[pdal] filters.hag_dem not generating HeightAboveGround output

[Dom Jaskierniak]

Hi,

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.

For it to work, it was necessary to put in "minor_version": 4 in:

                    {
                        "type": "writers.las",
                        "filename": output_file,
	          "minor_version": 4  # Ensure LAS 1.4 format	
                        "extra_dims":"HeightAboveGround=float32"
                    }

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.

Regards,
Dom



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Today's Topics:

   1. filters.hag_dem not generating HeightAboveGround output
      (Dom Jaskierniak)


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Message: 1
Date: Tue, 23 Jul 2024 10:03:36 +0000
From: Dom Jaskierniak <dom.jaskierniak at environment.nsw.gov.au>
To: "pdal at lists.osgeo.org" <pdal at lists.osgeo.org>
Subject: [pdal] filters.hag_dem not generating HeightAboveGround
	output
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	<MEYPR01MB7640BCD29349AA45BA7CA91289A92 at MEYPR01MB7640.ausprd01.prod.outlook.com>
	
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Hi,

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.


# Generate the pipelines_SubGrid for each grid cell
    pipelines_SubGrid = []

    for x in range(min_x, max_x, grid_size):
        for y in range(min_y, max_y, grid_size):
            output_file = f"{output_dir}/tile_{x}_{y}.las"

            pipeline_grid_las = {
                "pipeline": [
                    {
                        "type": "readers.las",
                        "filename": input_file,
                        "spatialreference": "EPSG:4326"
                    },
                    {
                        "type": "filters.crop",
                        "bounds": f"([{x},{x + grid_size}], [{y},{y + grid_size}])"
                    },
                    {
                        "type":"filters.hag_dem",
                        "raster": dem_file
                    },
                    {
                        "type": "writers.las",
                        "filename": output_file,
                        "extra_dims":"HeightAboveGround=float32"
                    }
                ]
            }
            pipelines_SubGrid.append(pipeline_grid_las)


            ##########################
            pdal_pipeline = pdal.Pipeline(json.dumps(pipeline_grid_las))
            pdal_pipeline.execute()

Thanks in advance!


Regards,
Dom

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