Warps are the result of resampling and realigning the camera images onto regular areas (called skycells) on the sky (basically aligned N-S, E-W). How this is done depends on the particular tessellation. Different surveys may have different tessellations. A warp will generally consist of several different OTAs, therefore there are gaps between the OTAs, as well as the smaller gaps between the cells. Warps are astrometrically and photometrically calibrated.
Example of a single warp (left) and stack (right) of a galaxy at Ra=23:41:52 and Dec=-08:38:54.05