Lidar Lite V3 Accuracy Issue

[xhr0428]

I tested Lidar Lite V3 with Uno using the Garmin library I2C example. The specs says the reading accuracy should be within ±2.5cm for <5m range and ±10cm for the rest, but my result didn't match at all.

I pointed Lidar Lite towards a wall at different distances, recorded ~1000 samples at ~30Hz rate at each location and checked reading fluctuation:

Location     Fluctuation
1m             6cm
3m             9cm
7m             17cm
11m           52cm
18m           101cm

After 20m range, I could barely get any valid reading even though the measurement range should go to 40m written on the specs.

My connection exactly followed the diagram on the specs and I tried both default and maximum range modes.
http://static.garmin.com/pumac/LIDAR_Lite_v3_Operation_Manual_and_Technical_Specifications.pdf

Could anybody help me with this? Did I receive a faulty unit?

Thanks

[mikb55]

Are you using a "70% reflective target" as per the documentation?
The device uses 905nm so there is no guarantee that something that appears reflective/white to you in the visible range is also reflective at that wavelength.

Are the values you see constant offsets or variations about a mean?

[xhr0428]

I pointed it at regular wall, I assume this should be a very normal use case.

The values are fluctuating around a mean.

[mikb55]

Do you see the same behaviour as this https://youtu.be/ddxguAzzzJE?t=596

[xhr0428]

Yes, similar. His result seems to have less fluctuations than mine. Also my test beyond at 20m was like what he had for 40m, a lot of 1s and random erroneous values with several correct readings every now and then.

[jremington]

Point it at some different walls, and let us know what happens.

[mikb55]

If you fancy a bit of decorating visit your local hardware store and look for 'heat reflecting paint'. These are loaded with various metal oxides that reflect in the near infrared.

https://curve.carleton.ca/system/files/etd/252fd1b7-cb5f-4596-8469-c5e9c6b0857c/etd_pdf/f314d9e848600f52932bea16789c1d6f/cui-studyanddevelopmentofnearinfraredreflective.pdf