Ping2 time lag bug creates a saw tooth patten in bathymetry at ends of waypoint paths

Blue Robotics Vehicles BlueBoat
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I have noticed that the Ping2 mounted on my Blueboat has a time lag bug of about 1.5 to 2 seconds. I have a survey grade RTK GNSS (not ublox) mounted and it is connect to the navigator on the RP. I have attaced an image that illustrates the issue created when the ping sounding is attached to a GNSS location recored 1.5 - 2 seconds after the location of the sounding. boat travel speed is 1m/s.

Also, the ping2 using the simple ping2 survey app drops sounding at regular intervals?!

Question: how do I resolve these bugs?

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1 Like
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Hi @scriffij -
Welcome to the forums! I’m excited you’re using the BlueBoat and to confirm, you used the Simple Ping Survey app to collect this data?
Can you share vehicle autopilot logs from the same mission this data was collected with, as well as BlueOS logs (found under the gear in the lower left of BlueOS)?

I’m not sure I understand why you think the bathymetry is lagging the gps based on the “sawtooth” pattern. To me it looks like artifacts from interpolation?

The extension is recording data at 2Hz, but this rate could be increased. Is your survey grade GPS configured for primary use in the vehicle? The extension is recording the lat/long used by the autopilot, which could be the default GPS if it is still connected and configured as the primary location source.

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Thanks for the reply @tony-white
Yes we are using the Simple Ping Survey app to record the data.
We have disconnected the ublox gnss that came with the boat and disabled it in the Parameters. we use a Septentrio Asterx-m GNSS as the only GNSS connected and it receives RTK via missionplanner RTK inject.

I beleive that there is a lag in the recording of the soundings as when I reposition my depths by about 1.5 seconds in excel table, the saw tooth patten is all but gone.

I will get the logs ASAP

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I see on anothre post that @jshields in a post on 10 June 2020 had same problem with ‘Ping1D lag in ceceiving measurements’ post.

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@tony-white I have conducted some more testing and it apperas that when there are multiple functions happining, Simple Ping Survey Logging, Mission Planner logging, RTK inject
 The lag in wtiting the sonar measurement to the record file is 1-1.5 seconds. when Mission Planner Logging is dissbaled and RTK inject is dissabled the lag in writing the sonar measures to the record files is about 0.25-0.5 seconds. please see the two images below.

There is a clear issuewith the performance of the RPi 4 running Ardupilot, Linix and Blue OS resources. is it possible to turn off the Blue OS system logging as well to remove as much of this lag as possible. or would a RPi 4B with 8MB ram work better?

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Hi @scriffij
I haven’t forgotten about this potential issue, and wanted to follow up

Thanks!

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@tony-white
I have replaced the RPi with an 8GB model and have it booting from a Samsung T7 SSD. I have also included an OEM powered USB 3.0 hub (taking power from the main rail) with four powered ports each receiving 2A. I have upgraded the the GNSS to a Holybro-H RTK with a Septentrio Mosaic-H chipset. GNSS is also getting power from main power rail not the navigator hat and the UBLOX GNSS is unplugged and dissabled.

Sequencial write speed difference:
before with SD card ~ 30000 bytes per second
now with SSD ~ 330000 bytes per second

I will be testing again either this week or next week but the RPi + SSD upgrade may have solved the issue. will confirm after testing.
Regards
Jason