Possible wrong value of N4 (DF134) in IGS RTCM3EPH feed

[Altti]

Hi,

I am using IGS RTCM3EPH feed and I noticed that RTCM V3 GLONASS ephemeris message (1020) is provided with GLONASS-M N4 (DF134) value 1, even though the value should be 6 for the current year like in broadcast ephemeris.

DF 134 refers to GLONASS four-year interval number starting from 1996. And it is can be calculated in following way: M4 = ceil( ( current_year - 1996 ) / 4.0 );

Thanks much,
Altti Jokinen
NovAtel Inc.

[stuerze]

Dear Altti,
the problem should be solved. Thanks for reporting this!
Best regards, Andrea.

[Altti]

Thanks. Should the fix be already in IGS RTCM3EPH feed ?

Best regards,
Altti

[stuerze]

Dear Altti,

yes, our ephemeris streams

STR;RTCM3EPH;Assisted-GNSS;RTCM 3.3;1019(5),1020(5),1043(5),1044(5),1045(5),1046(5),1042(5);0;GPS+GLO+GAL+BDS+QZS+SBAS;MISC;DEU;50.08967;8.66458;0;1;BNC;none;B;N;2200;BKG
STR;RTCM3EPH-GLO;Assisted-GNSS;RTCM 3.2;1020(5);0;GLO;MISC;DEU;50.08967;8.66458;0;1;BNC;none;B;N;2200;BKG

available on ​http://products.igs-ip.net/ should be correct now with respect to the GLONASS-M N4 (DF134) value.

For example (see last line):

RTCM3 (2017-11-29T07:10:51.03) Type 1020 (size 45):
  SV=  2, Freq= -4, tk=10:00:00(36000s), tb=10:15:00(615min,36900s)
  Almanac health=true (valid)
  X=  8084.6376953km, X velocity=     3.0096636km/s, X acceleration=             0km/s2
  Y=-10175.5014648km, Y velocity=     0.0305700km/s, Y acceleration=   1.86265e-09km/s2
  Z=-21928.3178711km, Z velocity=     1.0896206km/s, Z acceleration=   2.79397e-09km/s2
  P1=1, P2=1, P3=1, Ephemeris health=0
  GammaN=9.09495e-13, tauN=-0.000282578, EN= 0, M=1
  GLONASS-M: P=3, ln(3)=0, delta tau=5.58794e-09, P4=1, Ft= 0, Nt= 699
  Additional Data=valid:
   NA= 699, tauC=-0.0000000154s
   GLONASS-M: N4= 6, tauGPS=-0.0000000130s, ln(5)=0

on

[Altti]

Hi,

Thanks, interestingly, I can still N4 value 1 in RTCM3EPH feed in products.igs-ip.net.
Is it sure that server has already been updated ?

Thanks,
Altti

[anonymous]

Dear Altti,

please see my answer above. Furthermore, I have monitored RTCM3EPH available at products.igs-ip.net with the following independent software tools:

• BNC (current SVN version, an release update will follow) and
• inspectrtcm

about some hours. And I cannot see other values for N4 than "6".

Best regards, Andrea.