Changeset 10946 in ntrip for trunk/BNC/src/bnchelp.html

Timestamp:

Jun 24, 2026, 4:39:53 PM (3 weeks ago)

Author:

stuerze

Message:

added GLONASS-M yaw-fixed attitude model for the APC/CoM offset applied when saving SP3 files, reducing along-track/cross-track errors near the orbit noon/midnight points

File:

• trunk/BNC/src/bnchelp.html (modified) (1 diff)

trunk/BNC/src/bnchelp.html

@@ -5640 +5640 @@
 </p>
 <p>
+For GLONASS satellites, that APC/CoM offset is rotated into the satellite-fixed frame using the satellite's
+yaw attitude. BNC assumes the nominal Sun-pointing yaw-steering law used for the other GNSS systems, except
+close to the orbit noon and midnight points when the Sun's elevation above the orbital plane (the 'beta'
+angle) is small. There, GLONASS-M satellites are known to stop tracking that law and instead hold the yaw
+angle fixed, following the model described in Dilssner, Springer, Flohrer, Dow (2011), 'The GLONASS-M
+satellite yaw-attitude model', Advances in Space Research 47(1), 160-171. Without that correction, the
+converted GLONASS CoM position can be off by several decimeters in the along-track and cross-track
+components in that situation. The maximum yaw rate used to decide when GLONASS-M can no longer follow the
+nominal law (0.25 deg/s) is taken from the literature and not calibrated against any specific satellite, so
+results should be checked against independently known attitude or orbit information where high accuracy on
+GLONASS is required.
+</p>
+<p>
  Note that clocks in the SP3 orbit files are not corrected for the conventional periodic relativistic effect.
 </p>