Greyhound

Exercise

This exercise uses PDAL to fetch data from a Greyhound server. Greyhound is a web server for point cloud data. You can learn more about what it is by visiting http://lidarnews.com/articles/open-source-point-cloud-web-services-with-greyhound/

See the Dublin data used in this example in your browser at

http://potree.entwine.io/data/dublin.html

  1. In your OSGeo4W Shell, navigate to the C:\Users\hobu\PDAL\exercises\translation folder.

    cd C:\Users\hobu\PDAL\exercises\translation
    
  2. View the greyhound.json file in your editor. If the file does not exist, create it and paste the following JSON into it:

    {
        "pipeline": [
            {
                "type": "readers.greyhound",
                "url":"data.greyhound.io",
                "depth_begin":0,
                "depth_end":11,
                "resource":"dublin",
                "filter":{
                    "Classification": 2
                }
            },
            {
                "type": "writers.las",
                "compression": "true",
                "minor_version": "2",
                "dataformat_id": "0",
                "filename":"just-ground.laz"
            }
        ]
    }
    

    Note

    If you use the Developer Console when visiting http://speck.ly or http://potree.entwine.io, you can see the browser making requests against the Greyhound server at http://data.greyhound.io

  3. Issue the following command in your OSGeo4W Shell.

    pdal pipeline greyhound.json
    
    ../../../_images/greyhound-command.png
  1. Verify that the data look ok:

    pdal info just-ground.laz | jq .stats.bbox.native
    
    ../../../_images/greyhound-info-verify.png
  2. Visualize the data in http://plas.io

    ../../../_images/greyhound-view.png

Notes

  1. readers.greyhound contains more detailed documentation about how to use PDAL’s Greyhound reader .
  2. As depth_end gets larger, the number of possible points goes up by nearly a factor of 4. Use the bounds option of the reader to split up the boxes you are querying to decrease the potential number of points a query might return.