GETRA
Perform geodetic coordinate transformations
GETRA transforms coordinates between the principal coordinate systems used in geodetic work. It can, for example, convert control-point coordinates from different source systems into one common system or transform global coordinates into a local Cartesian system for plotting.
GETRA can transform the following coordinate types:
- Geocentric coordinates
- Geographic coordinates
- Gauss-Krüger coordinates
- Universal Transverse Mercator coordinates (UTM)
- Local Cartesian coordinates
GETRA reads coordinates from an input file, performs one transformation, and writes the result to an output file. A conversion from Gauss-Krüger coordinates to a local tangential Cartesian system therefore requires three runs:
- Gauss-Krüger to geographic coordinates
- Geographic to geocentric coordinates
- Geocentric to local Cartesian coordinates
For a transformation into a local system, define the local origin in the global geocentric system. Choose a point near the center of the area and use convenient rounded coordinates. Before the second transformation above, place this origin first in the input file. GETRA stores it in GEOCENT.REF for the reverse transformation.
GETRA provides eight predefined reference ellipsoids and supports up to 20 definitions in ELLI.PAR. The program creates this file in the BINGO directory on its first run. Edit it to add an ellipsoid or change its parameters.
GETRA does not perform a datum transformation between different reference ellipsoids. Use the same ellipsoid for every transformation in a data set.
Input and output are ASCII text files. Input records use free format. Each record must contain all required values on one line:
Number, X, Y and Z
If a value is missing, GETRA continues reading from the next line and the records will be interpreted incorrectly.
In files with geographic coordinates, each line must include:
Number, λ, φ, and Z
Longitude and latitude each consist of three values: degrees, minutes, and seconds.
GETRA is dialogue-driven and must be started from BINGO Manager.
Dialogue examples and data file contents
Input of geographic coordinates
File GEOGR.DAT:
113 5. 17. 5.4359 43. 35. 21.1126 253.000
114 5. 9. 41.0407 43. 36. 9.9526 88.000
115 5. 12. 43.7820 43. 41. 16.4945 227.000
116 5. 22. 58.5200 43. 39. 55.5765 352.000
117 5. 29. 22.3114 43. 38. 24.7371 227.000
127 5. 23. 7.8379 43. 43. 39.3593 163.000
128 5. 15. 48.4626 43. 44. 14.2308 131.000
129 5. 18. 51.3738 43. 48. 37.1644 511.000
130 5. 24. 47.9471 43. 48. 56.0394 855.000
143 5. 23. 29.1309 43. 58. 31.5611 780.000
144 5. 27. 53.7865 43. 57. 39.4220 841.000
145 5. 38. 46.7600 43. 55. 0.5737 627.000
Output of UTM coordinates
File UTM.DAT:
113 31684455.001 4828475.000 253.000
114 31674450.000 4829715.001 88.000
115 31678295.000 4839280.001 227.000
116 31692130.001 4837165.000 352.000
117 31700810.001 4834615.001 227.000
127 31692140.001 4844075.001 163.000
128 31682280.001 4844875.001 131.000
129 31686145.000 4853100.001 511.000
130 31694095.001 4853910.001 855.000
143 31691820.001 4871615.001 780.000
144 31697765.000 4870180.001 841.000
145 31712475.001 4865730.001 627.000
Dialogue example
The following example shows an interactive GETRA session.
PROGRAM GETRA VERS. 3.0 / 01.98
TRANFORMATIONS OF COORDINATES IN MAIN GEODETIC PROBLEMS
------------------------------------------------------------------------
AVAILABLE REFERENCE ELLIPSOIDS
------------------------------ NO. ELLIPSOID
1 Bessel
2 Hayford - International Ellipsoid
3 Krassowski
4 I.U.G.G.- Geodetic Reference System 1980
5 Clarke 1866 (North American Datum)
6 Clarke 1878/80
7 WGS 72 - World Geodetic System 1972
8 WGS 84 - World Geodetic System 1984 (GPS)
Ellipsoid number [2] .......................................... > 6
ELLIPSOID : Clarke 1878/80
AE = 6378249.200
FX = 293.4660208
SUPPORTED COORDINATE SYSTEMS
----------------------------
GK = Gauss - Krueger : East,North,Height
UTM = Universal Transversal Mercator : East,North,Height
GCENT = Geocentric Coordinates : X, Y, Z
GEOGR = Geographic Coordinates : Longi,Lati,Height
LOCAL = Local Cartesian Coordinates : XL, YL, ZL
Mode Function Mode Function
1 : GCENT to GEOGR 2 : GEOGR to GCENT
3 : GK to GEOGR 4 : GEOGR to GK
5 : UTM to GEOGR 6 : GEOGR to UTM
7 : GCENT to LOCAL 8 : LOCAL to GCENT
Transformation mode ........................................... > 6
Transformation to the nearest central meridian (Y/N) [Y] ....... > n
Code number of the central meridian or -99 to use nearest
central meridian ............................................... > 31
Name of file with input data or /A to abort [GEOGR.DAT] ......... >
Name of file for output data or /A to abort [UTM.DAT] ........... >
Input file = GEOGR.DAT, output file = UTM.DAT
Transformation from GEOGRAPHIC to UTM
No. of transformed points: 12
End GETRA
Ellipsoid parameter file
File ELLI.PAR:
C Ellipsoid Parameters:
C
C I : index number (max 20)
C AE : semimajor axis [metres]
C FX : flattening = 1 / FX
C NAME : name of ellipsoid (max 42 char)
C
C I AE FX NAME
C-- ------------ ------------ ------------------------------------------
1 6377397.155 299.1528129 Bessel
2 6378388.000 297.0000000 Hayford - International Ellipsoid
3 6378245.000 298.3000000 Krassowski
4 6378137.000 298.2572221 I.U.G.G.- Geodetic Reference System 1980
5 6378206.400 294.9786980 Clarke 1866 (North American Datum)
6 6378249.200 293.4660208 Clarke 1878/80
7 6378135.000 298.2600000 WGS 72 - World Geodetic System 1972
8 6378137.000 298.2572221 WGS 84 - World Geodetic System 1984 (GPS)