<div dir="ltr"><div>There is nothing that wasn't working as far as I can tell. You wrote a version 1.2 file with an extra dimension "HeightAboveGround". This is allowed by the 1.2 specification. PDAL writes an "extra_dims" VLR if there are extra dimensions written to the file. It does this for all minor versions, even though the VLR wasn't defined until version 1.4. PDAL will read this VLR on a 1.2 file if you tell it to (see the "use_eb_vlr" option), but you can also explicitly tell PDAL what data is tacked on to the end of a standard point record with the "extra_dims" option.<br><br>The LAS specification isn't too long and is worth a read if you are going to store data in the LAS format.</div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Jul 24, 2024 at 1:36 AM Dom Jaskierniak via pdal <<a href="mailto:pdal@lists.osgeo.org">pdal@lists.osgeo.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi,<br>
<br>
I found that filters.hag_dem was not generating HeightAboveGround output because I was working with a LAS 1.2 format, which does not support extra dimensions.<br>
<br>
For it to work, it was necessary to put in "minor_version": 4 in:<br>
<br>
{<br>
"type": "writers.las",<br>
"filename": output_file,<br>
"minor_version": 4 # Ensure LAS 1.4 format <br>
"extra_dims":"HeightAboveGround=float32"<br>
}<br>
<br>
It would be helpful for all operations that require extra dimensions to check the LAS format first and throw a warning if it format is not compatible with extra dimensions.<br>
<br>
Regards,<br>
Dom<br>
<br>
<br>
<br>
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1. filters.hag_dem not generating HeightAboveGround output<br>
(Dom Jaskierniak)<br>
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Message: 1<br>
Date: Tue, 23 Jul 2024 10:03:36 +0000<br>
From: Dom Jaskierniak <<a href="mailto:dom.jaskierniak@environment.nsw.gov.au" target="_blank">dom.jaskierniak@environment.nsw.gov.au</a>><br>
To: "<a href="mailto:pdal@lists.osgeo.org" target="_blank">pdal@lists.osgeo.org</a>" <<a href="mailto:pdal@lists.osgeo.org" target="_blank">pdal@lists.osgeo.org</a>><br>
Subject: [pdal] filters.hag_dem not generating HeightAboveGround<br>
output<br>
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<br>
Hi,<br>
<br>
I tried to generate HeightAboveGround values (using filters.hag_dem) and had no success with below code. The code successfully crops the las file but the output's metadata suggests there is no HeightAboveGround value. I tried to output the las files attributes in a text output to investigate and this also provides no extra dimension "HeightAboveGround". Any help would be appreciated.<br>
<br>
<br>
# Generate the pipelines_SubGrid for each grid cell<br>
pipelines_SubGrid = []<br>
<br>
for x in range(min_x, max_x, grid_size):<br>
for y in range(min_y, max_y, grid_size):<br>
output_file = f"{output_dir}/tile_{x}_{y}.las"<br>
<br>
pipeline_grid_las = {<br>
"pipeline": [<br>
{<br>
"type": "readers.las",<br>
"filename": input_file,<br>
"spatialreference": "EPSG:4326"<br>
},<br>
{<br>
"type": "filters.crop",<br>
"bounds": f"([{x},{x + grid_size}], [{y},{y + grid_size}])"<br>
},<br>
{<br>
"type":"filters.hag_dem",<br>
"raster": dem_file<br>
},<br>
{<br>
"type": "writers.las",<br>
"filename": output_file,<br>
"extra_dims":"HeightAboveGround=float32"<br>
}<br>
]<br>
}<br>
pipelines_SubGrid.append(pipeline_grid_las)<br>
<br>
<br>
##########################<br>
pdal_pipeline = pdal.Pipeline(json.dumps(pipeline_grid_las))<br>
pdal_pipeline.execute()<br>
<br>
Thanks in advance!<br>
<br>
<br>
Regards,<br>
Dom<br>
<br>
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</blockquote></div><br clear="all"><div><br></div><span class="gmail_signature_prefix">-- </span><br><div dir="ltr" class="gmail_signature">Andrew Bell<br><a href="mailto:andrew.bell.ia@gmail.com" target="_blank">andrew.bell.ia@gmail.com</a></div></div>