OBSERVATORY COORDINATE FILE (typically 'obsys.dat')

This file contains geographical locations of observatories.  There is
one line per observatory.  

Historically, the information in the first line was used
for TOAs tagged with observatory number 1, the second line for number
2, and so on.  The tenth line corresponds to observatory 'a', the
eleventh to 'b', and so on.  This behavior is still invoked
if column 71 (observatory number) is blanked.  However, an
observatory number ('1'-'9' or 'a'-'z') in column 71 will now
override the default assignment (based on position in the file).

    Col       Item
   -----     ---------------
    1-15     coordinate 1
   16-30     coordinate 2
   31-45     coordinate 3
   48-48     flag
   51-62     observatory name
   71-71     observatory number
   74-75     observatory code

If the flag is blank or zero, the coordinates are taken to be latitude
(ddmmss.ss), longitude (ddmmss.ss), and elevation (m).  If the flag is
non-blank, the coordinates are taken as X, Y, Z (m) about the
geocenter.

The observatory code is a 2-character code used in ITOA format.