Internal error in C_interpolate_delaunay

[wiesehahn]

dont want to bother you with issues in yet another repo, but I just ran into the following

> library(lidR)
> library(lidRalignment)
> 
> als_file <- "C:/Users/jwiesehahn/arbeit/sideprojects/lidar-biodiversity-plots/data/laz/NI-ND-10.laz"
> mls_file <- "J:/ni/mls/2026/diversa/3dm/NI-ND-10.laz"
> 
> options(lidR.progress = FALSE)
> radius = 50
> 
> # align MLS to ALS
> alignment <- AlignmentScene$new(als_file, mls_file)
> alignment$set_ref_is_ground_based(FALSE)
> alignment$set_mov_is_ground_based(TRUE)
> alignment$set_radius(radius)
> alignment$align()

Reading reference point cloud...
Reading point cloud to align...                                                 
Checking for pre-classified ground points...                                    
  Reference point cloud has ground points...
Clipping point clouds with a buffer...
Cleaning noise points...
Classifying ground points...
 Skip reference point cloud.
Clipping point clouds...
Extracting features to align from reference point cloud...
 Computing Digital Terrain Model...
 Computing Canopy Heigh Model...
Extracting features to align from moving point cloud...
 Computing Digital Terrain Model...

Error: Internal error in C_interpolate_delaunay: xy coordinates were not converted to integer. Scale factors are likely to be invalid.

probably the data is erroneuous, havent worked much with it yet.

[Jean-Romain]

You may have a weird scale factor ? I need to manage that better for years. But I'm already working way more than I should... Hard to find free time.

[wiesehahn]

no worries, just in case

> hdr <- lidR::readLASheader(mls_file)
> hdr
File signature:           LASF 
File source ID:           0 
Global encoding:
 - GPS Time Type: GPS Week Time 
 - Synthetic Return Numbers: no 
 - Well Know Text: CRS is GeoTIFF 
 - Aggregate Model: false 
Project ID - GUID:        00000000-0000-0000-0000-000000000000 
Version:                  1.2
System identifier:        libLAS 
Generating software:      libLAS 1.8.1 
File creation d/y:        98/2026
header size:              227 
Offset to point data:     227 
Num. var. length record:  0 
Point data format:        1 
Point data record length: 28 
Num. of point records:    142291590 
Num. of points by return: 0 0 0 0 0 
Scale factor X Y Z:       1e-04 1e-04 1e-04 
Offset X Y Z:             32563684 5894485 117.3607 
min X Y Z:                32563563 5894353 112.3607 
max X Y Z:                32563807 5894606 181.3607 
Variable Length Records (VLR):  void
Extended Variable Length Records (EVLR):  void

[Jean-Romain]

1e-4 with geographic coordinates. That introduces floating point accuracy issue. The file is valid. You can rescale to 0.001. Arguably you don't need a tenth of millimeter accuracy for a sensor that doesn't have a centimeter accuracy.

[wiesehahn]

true, so the way to go is to run something like this first?

las <- readTLS(mls_file)
las <- las_rescale(las, xscale = 0.001, yscale = 0.001)
writeLAS(las, ofile)

[Jean-Romain]

That should work