[pdal] 'pdal info' VLR error troubleshooting

[Andrew Bell]

Each las vlr has a length. The length indicated in your vlr is incorrect in
that it would encroach into point data. Contact your data provider to get a
corrected file.

On Thu, Apr 27, 2023, 6:56 PM Speed, Cole M <cole.speed at beg.utexas.edu>
wrote:

> Hello all,
>
> I am using 'pdal info' to view the metadata for a few laz files. For
> several of the files, pdal info returns the error:
>
> PDAL: readers.las: VLR 1(SF/0) size too large -- flows into point data.
>
> I believe this may indicate that the header/VLR s longer than is expected,
> causing the metadata information to be misinterpreted. Attempting to
> troubleshoot the issue by having a look at the lasreader source code (
> https://github.com/PDAL/PDAL/blob/master/io/LasReader.cpp), I see the
> below code snippet:
>
>         if ((uint64_t)stream->tellg() + vlr.promisedDataSize >
> d->header.pointOffset)
>             throwError("VLR " + std::to_string(i + 1) +
>                 "(" + vlr.userId + "/" + std::to_string(vlr.recordId) + ")
> "
>                 "size too large -- flows into point data.");
>
> I interpret this to indicate an underlying issue related to the laz
> header/VLR, but I am unsure what specifically this means or how to resolve
> it. The files are also unreadable by QGIS (Error: 'readers.las: Invalid VLR
> - exceeds specified file range'). Insight from anyone who has encountered
> these errors or has any thoughts as to what specifically they imply about
> the header/VLR formatting of these laz files would be greatly appreciated. Thanks
> in advance!
>
> Cole Speed
>
> ---------------------
> Cole M. Speed
> Ph.D. Candidate
> Jackson School of Geosciences, University of Texas at Austin
>
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