SCALED_IMU2 and RAW_IMU acceleration readings on BlueRoV2 R4

[EliotBR (Eliot)]

Hi @coanderson,

I’ve moved your post here because it’s on a more related topic.

@coanderson

all my accel and gyro values for SCALED_IMU2 are all 0 for the whole log.

Assuming you’re using our Navigator board, there is only one IMU, so only data for one IMU gets sent in the telemetry. Systems using a Pixhawk or other flight controller board may have two.

@coanderson

I’ve read on other posts recommendations to not use the RAW_IMU data for any sort of dead reckoning (or the scaled IMU for that matter, but it seems scaled is better for it if you really want to do dead reckoning)?

As per further up in this thread, ArduPilot actually sends RAW_IMU and SCALED_IMU2 with the same scaling - it’s just a difference of which piece of hardware is being read from.

@coanderson

Could this be fixed by using the dataflash logs instead of the tlogs?

Dead reckoning isn’t recommended because of both the quality and frequency of the IMU data, and because the double integration of accelerometer data into position estimates also involves doubly-integrating the error, which can lead to significant, rapid error buildup.

Dataflash logs will provide higher frequency data than the tlogs (because the autopilot records more values internally than it typically sends through telemetry), but that doesn’t help with the data quality issue (e.g. due to sensor noise), as is discussed elsewhere on the forum - this comment may be worth a read.