Intensity is a measure, collected for every point, of the return strength of the laser pulse that generated the point. It is based, in part, on the reflectivity of the object struck by the laser pulse.
Reflectivity is a function of the wavelength used, which is most commonly in the near infrared. The strength of the return varies with the composition of the surface object reflecting the return.
Intensity is used as an aid in feature detection and extraction, in lidar point classification, and as a substitute for aerial imagery when none is available. Intensity is relative and not quantifiable; you cannot expect the same value off the same target from flight to flight or from elevation to elevation.
If the lidar data includes intensity values, you can make images from them that look similar to black-and-white aerial photos. Using ArcGIS Pro, you can create intensity imagery from lidar data.
Intensity image creation
You can create a raster intensity image in ArcGIS Pro. The lidar data must be stored in LAS format, and the data vendor must have recorded the point intensity values in those files. Intensity values, according to the LAS specification, are normalized to an unsigned 16-bit range of 0-65535. This is to ensure that data from different sensors can be merged.
Note:
To confirm that the data has intensity values recorded, review the statistics for some of the LAS files of the LAS dataset.
The first step in making an intensity image in ArcGIS Pro is to create a LAS dataset. To create a LAS dataset in ArcGIS Pro, you can use either the Create LAS Dataset geoprocessing tool or the Catalog pane. Once you create the LAS dataset, you can visualize the point cloud by adding the layer to a map or scene.
Then, use the LAS Dataset To Raster geoprocessing tool to create the intensity raster image.
The following are recommendations for the parameter settings for the LAS Dataset To Raster tool:
- Set the Value Field parameter to Intensity.
- Set the Interpolation Type parameter to Binning, Cell Assignment to Average, and Void Fill Method to Simple.
- Set the Sampling Type parameter to Cell Size.
- Set the Sampling Value parameter value relative to the point spacing of the data. A value of two to four times the average point spacing is reasonable.