The sample data used in this lesson is 3DEP lidar data in two LAZ files, containing LAS version 1.2, located in Madison, MS, USA.
Prior to commencing this lesson, please download the sample data:
LAS(er) files are an open format defined by ASPRS. LAS files contain the spatial location of points along with additional attribution
stored in metadata fields for each point.
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The LAS file is intended to contain LIDAR (or other) point cloud data records.
The data will generally be put into this format from software (e.g. provided by LIDAR hardware vendors)
which combines GPS, IMU, and laser pulse range data to produce X, Y, and Z point data.
The intention of the data format is to provide an open format that allows different LIDAR hardware
and software tools to output data in a common format.*
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LAZ files are a losslessly compressed version of LAS files created and maintained by rapidlasso GmBH which
significantly reduce the storage requirements of LAS files. uniDEM uses LASzip to read and write LAZ files.
The following section discusses some key differences between LAS version 1.2 and version 1.4 by focusing on LAS CLASS and Flag differences.
Low Vegetation (3) and Medium Vegetation (4) have been used to classify both buildings and vegetation.
Polygons can be drawn around buildings to correct the LAS Classification.
Reclassify Building
Click into bottom right window
Press P for the polygon drawing tool
While holding Shift right click to add vertices around one building
Reclassify Building
Within the LIDAR tab
Click Set From Drawing
Select the Madison dataset and LAZ files
In "Select existing classes to reassign:" pick
3: Low Vegetation
4: Medium Vegetation
In "Select new class:" pick
6: Building
Click OK
Click OK to accept all geometries ABOVE
Click OK to accept all geometries BELOW
Observe: Medium and High Vegetation reclassified to Building (6), but Ground (2) is unchanged.