Error with reprojection from REUNION.Reunion/TM/03 to RGR92.UTM-40S

[mambrosy]

Hi,

I have noticed an issue when I reproject data from old system "REUNION.Reunion/TM/03" to the new system "RGR92.UTM-40S".

I have compared results beetween the french official and valuable reprojection software "Circé" from IGN and CSMAP. I join you the TEST.DAT file and the result file from the "./CS_Test -t4 -d../Dictionaries" command.

You'll see a bad interval of approximatively 16 meters on X and 5 meters on Y.

Regards.

[mambrosy]

TEST.DAT and result.txt

[Norm Olsen]

It appears that CS-MAP has been using an older definition of the transformation from Reunion 1947, to Reunion 1992. That transformation was EPSG Transformation Code 15751. A newer transformation, EPSG Transformation Code 1926 has been implemented as the geodetic transformation from Reunion47_to_Reunion92. This transformation produces results which are within 20 centimeters of the results given in the data submitted with this ticket.

A new coordinate system, Reunion47.Reunion/TM has been defined which references a new datum definition, Reunion47, which therefore forces the use of the newer datum transformation. This will produce the indicated results. Why the results are different by as much as 20 centimeters I cannot tell. Perhaps there is a precision difference in the parameters specifications? I do not have a copy of the references application, circe, so I cannot investigate any further.

[Norm Olsen]

I forgot to mention, the submission which corrected this defect produced revision 2695.

[Norm Olsen]

In creating revision 2695, I forgot to update the category file and the NameMapper. I corrected this omission in a later submission and it produced revision 2698. My apologies for all the confusion.

[Norm Olsen]

A regression caused by the submissions whichproduced versions 2695 and 2698 was reported. This regression was corrected at version 2707. This correction deprecated the older REUNION and REUNIOn-ALT datums and associated coordinate reference system definitions in favor of a new datum: Region47 (defined orifinally in version 2695).