In regular HSC survey processing, we'll run with a "rings" skymap to cover the entire survey area. meas_mosaic does not currently efficiently or conveniently iterate over tracts. For example:
mosaic.py /tigress/HSC/HSC --rerun price/cosmos --id field=SSP_UDEEP_COSMOS filter=HSC-R
Note the lack of a tract in the --id specifier — we want to iterate over all tracts. This is not currently possible. Instead, if we do not know the tract of interest (which the user should not be required to know), we have to iterate over all the tracts (e.g., tract=0..12345), but the user should not be required to know the number of tracts, and this is slow (and possibly memory-hungry: currently consuming 11GB on tiger3 just for 12 exposures).
We need an efficient mechanism to iterate over all tracts by not specifying any tract on the command-line.