= LIDAR Classification = == Purpose == To identify different types of LIDAR return and what they relate to. For instance the basic groups will be: ground, vegetation, buildings and noise. For the purpose of ARSF LIDAR deliveries we just classify noisy points. These typically tend to be due to the atmospheric conditions (cloud and haze), signal noise or single isolated points. == Method == We can use the !TerraScan software or the in-house classify_las program for point classification. The !TerraScan usage can be found on other pages of the wiki. === classify_las.out === This is a c++ utility written to do basic classification on LAS files. The current classification algorithms include: * Isolated points - identify points as noise (classification 7) if there is no other point within x metres of it. * Absolute elevation - identify points as noise (classification 7) if they are above or below a given elevation. A fence can be used to only classify points within a rectangular boundary. '''Usage''' '''YOU MUST BE ON A FEDORA 12 MACHINE TO RUN THIS''' {{{ -lasfilein The LAS file to be imported and classified -lasfileout The name of the output LAS file optional flags -isolated x Run the isolated points algorithm using a distance of x metres -above x Run the absolute elevation algorithm classifying points with elevation above x metres -below x Run the absolute elevation algorithm classifying points with elevation below x metres -fence minx miny maxx maxy Use a fence whose bounds are given by minx,miny maxx,maxy }}} Currently only one method can be used per run of the software. This is due to be changed shortly. '''Example''' - to classify isolated points {{{ classify_las.out -lasfilein example.LAS -lasfileout classified.LAS -isolated 5 }}}