Export Map Operation and on-the-fly Datum Transformations

[GregCorradini]

Hello,
I can't find an explicit answer in the REST API docs, but the Export Map operation doc makes it seem like a MapServer service (regardless of the advertised spatial ref ) can return images of any spatial ref I pass in with the imageSR param. Is that true? Are there no limits on this even if the advertised projection and requested imageSR have different datums?

If someone could point be to an explicit part of the documentation that explains this support in detail I'd be a happier camper.

Thanks
Greg

[TanuHoque]

REST API does not explicitly allow to choose datum transform for REST operations supports projection on the fly. Mapservice tries to find the best matched datum transform which may not work all the time. If there is only one transformation from a given datum to the other, it works; in case of multiple transformations between two projection, the auto-picked transformation may not work.

[nicogis]

Tanu, I don't understand your answer. Ok for one datum trasformation but if I have more datum transform: "may not work". I think that behind rest esri uses ESRI.ArcGIS.ADF.ArcGISServer.MapDescription and then it runs a ExportMapImage ( http://atlas.resources.ca.gov/ArcGIS/SDK/SOAP/SOAP_Map_ExportMapImage.htm ). ESRI.ArcGIS.ADF.ArcGISServer.MapDescription has geotrasformation. Why geotrasformation isn't exposed? has it problems?

[DavidMartin]

Does this "auto-picking" of transformations continue to be the case in 10.2? If so, is there any way of discovering what transformation is being auto-picked?

For example, what would be the auto-picking logic in use behind a request to transform between WGS84 and OSGB36?