What are the considerations with regards to L-band and GNSS reception when working at high latitudes?

L-band Considerations

When working at high latitudes, the elevation of L-band satellites decreases. Dedicated L-band antennae such as the VERIPOS 90984 and V86 can generally track the L-band satellites down to around 10° Elevation (Approximately 70° latitude depending on exact location).  Combined antennas (GNSS+L-band) generally stop tracking L-band satellites at a slightly higher elevation.

For receiving VERIPOS corrections at high latitudes, alternative delivery methods should be considered. Some alternative means of receiving VERIPOS corrections are:

• Use of a tracking dish - VERIPOS corrections can be received via vessel Inmars\dat systems connected to the VERIPOS DGNSS receiver. Tracking dishes are capable of tracking to lower elevations.  Different Inmarsat systems are capable of tracking different L-band satellites. See FAQ What tracking dish systems can I use and what beams will they track? for more details.
• NTRIP - VERIPOS corrections sent over an internet connection. These are normally delivered via a ship’s V-SAT system or an Iridium communications system. Further details regarding NTRIP can be made available on request.

The VERIPOS Verichart software can be used to enter the worksite location and check the elevation(s) to the relevant L-band satellites. This will help identify if there are likely to be issues receiving corrections by means of conventional L-band antennae:

GNSS Considerations

At high latitudes GNSS reception can be affected because there will be fewer satellites directly above the worksite. If using GPS satellites only this could lead to a low satellite count or poor satellite geometry, both of which could potentially lead to a loss of DGNSS position.

To combat these issues, the use of GLONASS satellites in addition to GPS should be considered*. This will significantly increase the number of available satellites at any one time and also improve the geometry.

*The VERIPOS equipment/software must have the correct permissions and access codes before GPS + GLONASS solutions can be used.

GPS Satellite Sky Plot at 70°N

GPS + GLONASS Satellite Sky Plot at 70°N