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PointCloud and Python PDAL

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Joachim Meyer edited this page Jun 17, 2020 · 4 revisions

General Pointcloud resources:

  • What is a pointcloud ?

Wikipedia says "A point cloud is a set of data points in space".

  • ok, but why bother for ICESat-2 ?

Because ICESat-2 also provides point in space, in the form of geolocated photons (ATL03)!

  • so do we always need to think of ICESat-2 as "unstructured" pointclouds ? I thought I could use them as a set of uniform sampled elevation values along a profile...

Nah, the higher products (ATL06, ATL08) are gridded using the raw point clouds ! These have uniform spacing, which is determined by the grid size in which the raw pointcloud was aggregated ..

  • oh, so that's why we might have some luck playing with pointcloud libraries, but do we always need a pointcloud special library to analyse ATL03 ?

Who told ? basic exploration can be done using native python ecosystem itself ! See this example from Philip and also todays land ice Tutorial.

The idea here is that maybe we can use established pointcloud processing library to do independent filtering and gridding and generate a product like ATL06, ATL08.

Common Formats:

Python visualisation resources:

Open-source processing packages:

  • PDAL is specific library for pointcloud.
  • Ames Stereo Pipeline is a stereo processing library but has some essential functions for pointcloud file conversion, gridding and alignment.

PDAL resources:

Building PDAL on JupyterHub

Installing PDAL via conda does not come natively compiled with HDF support. For this, one needs to compile PDAL yourself.

Here some instructions:

conda create -n pdal-build

conda activate pdal-build

conda install laz-perf laszip sqlite libxml2 curl gdal hdf5 cmake compilers libspatialite eigen ninja zstd numpy make

git clone https://github.com/PDAL/PDAL.git pdal

cd pdal

mkdir build

cd build

CFLAGS= CXXFLAGS= CC=/srv/conda/envs/pdal-build/bin/cc CXX=/srv/conda/envs/pdal-build/bin/c++ 

cmake -G Ninja -DCMAKE_LIBRARY_PATH:FILEPATH="$CONDA_PREFIX/lib" -DCMAKE_INCLUDE_PATH:FILEPATH="$CONDA_PREFIX/include" -DBUILD_PLUGIN_HDF=ON ..

ninja

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