GPS / RTK monitoring

[tbohne]

• we have a uBlox GPS receiver card inside the chassis of the robot - connected to the computer via USB
• gpsd - Ubuntu GPS demon that receives the actual hardware information via USB
  • how many satellites do I see
  • connection quality (signal) - runtime
  • lat / lng -> belief state
• ROS driver that reads such information (communicates with gpsd) - publishes the info in from of navsat/fix msgs to ROS system
  • that's the /fix topic: gps_fix comes with a frequency of 1Hz or something like that.. - the gps/filtered was already processed by robot_localization node -> filtered
  • extrapolated to 10Hz or something -> filtered with itself to remove jumps
  • accumulates GPS information ad filters jumps

[tbohne]

RTK

• RTK happens on the board, we don't see the GPS data without RTK
• would be interesting to find out whether we currently receive RTK data
  • on the board is a lamp indicating that
  • find out whether that information is transferred to the computer (to gpsd)
  • we could also estimate whether we have RTK connection by looking at the covariances of the lat / lng values (many jumps -> probably not connected to RTK - with RTK, there shouldn't be any jumps at all)
  • check manual of the uBlox board + gpsd data
• generally, I can only provide monitoring for the data I get
• what is good to monitor in any case and definitely arriving at gpsd:
  • how many satellites do I see? (not sure if already part of the ROS msgs, but definitely in gpsd)
  • simulate bad GPS data: check format of the data for that..
• useful: ROS community package gpsd_client
  • example for a node I need to develop for the drive / wifi monitoring
  • ROS node that connects to some OS service and communicates information to the ROS world
  • open source - look at code
  • interesting msg there: gps_status -> use that / check whether our ROS node already uses that (contains a lot of these info like how many satellites, signal-to-noise ration, etc.)
  • based on these info, I could provide some quality estimation
  • /fix is the result of gpsd_client

[tbohne]

lat / lng is essentially a belief state