Satellites - GPS Enable/Disable |
The GPS Enable/Disable page is used to control which satellites are enabled or are set to ignore bad health status. Each GPS satellite has two checkboxes associated with it. These control how the receiver treats each satellite. To change the settings, click on the desired checkboxes and then select OK. The Enable All button can be used as a quick way to check Enable on all satellites.
The default state on each satellite is Enabled but not Ignore Health. In this mode, the satellite's signal will be acquired and its ephemeris data decoded. If the satellite indicates that it is healthy and almanac from other satellites agrees with that, then the satellite will be used normally. That is, it will continue to be tracked, its measurements will be processed, and the information will be used to calculate positions, etc.
If the ephemeris or almanac indicate that the satellite is unhealthy, the system will avoid using the data from that satellite. Signal measurements and decoded data will not be available, the satellite will not be used in position calculations, etc. Attempts will be made periodically to track the satellite, waiting for its health to improve.
Any individual satellite can be disabled by unchecking the Enable checkbox. When this is done, the NetRS will make no attempt to track signals from that satellite. No new data will be collected and no measurements will be available for logging or processing.
The normal system response to an unhealthy satellite can be overridden by setting the Ignore Health checkbox. When this is done, the tests of ephemeris and almanac health are ignored, and the satellite is treated as if it were healthy. This would allow measurements and data to be collected from an unhealthy satellite, and would allow that information to be logged, used for position calculations, etc.
Note that Ignoring Health is potentially dangerous. Satellites can be unhealthy for a number of reasons. For example, if the L2 signal source on a satellite fails, the satellite would be marked unhealthy, but the L1 signals and the satellite data would still be perfectly useful. In that case, using the satellite would cause no serious problems. But other satellite failures can result in improper satellite time settings, corrupt satellite data, invalid signal phases, etc. These conditions could result in serious problems if the derived information were used in the NetRS for setting time, calculating positions, etc. Thus:It is not recommended that the NetRS be operated with an Ignore Health setting on any satellite.