Version 5 (modified by mark1, 16 years ago) (diff)

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Processing LIDAR data from Leica ALS50

This page describes the basic steps involved in processing the Raw Scan data from the Leica ALS50 II. More information can be found here

The first stage is to post-process the GNSS data and blend it with the IMU data to get the best position and attitude of the laser scanner for the flight. This uses the IPAS Pro and Grafnav software packages on windows.

Raw scan to point cloud

This stage of the processing takes the raw scanner files and georeferences them to create a point cloud of the data. This is usually in the binary LAS format but may be output as ASCII if you wish. This uses the ALSPP software.

After running the ALSPP check the % of first returns column in the main window. This should be high (probably >95%). If not then it may be an indicator to problems with the data (such as a large % of cloud coverage)

Data QC and further processing

The final stages of the processing are to quality check the data and filter out noisy points. To do this we use the Terrasolid package within the Microstation CAD environment, and can be very time consuming. See tips on using Terrascan and also the QC section here for details on the process.

The main steps will be:

  • to remove noisy points (haze, low points and isolated points)
  • check the horizontal overlap between neighbouring lines
  • check the elevation overlap between neighbouring lines
  • check the data against OS vectors if available
  • if GCPs available then compare them against LIDAR

Further information on the data QC routines can be found here

Calibration Files

The .reg files for the ALS processing can be found in the calibration directory of the ARSF repository. After a new calibration, write the details here. October 2008