GammaLib

Launching ctlike for Fermi/LAT data analysis as described in ctools manual ( http://cta.irap.omp.eu/ctools/users/tutorials/howto/fermi/howto_fermi_fitting.html )
I’ve encountered following error

• ERROR encounterted in the execution of ctlike. Run aborted ...
• ERROR in GSkyMap::alloc_wcs(GFitsImage*): Invalid World Coordinate System code (ARC). Projection code not known. Should be one of AIT/AZP/CAR/GLS/MER/MOL/SIN/SFL/STG/TAN.

The error is caused by the presence in xml region-model diffuse source(s) based on standard diffuse templates for 3FGL catalogue (HESSJ1303-631.fits ; HESSJ1614-518.fits). These sources are just 2-d maps, but provided in ARC projection.

Please, note, that the error is there, although the Exposure map similar to the manual is explicitly built in TAN projection.

The workaround is to reproject ARC-projection sources to an other (AIT/CAR/TAN) projections. I’ve tested that after such reprojection ctlike works fine.

It would be great to add handling of ARC projection to GSkyMap.
As a temporary measure it would be great to add a caveat on Fermi/LAT ctools data analysis manual (ctlike can fail if a diffuse source in ARC projection is present in the model; in this case reprojection to AIT/TAN/CAR of this source’s template with e.g. skyview is required)