By popular request the NMEA GSA and GSV messages are now output by the Inertial+. The GSA and GSV messages help users understand the quality of the position output by GPS receivers.
The GSA message lists the active satellites, those that are being used by the GPS receiver at the moment. It also includes dilution of precision information, which is an indication of how good or poor the current satellite geometry is. When the satellites are all in a line, or clumped together, then the dilution of precision is high (poor). When the satellites are spread throughout the sky then the dilution of precision is low (good).
The GSV message lists the satellites that are in view, giving information about their signal strength and their position in the sky. Using the GSV message software can make a skyplot so that the user can see where the satellites are and understand the dilution of precision better.
The number of fields that the Inertial+ is able to set in the GSA and GSV messages depends on the GPS receiver that is connected to the Inertial+. Currently the full set of outputs is only supported when an NMEA GPS receiver is connected and configured to output GSA and GSV itself.