[IGS-DCWG-129] Problematic GLONASS navigation files ...

[Oskar Sterle]

Dear Mr., Ms.,

I was doing some processing of GPS / GLONASS data on a basis of 
broadcast  ephemeris and I got extremely bad results for GLONASS data. 
After some analysis I found that the GLONASS navigation files are, in my 
opinion, incorrect. I found out that the problem is evident after leap 
second 17 introduction, where some of the broadcast navigation data, 
stored in brdcDDD0.YYg files, contain an additional 1 second in an 
epoch. As an example, in a file brdc2200.15g 
(ftp://cddis.gsfc.nasa.gov/gnss/data/daily/2015/220/15g/brdc2200.15g.Z) 
there is:

  1 15  8  8  0 45  0.0-0.151447951794D-03 0.000000000000D+00 
0.180000000000D+04
    -0.112675112305D+05-0.160253047943D+01 0.931322574616D-09 
0.000000000000D+00
0.256164208984D+04-0.266967201233D+01-0.931322574616D-09 0.100000000000D+01
    -0.227310625000D+05 0.494499206543D+00 0.186264514923D-08 
0.000000000000D+00
...
  1 15  8  8  1 15  0.0-0.151447951794D-03 0.000000000000D+00 
0.360000000000D+04
    -0.143798266602D+05-0.181855010986D+01 0.000000000000D+00 
0.000000000000D+00
-0.187464013672D+04-0.222508335113D+01-0.186264514923D-08 0.100000000000D+01
    -0.209729423828D+05 0.144630336761D+01 0.186264514923D-08 
0.000000000000D+00
...
  1 *15  8  8  1 15  1.0*-0.151447951794D-03 0.000000000000D+00 
0.360000000000D+04
    -0.143798266602D+05-0.181855010986D+01 0.000000000000D+00 
0.000000000000D+00
-0.187464013672D+04-0.222508335113D+01-0.186264514923D-08 0.100000000000D+01
    -0.209729423828D+05 0.144630336761D+01 0.186264514923D-08 
0.000000000000D+00

It can be seen that the red epoch has an increment of 1 second. Is this 
normal? Probably not, since any position of satellite R01 after 1:15:01 
is wrong for approximately 4km (1s of travel time).

Did anybody else also encountered this problem?

Oskar Sterle
University of Ljubljana, Slovenia
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