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I am implementing a C++ application that must produce DEMs from LIDAR data. I am following the next workflow:

  • Write .las files from lidar data.
  • Use PCL algorithms to transform/filter the point cloud.
  • Use GDAL/OGR to create the raster/grid.
  • Create a 3D model (.obj) from raster.

In this process I am doing the next file conversions:

  • From ".las" to ".pcd" (To work with PCL).
  • From ".pcd" to "vector format" (i.e. "ESRI Shapefile") (To work with GDAL).
  • From "vector format" to "raster format" (i.e. ".tif") (To generate the DEM).
  • From "raster format" to ".obj" (To visualize the DEM in 3D).

I'm using gdal_grid to create the grid from vector format file and gdal_dem to create the DEM using GDAL interpolation algorithms.

I'm not sure If this is the best way to create a DEM from .las files. I want to use third-party libraries to transform, filter or interpolate the point cloud and PCL/GDAL have these tools.

Anyone with experience with DEMs can give me information / advice?

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If you're comfortable building software from source and are on a Unix flavor or OSX, you can go from .las to DEM using PDAL and points2grid. If you're on Windows, I have no idea if you'll be able to get points2grid to build, but you could try.

Both PDAL and points2grid have C++ APIs that you could integrate into your own C++ application. You can also use PDAL's command line executable to create DEMs.

The short instructions for a Unix/OSX system to get a points2grid-enabled PDAL command-line executable are:

  • Make sure you have cmake; use your favorite package manager to install
  • Download points2grid from Github: git clone https://github.com/CRREL/points2grid.git
  • Build and install points2grid:

    cd points2grid && cmake . && make && make install && cd ..

    If you don't have write access to /usr/local, change that last bit to sudo make install

  • Download PDAL from Github: git clone https://github.com/PDAL/PDAL.git

  • Build and install PDAL with points2grid support:

    cd PDAL && cmake . -DBUILD_PLUGIN_P2G=ON && make && make install && cd ..

    Same caveat to make install as above

  • Write a pipeline xml file to describe your gridding process (run points2grid --help for more information about the points2grid options):

    <?xml version="1.0" encoding="utf-8"?>
    <Pipeline version="1.0">
     <Writer type="writers.p2g">
      <Option name="grid_dist_x">6.0</Option>
      <Option name="grid_dist_y">6.0</Option>
      <Option name="filename">outfile</Option>
      <Option name="output_type">mean</Option>
      <Option name="output_type">idw</Option>
      <Option name="output_format">grid</Option>
      <Reader type="readers.las">
       <Option name="filename">mylasfile.las</Option>
    </Reader>
    

  • Use pdal pipeline to create your DEM:

    pdal pipeline mypipeline.xml

That should create some outfile.xxx raster files.

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