Here GPS logging of raw carrier phase observations for PPK

Here GPS
1

Are there any solutions for storage/logging of raw GNSS carrier phase observations on both the base and rover side? The purpose is to process the trajectory by means of post processed kinematic GNSS method when RTK has failed (mainly due to loss of telemetry from base to rover). If so, then

  1. What is the maximum recording frequency and
  2. Can the raw observations be translated to RINEX for post processing with RTKLIB?
  3. Is additional hardware required for the storage of raw observations?
2

@Walter_Volkmann There is work being done to add this support for HerePro Release v1.14-rc1 · CubePilot/GNSSPeriph-release · GitHub. If you want to test the firmware extract the zip file and load HerePro_FW.bin through Mission Planner or dronecan_gui_tool. No additional hardware would be required. The rover side logs are recorded in emmc on HerePro. The recorded format is .ubx which can be loaded in RTKLib and converted to RINEX.

You will need to set parameter ROVER_ENABLE to 1. To get the logs simply connect HerePro via USB and the drive will appear on your machine.

3

Thanks for this feedback.

  1. Does this apply to the Here Pro only or will the other Here models also have that capability?
  2. At what frequency are the carrier phases recorded? - relevant because it affects the distance between trajectory points.
  3. What is the storage capacity on Base and Rover units?
  4. Any plans for the rover to record external events such as triggers and exposures in the observation file?
    Thanks in advance for your replies.
4

  1. Does this apply to the Here Pro only or will the other Here models also have that capability?
    Currently only HerePro supports this, as HerePro is the only hardware with onboard logging. There will be support added to eventually do logging other Here models over CAN, but it will be a while before that happens.

  2. At what frequency are the carrier phases recorded? - relevant because it affects the distance between trajectory points.
    The RAW measurements are recorded at 5Hz.

  3. What is the storage capacity on Base and Rover units?
    HerePro has onboard emmc of 2GB. So they can record that much worth of logs.

  4. Any plans for the rover to record external events such as triggers and exposures in the observation file?
    The current release candidate records the trigger events on GPIO 1 into Ublox TIM-TM2 message on the onboard ublox logs generated with ROVER_ENABLE 1. There will be more documentation on how to setup triggers. The setup needs to take into account 4K Ohm internal pullup to 3.3V on GPIO side and tolerance of upto 5.5V.

Base side setup is documented here: https://docs.cubepilot.org/user-guides/herepro/herepro-manual#base-module-setting-using-mission-planner

Rover side setup is not documented yet. To enable it you need to set ROVER_ENABLE parameter available through following HerePro RTK rover parameter settings section under https://docs.cubepilot.org/user-guides/herepro/herepro-manual#id-7.-rtk-manual

Please note that this feature is being actively worked upon and tested. The firmware will be released as release candidates, and once robust enough will make it as official current release. Feel free to test and report issues. You can keep track of releases here for regular updates Releases · CubePilot/GNSSPeriph-release · GitHub

5

Thanks for the update Siddharth.

Can the coordinates in the surveyed base station coordinate list be edited manually? This is relevant for the case where the GNSS base station is set up over a point for which cm-accurate absolute coordinates are already known. Ideally your set-up routine should include an option for user input of the base station coordinates. The setup routine should check these coordinates for plausibility (i.e. is the entered position within 10m of the initial stand alone solution as determined by the receiver) before sending out RTCM corrections based on the entered coordinates. (Otherwise the RTK computations may not be able to resolve the integer ambiguities - i.e. never manage to deliver “fixed” solutions.)

Setting the base up with precise absolute coordinates will allow users to directly map on a given datum without the need for further adjustments to the rover coordinates. It also obviously obviates the need to “survey” the base station position. Just a suggestion from a land surveyor’s perspective.

6

@Walter_Volkmann Mission Planner has option to record survey points. RTK GPS Correction (Fixed Baseline) — Copter documentation . There is also option to survey in using HerePro only, only single point can be surveyed in at a time, and need to use Mission Planner to enter those values through B_ parameters. HerePro Manual | CubePilot