Consideration of laser pulse fluctuations and automatic gain control in radiometric calibration of airborne laser scanning data

Abstract

ALS has become a standard tool for high-resolution topographic mapping within the last two decades. Besides the geometric data in form of three-dimensional point clouds, also radiometric information is available in form of amplitude and width of the backscattered echo (the latter is provided by full waveform (FWF) systems only). However, these radiometric observables need to be calibrated. Influences originate not only from the factors included in the radar equation, but also from fluctuations of the emitted laser pulse and from automatic gain control (AGC) devices. These two influences are investigated in detail in this study on behalf of the two data sets acquired with a FWF capable Riegl LMS-Q560 system and a Leica ALS50-II discrete echo system. It could be shown that the influences of laser pulse fluctuations and AGC can be removed to a certain extent. This way, radiometric calibration can be performed more reliably.