ScanAngleRank not found

[spono]

Ciao JR, I'm having some issues with some new files I received.

Running an analysis I got this error:

> ads = clip_roi(ctg, shp, radius=fixed.radius)
> metrics = catalog_apply(ads, cloud_metrics, func = .my_metrics)
Error: object 'ScanAngleRank' not found

.my_metrics calls ScanAngleRank in a pretty regular way:

.my_metrics = ~my_metrics(X, Y, Z, ReturnNumber, Classification, ScanAngleRank,
                                        ht_slice=1, ht_max=NULL, min_pts=0, sar_thr=NULL)

I checked the data in R and it seems that ScanAngleRank is reported as ScanAngle.

> head( las@data )
          X       Y     Z   gpstime Intensity ReturnNumber NumberOfReturns ScanDirectionFlag EdgeOfFlightline Classification
1: 685999.3 5089999  0.27 336380160        86            1               1                 0                0              1
2: 685999.4 5089987 -0.24 336380160        16            2               2                 1                0              1
3: 685999.3 5089989 -0.25 336380160        52            2               2                 1                0              1
4: 685999.6 5089999  9.50 336380160         8            3               4                 1                0              1
5: 685999.0 5089997  0.46 336380160         7            4               4                 1                0              1
6: 685998.9 5089998  0.18 336380160        78            1               1                 1                0              1
   ScannerChannel Synthetic_flag Keypoint_flag Withheld_flag Overlap_flag ScanAngle UserData PointSourceID
1:              0          FALSE         FALSE         FALSE        FALSE   -13.998        0          1253
2:              0          FALSE         FALSE         FALSE        FALSE   -13.998        0          1253
3:              0          FALSE         FALSE         FALSE        FALSE   -13.998        0          1253
4:              0          FALSE         FALSE         FALSE        FALSE   -13.998        0          1253
5:              0          FALSE         FALSE         FALSE        FALSE   -13.998        0          1253
6:              0          FALSE         FALSE         FALSE        FALSE   -13.998        0          1253

As a crosscheck, I tried to load a LAZ in CloudCompare and the weird thing is that ScanAngleRank is there.

I then modified the function in order to work with ScanAngle and, in the end, I got this:

Warning messages:
1: Invalid file: the data contains a 'ScanAngle' attribute but LAS format is not 1.4 and point data format not >= 6. Use attribute 'ScanAngleRank' instead.

According to the header, is IS a 1.4 format.

> las@header
File signature:           LASF 
File source ID:           0 
Global encoding:
 - GPS Time Type: Standard GPS Time 
 - Synthetic Return Numbers: no 
 - Well Know Text: CRS is GeoTIFF 
 - Aggregate Model: false 
Project ID - GUID:        00000000-0000-0000-0000-000000000000 
Version:                  1.4
System identifier:         
Generating software:      rlas R package 
File creation d/y:        284/2022
header size:              375 
Offset to point data:     375 
Num. var. length record:  0 
Point data format:        6 
Point data record length: 30 
Num. of point records:    4986157 
Num. of points by return: 3480656 1168058 220348 117095 0 0 0 0 0 0 0 0 0 0 0 
Scale factor X Y Z:       0.01 0.01 0.01 
Offset X Y Z:             0 0 0 
min X Y Z:                683999.9 5088000 -22.16 
max X Y Z:                686000.1 5090000 42.49 
Variable Length Records (VLR):  void
Extended Variable Length Records (EVLR):  void

The only thing I know is that these LAZ derive from originally LAS file lately compressed using -I guess- Lastools.

Any idea? let me know if you need a file

[Jean-Romain]

I then modified the function in order to work with ScanAngle and, in the end, I got this:

What did you do to get this error ?

In the las specification ScanAngleRank is an integer attribute which is supposed to record the rank of the scan angle. 10 is not 10 degree but the 10th angle of the sampling device. Usually we are assuming that the value n corresponds to n degrees and it is probably what is recorded. The ScanAngle on another hand records the actual off nadir angle with decimal numbers (after conversion from raw data). So scan angle and scan angle rank are two different things and in lidR I choose to make them different. Some software may opt to call them the same but in rlas I opt to stay as close as possible to the spec.

So basically you juste have to call your metrics function

mymetrics(X,Y,Z, ScanAngle)

instead of

mymetrics(X,Y,Z, ScanAngleRank)

[spono]

mymetrics(X,Y,Z, ScanAngle)

great, that's what I did in the meatime as a workaround.

What did you do to get this error ?

(I'm out of the office, I'll let you know as soon as I replicate it)