Intensity Based Range Corrections

Intensity is an important piece of information that is collected by laser scanner systems. The intensity value is the strength of the return pulse, or the amount of energy returning to the system. The intensity is influenced by a number of factors, including the reflectivity of the target, where, highly reflective targets, such as paint markings, result in a higher intensity return than low reflectivity targets, such as asphalt. This variability in the intensity is what allows for a pseudo black and white image to be generated from LIDAR data (Figure 2). With LIDAR data the intensity of the return can also have a significant effect on the elevation of the resulting discrete point. System manufacturers generally attempt to compensate for systematic range biases through the use of intensity tables, or intensity based range correction (IBRC) tables that are unique to each system. If these tables are not correct, or if the system is behaving in a manner contrary to the calibrated values then one will notice highly reflective objects appearing in the DEM (Figure 1) even when they should have relatively the same elevation as the surrounding surface. Typically paint markings, or highly reflective objects, will appear higher than the elevation of the asphalt surface.

Intensity Based Range Corrections

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