MOPEX User's Guide - IRSA

MOPEX User’s Guide
Figure 8.1: An example of tiling a FIF. Suppose NAXIS1 = 4450 and NAXIS2 = 1024. The
suggested sizes Tile Max X = Tile Max Y = 500. In this case there are 2 tiles in the ydirections
of the same size Tile Y = 512 and 9 tiles in the x-direction, 8 of the size Tile X =
494 and the last tile of the size Last Tile X = 498.
If the FIF dimensions are greater than Tile Max X or Tile Max Y, then the co-added image is tiled.
Given the dimensions of the FIF (NAXIS1 and NAXIS2) the program finds the number of the
tiles, their sizes and relative positions (offsets) with respect to the FIF. The simple algorithm
below assures that all the tiles are of almost the same size regardless of what the FIF size is (see
Figure 8.1).
N_X = NAXIS1 / (Tile Max X);
If (NAXIS1 % Tile Max X > Tile Max X/2) N_X = N_X +1;
Tile X = NAXIS1 / N_X;
Last Tile X = Tile X + (NAXIS1%N_X).
The % (modulo) operator yields the remainder from the division of the first argument by the
second. The calculations in the y-direction are identical. The tile sizes and offsets from the origin
of the FIF along with their names are written in output IPAC table coadd_tiles.tbl.
Basic Concepts in MOPEX 180
Tiling