High Source Density Bins Description and Links[Adapted from the Explanatory Supplement.] The file consists of 80-character ASCII records, with each record containing the information for two bins (Table 1). The flag HSD is hex-encoded by band, as described for the Format of the Point Source Catalog. In this notation each band corresponds to one of the four bits of a hex digit. 12 microns corresponds to bit 0 (Least significant Bit) and 100 microns to bit 3, etc. If a band went through high source density processing, then the appropriate bit in the hex digit is set. Thus, if high source density rules were invoked at 25, 60, and 100 microns, HSD would have the value 1110 (binary) = E (hex). Ecliptic bins start at the ecliptic north pole and step around the sky in bands of constant ecliptic latitude, stepping 1° southward after completing each band. The length of the bin in ecliptic longitude is adjusted for the cosine of the ecliptic latitude to maintain an approximately constant area.
Table 1. Format of the High Source Density Bins File
Start Name Description Units Format
00 BINNUM SDAS Bin Number --- I6
06 HSD Bands processed --- A2
for high source
density, hex
encoded by band
08 LAMBDA Ecliptic longitude deg F10.5
of bin center
18 BETA Ecliptic latitude deg F10.5
of bin center
28 LENGTH Length of bin in deg F10.5
ecliptic longitude
38 SPARE 2 spare bytes --- 2A1
40-79 Bytes 00-39 are
repeated for next bin
FORTRAN programs are given below to convert from bin number to ecliptic coordinates and vice versa. There is a known bug in the computation of bins at ecliptic latitude 60°, causing bin 2842 to be skipped. The following program, while incorrect in this way, will give results consistent with the bin numbers used in the data processing. To avoid problems with roundoff errors within a few arcseconds of bin boundaries, all arithmetic should be calculated in double precision. Right Click here to download the programs shown below. C CONVERT AN ECLIPTIC POSITION TO BIN NUMBER |
