Identify the output
Find out whether the GPS uses USB, NMEA 0183, NMEA 2000 or another interface. The adapter must be compatible with both the GPS and the computer running Signal K.
Check position and time
After configuring the source, verify that position and time update. Compare coordinates with the original device and check that stale data is recognised when the source is disconnected.
Avoid ambiguous sources
If several GPS devices are present, document which source each screen uses. A visible value is not necessarily current; check updates and keep an alternative positioning method.
A verification procedure
In port, record the GPS position and confirm that the server shows similar coordinates and a recent update time. Disconnect the source in a controlled way and observe whether the screen indicates that updates stop; reconnect it and check recovery.
When two sources exist
A radio’s internal GPS and a USB GPS may report different positions at different times. Identify the source each application uses, compare time and units, and document the configured priority. A position unchanged for several minutes may be stale rather than valid.