Problems in exporting LAS file after intensity normalization.

[rorai-neto]

I am performing intensities normalization in my LiDAR data. On the first attempt to perform the track_sensor, an error message appears

"Error: After keeping only first and last returns of multiple pulses returns, 16 pulses still have more than 2 points. This dataset is corrupted and gpstime is likely to be invalid. In addition: Warning message: There were 12 duplicated points. They were removed for processing. "

So I fixed it using the following:

sectorder(las@data, gpstime, UserData, Z)
las@data[, `:=`(ReturnNumber = 1:.N, NumberOfReturns = .N), by = .(gpstime, UserData)]
las = las_update(las)

Afterwards, I can run the track_sensor, calculate the range and normalize the intensities.

However, when i try to export the point cloud after the normalization, the following error message appears:

"Error: Invalid data: ReturnNumber is not an unsigned integer on 3 bits"

What does this message mean, and is it possible to fix this error?

Thanks in advance for the help. All the best.

[Jean-Romain]

In

las@data[, `:=`(ReturnNumber = 1:.N, NumberOfReturns = .N), by = .(gpstime, UserData)]

You have one or several groups with more than 7 points. Thus you are assigning a return number > 7 which is not possible in a LAS file version < 1.4. I can't say more without a reproductible example. The dataset was originally invalid, renumbering the point was unlikely to fix the problem. You must identify your problem first.

[wiesehahn]

thats good to know I was'nt aware of this 3bit encoding

[rorai-neto]

In

las@data[, `:=`(ReturnNumber = 1:.N, NumberOfReturns = .N), by = .(gpstime, UserData)]

You have one or several groups with more than 7 points. Thus you are assigning a return number > 7 which is not possible in a LAS file version < 1.4. I can't say more without a reproductible example. The dataset was originally invalid, renumbering the point was unlikely to fix the problem. You must identify your problem first.

Thank you very much for your reply. I used the las_check and I have the follow message

Checking the data

• Checking coordinates... ✓
• Checking coordinates type... ✓
• Checking coordinates range... ✓
• Checking coordinates quantization... ✓
• Checking attributes type... ✓
• Checking ReturnNumber validity... ✓
• Checking NumberOfReturns validity... ✓
• Checking ReturnNumber vs. NumberOfReturns... ✓
• Checking RGB validity... ✓
• Checking absence of NAs... ✗ The following attributes contain NAs: Deviation
• Checking duplicated points... ⚠ 51 points are duplicated and share XYZ coordinates with other points
• Checking degenerated ground points... skipped
• Checking attribute population... 🛈 'ScanDirectionFlag' attribute is not populated
• Checking gpstime incoherances ✗ 2182 pulses (points with the same gpstime) have points with identical ReturnNumber
• Checking flag attributes... ✓
• Checking user data attribute... ✓ Checking the header
• Checking header completeness... ✓
• Checking scale factor validity... ✓
• Checking point data format ID validity... ✓
• Checking extra bytes attributes validity... ✓
• Checking the bounding box validity... ✓
• Checking coordinate reference system... ✓ Checking header vs data adequacy
• Checking attributes vs. point format... ✓
• Checking header bbox vs. actual content... ✓
• Checking header number of points vs. actual content... ✓
• Checking header return number vs. actual content... ✓ Checking coordinate reference system...
• Checking if the CRS was understood by R... ✗ EPSG code 32767 unknown Checking preprocessing already done
• Checking ground classification... no
• Checking normalization... no
• Checking negative outliers... ✓
• Checking flightline classification... yes Checking compression
• Checking attribute compression...
  • ScanDirectionFlag is compressed
  • Classification is compressed
  • Synthetic_flag is compressed
  • Keypoint_flag is compressed
  • Withheld_flag is compressed
  • UserData is compressed
  • PointSourceID is compressed

If it helps, attached is the link to download the point cloud tile. https://www.dropbox.com/sh/0dtvj0iice4i7h2/AABJSs1YT--zH2ccaLQ7gtIYa?dl=0

Thank you very much.

[Jean-Romain]

I see

✗ 2182 pulses (points with the same gpstime) have points with identical ReturnNumber

However it does not use UserData for multibeam laser. So you may have less than this number if your sampling device is multibeam

[rorai-neto]

I see

✗ 2182 pulses (points with the same gpstime) have points with identical ReturnNumber

However it does not use UserData for multibeam laser. So you may have less than this number if your sampling device is multibeam

I see. Thank you very much. Do you know how can i fix this to proceed with the intensities normalization? All the best.