LIDAR DATA PROCESSING

Lidar points can be classified into a number of categories including bare earth or ground, top of canopy, and water. The different classes are defined using numeric integer codes in the LAS files.

A LiDAR system uses a laser, a GPS and an IMU to estimate the heights of objects on the ground. Discrete LiDAR data are generated from waveforms — each point represent peak energy points along the returned energy. Discrete LiDAR points contain an x, y and z value. The z value is what is used to generate height.

 

Translate between point cloud and other data formats. …

Combine point clouds with other data formats. …

Inspect LiDAR point components and values. …

Change a point cloud’s coordinate system. …

Tile LiDAR data to speed up processing time. …

Clip to a specific region in a point cloud. …

Reduce the number of points in a LiDAR dataset.

 

Lidar (light detection and ranging) is an optical remote-sensing technique that uses laser light to densely sample the surface of the earth, producing highly accurate x,y,z measurements. … Lidar produces mass point cloud datasets that can be managed, visualized, analyzed, and shared using ArcGIS.

While LiDAR is a technology for making point clouds, not all point clouds are created using LiDAR. … Photogrammetric point clouds have an RGB value for each point, resulting in a colourised point cloud.

 

Point Classification (ground, water, vegetation, building, power lines).  While similar in concept to the Supervised and Unsupervised classification for satellite imagery, for LIDAR the classification relies on the geometric position of the return relative to its neighbors, and the first/last return category (if there are multiple returns for a single pulse, only the last could be on the ground).  Classification can be a processing intensive operation, and many LIDAR data sets have undergone limited classification. Ground is almost always included in a LAS file, as it is needed to create a DTM. The commonly used versions of the LAS format (1.2 and 1.3) has 8 classification categories pre-defined and can handle up to 32; the newer version (1.4), which has still not been widely used, has about 20 predefned classes and can handle 256.

 

Ground classification is almost always included in a LAS files from national mapping agencies, as it is needed to create a DTM.

The LAS format includes point classifications. 

 

Every lidar point can have a classification assigned to it that defines the type of object that has reflected the laser pulse. Lidar points can be classified into a number of categories including bare earth or ground, top of canopy, and water.