SBAS Position Mode
A receiver can compute a more accurate position by using Satellite Based Augmentation System (SBAS) corrections. These corrections allow a receiver to mitigate clock, orbital, and ionospheric errors.
Hexagon | NovAtel receivers can be configured to compute an SBAS position by using the SBASCONTROL command. By default, the receiver does not track SBAS satellites or use SBAS corrections.
When using the SBASCONTROL command, the receiver can be configured to use the SBAS system for the current region (if one is available), or the system of a user’s choosing. In 7.08.00, the supported systems are WAAS, EGNOS, MSAS, and GAGAN. Here are example commands with descriptions:
SBASCONTROL ENABLE- Automatically determines the satellite system to use and prevents the receiver from using satellites outside of the service area
SBASCONTROL ENABLE WAAS- Uses only corrections from WAAS satellites
SBASCONTROL ENABLE EGNOS- Uses only corrections from EGNOS satellites
In addition to the currently supported systems, the receiver can also be configured to use unsupported newer systems with the SBASCONTROL command. An example is BDSBAS. For example:
SBASCONTROL ENABLE 130- Uses only corrections from PRN 130
Here are the PRN assignments for each SBAS system In the October 2020 version, these systems are included, although some are not currently operational:
- ASAL (Algeria)
- BDSBAS (China)
- EGNOS (Europe)
- GAGAN (India)
- KASS (Korea)
- MSAS (Japan)
- NSAS (Nigeria)
- QZSS (Japan)
- SDCM (Russia)
- SPAN (Australia and New Zealand)
- WAAS (United States)
With SBASCONTROL, the receiver can also be configured to use corrections from a satellite even if it is in test mode (by default it does not use satellites in test mode). For example, this command could be used if PRN 130 is in test mode:
SBASCONTROL ENABLE 130 ZEROTOTWO
In the BESTPOS log, the receiver reports the position type. All SBAS positions are reported as “WAAS”, regardless of which SBAS system is used. The SBAS satellite is reported in the stn id.
For instance, in this log the receiver is using corrections from PRN 131, which is WAAS.
<BESTPOS COM1 0 65.0 FINESTEERING 2135 163825.000 02000000 cdba 16407
< SOL_COMPUTED WAAS 51.15043942726 -114.03068830774 1100.1247
-17.0000 WGS84 0.6922 0.6044 1.4372 "131" 4.000 0.000 39 11 11 11 00 06 00 03
At this time, SBAS corrections are not broadcast for all GNSS constellations. To compute even more accurate positions, it is recommended to use RTK or PPP.