9
g010  mine.xyz     979786.50   863858.06  2364002.00  5715.1
g011  mine.xyz     979784.75   863598.56  2364013.50  5740.0
g012  mine.xyz     979781.94   863343.06  2364011.75  5786.2
g013  mine.xyz     979778.75   863091.31  2364006.75  5842.3
g014  mine.xyz     979774.19   862835.81  2364003.50  5914.7
g015  mine.xyz     979769.62   862591.56  2364002.00  5988.8
g016  mine.xyz     979767.06   862336.06  2364000.25  6033.1
g017  mine.xyz     979768.69   862069.44  2363988.75  6013.3
g018  mine.xyz     979759.56   860975.38  2364766.50  6157.8
g019  mine.xyz     979761.81   861234.69  2364766.50  6124.4
g020  mine.xyz     979762.69   861493.94  2364766.50  6109.3
g021  mine.xyz     979763.75   861753.25  2364768.25  6092.5
g022  mine.xyz     979764.75   862008.69  2364774.75  6073.0
g023  mine.xyz     979766.75   862256.62  2364783.00  6039.5
In the above example, the same elevation data file ("mine.xyz") is used for all the gravity stations to be terrain-corrected. This file is read only once, rather than each time a station is to be corrected. This results in considerable time-savings compared to having to read and process the elevation data file for each gravity station.

Example 2b.


g113  mine.xyz     979803.75   868578.25  2359366.25  5399.7
g114  mine.xyz     979805.38   868822.19  2359387.75  5373.2
g115  mine.xyz     979805.38   869000.25  2359540.25  5370.8
g116  g116.elv     979806.25   869175.06  2359665.00  5355.8
g117  mine.xyz     979809.12   869596.38  2359399.25  5311.2
g118  g118.elv     979811.12   869818.38  2359384.50  5284.2
g119  mine.xyz     979813.25   870074.12  2359374.50  5253.4
g120  mine.xyz     979813.38   870341.38  2360076.75  5256.1
g121  mine.xyz     979813.12   870518.12  2360073.50  5263.6
g122  mine.xyz     979811.75   870777.69  2360058.75  5288.6
g123  mine.xyz     979812.50   871037.00  2360060.50  5277.3
g124  mine.xyz     979813.56   871292.56  2360062.00  5261.3
g125  g125.elv     979789.56   865875.19  2357677.75  5594.8
g126  mine.xyz     979790.75   865873.44  2357298.75  5568.7
g127  mine.xyz     979791.25   865868.69  2357118.25  5556.3
In Example 2b, the file "mine.xyz" is used as the source of the elevation data for most of the gravity stations to be terrain-corrected. However, some stations (g116, g118, and g125) used different files for the source of their elevation data. While this input gravity file will work properly, it would be considerably more efficient to group all those stations having the file "mine.xyz" as their elevation source files sequentially.

Elevation Data Files

Each record of the gravity station dat file points to an elevation data file. This file is a very simple file consisting simply of the coordinates of each elevation sample, one sample coordinate triplet per record. That is, each record of the elevation data file is composed simply of the three values coorsponding to the x,y,elevation of each elevation sample. The values may be either comma-delimited, space-delimited or tab-delimited.

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