In order to optimally use multiple images of the same sky area, one has to accurately map the coordinates of these image onto a common coordinate system. Commonly,the images we get are significantly deeper than reference catalogs, and hence the coordinate mappings benefit from making use of common objects in the images, even if they do not appear in reference catalogs. I will describe some technicalities of this joint fit problem, the features of some implementations, and propose some goals for the LSST implementation.
Mr. Pierre ASTIER (LPNHE)