We are using OS1-128 for an application. When we decoded the pcap file to extract points, we get many points with reflectivity as 0. These does not seem to correspond to areas where the objects are dark or a longer range. Although the intensity values seem to be quite low (median of intensity values are around 30 for 0 reflectivity, intensity range is from 0 to 65535) for the points whose reflectivity is 0. Is there something fundamentally wrong I could be doing? Or is this expected?
This is normal. As of firmware 3.1, a reflectivity value of 0 will always be tied to a range reading of 0, which is a non-detection. (Prior to fw3.1 we allowed returns with valid non-zero range values to round their reflectivity values to 0, which was confusing. We now floor all valid reflectivities at “1”.) Calibrated reflectivity can only be calculated when the range is known because the firmware calibration correction is largely range-dependent.
Intensity - known as SIGNAL in the documentation - is the raw signal photon count for a given pixel. Even when we do not have sufficient confidence to have a detection and report a range return, we still know the raw photon counts that were involved.
The enviroment you operate in has a big impact on how many returns you should expect in any environment. An indoor enviroment might have valid range/reflectivity on over 90% of pixels, while an outdoor flat field may give you <50% valid returns. We would need to see screenshots to further diagnose your particular environment.
Here is a scan of the Colosseum where you can see that the sky points in the red AOI have zero range and zero reflectivity.
