AUTHOR: Jenn Willems
Converts coordinates from one datum, projection, and/or unit to another. C_TRANSINIT must be called pror to running this function.
C_TRANS will replace C_PROJ as a support to do the conversions.
C_PROJ used GCTP to convert coordinates from one projection and/or unit to another. The functionality was needed to convert coordinates from one datum to another. The algorithms used to do the datum conversions are from the function DATUMCHG wich was written by Dan Steinwand. The output was tested by running the same values through NIMA's DTCC4.
1. The current functionality of C_PROJ must still exist. 2. Need capability to convert from UTM to another projection with any spheroid. 3. Must be able to convert from one datum to another. 4. The datum needs to be represented in the ddr, while still being able to use old ddrs. 5. NADCON should be used for conversion from NAD27 to NAD83. The Moldensky equations can be used for all other conversions. 6. If NADCON errors when a point is out of its range, the Molodensky equations should be used to convert the point.
1. The datum value in the ddr must represent a datum value. The datum value cannot be assumed by the software. 2. The spheroids the datum use must be supported spheroids by GCTPC.
TRANS: Swap x and y (and negate y) for SOM Convert the coordinates to geographic using GCTP:
- INPROJ
- Input: Input projection code.
- INUNIT
- Input: Input projection unit code.
- OUTPROJ
- Input: Output projection code.
- OUTUNIT
- Input: Output projection unit code.
- INX
- Input: Input X projection coordinate.
- INY
- Input: Input Y projection coordinate.
- OUTX
- Output: Output X projection coordinate.
- OUTY
- Output: Output Y projection coordinate.
Error returned from coordinate conversion Error returned from datum conversion Datum flag does not represent a conversion Could not convert from Degrees to DMS Could not convert to Degrees Error returned from unit factor Error returned from inverse transformation Error returned from forward transformation
1. Run the same tests used to test the algorithms and verify results. 2. Validate that all projection conversions are the same as with c_proj. 3. Check to see that UTM can now be converted to another projection with any spheroid and back. 4. Validate that converting from one datum to another and back yields the same data. 5. Verify that using trancoord-nad, and converting from nad27 to nad83 yeilds the same results. 6. Check combinations of non-nad datums to nad datums. 7. Tested that values outside NADCON's range were converted properly using molodensky transformations.