Naming Convention
There are several analysis centers that contribute to the three International GNSS Service orbits:
The final (igs), rapid (igr), and ultra-rapid (igu).
Explanation of revised sp3 format (sp3c)
The naming convention for the final and rapid are as follows ....
sssnnnnx.aaa.Z
sss - igs, igr
nnnn - GPS Week, week 0001 is Jan. 6-12, 1986
x - day of week (Sun=0 --> Sat=6, Full Week=7)
aaa - sp3=orbit, other extensions are clk,cls,erp,sum
Z - files are Unix compressed
The ultra-rapid is a 24hr predicted orbit is released four times a day and has its own convention.
sssnnnnx_hr.aaa.Z
sss - igu
nnnn - GPS Week, week 0001 is Jan. 6-12, 1986
x - day of week (Sun=1 --> Sat=6, Full Week=7)
hr - start hour (00,06,12,18)
aaa - sp3=orbit, other extensions are erp,sum,cmp.sum
Z - files are Unix compressed
