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Dear Mr., Ms.,<br>
<br>
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
(<a class="moz-txt-link-freetext" href="ftp://cddis.gsfc.nasa.gov/gnss/data/daily/2015/220/15g/brdc2200.15g.Z">ftp://cddis.gsfc.nasa.gov/gnss/data/daily/2015/220/15g/brdc2200.15g.Z</a>)
there is:<br>
<br>
<tt> 1 15 8 8 0 45 0.0-0.151447951794D-03 0.000000000000D+00
0.180000000000D+04</tt><tt><br>
</tt><tt> -0.112675112305D+05-0.160253047943D+01
0.931322574616D-09 0.000000000000D+00</tt><tt><br>
</tt><tt>
0.256164208984D+04-0.266967201233D+01-0.931322574616D-09
0.100000000000D+01</tt><tt><br>
</tt><tt> -0.227310625000D+05 0.494499206543D+00
0.186264514923D-08 0.000000000000D+00</tt><tt><br>
</tt><tt>...</tt><tt><br>
</tt><tt> 1 15 8 8 1 15 0.0-0.151447951794D-03
0.000000000000D+00 0.360000000000D+04</tt><tt><br>
</tt><tt> -0.143798266602D+05-0.181855010986D+01
0.000000000000D+00 0.000000000000D+00</tt><tt><br>
</tt><tt>
-0.187464013672D+04-0.222508335113D+01-0.186264514923D-08
0.100000000000D+01</tt><tt><br>
</tt><tt> -0.209729423828D+05 0.144630336761D+01
0.186264514923D-08 0.000000000000D+00</tt><tt><br>
</tt><tt>...</tt><tt><br>
</tt><tt> 1 </tt><tt><font color="#cc0000"><b>15 8 8 1 15 1.0</b></font></tt><tt>-0.151447951794D-03
0.000000000000D+00 0.360000000000D+04</tt><tt><br>
</tt><tt> -0.143798266602D+05-0.181855010986D+01
0.000000000000D+00 0.000000000000D+00</tt><tt><br>
</tt><tt>
-0.187464013672D+04-0.222508335113D+01-0.186264514923D-08
0.100000000000D+01</tt><tt><br>
</tt><tt> -0.209729423828D+05 0.144630336761D+01
0.186264514923D-08 0.000000000000D+00</tt><br>
<br>
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).<br>
<br>
Did anybody else also encountered this problem?<br>
<br>
Oskar Sterle<br>
University of Ljubljana, Slovenia<br>
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