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Airborne laser scanning (ALS) is widely used passive remote sensing technique. The radiometric calibration of ALS data is presented in this article. This process is a necessary element in data processing since it eliminates the influence of the external factors on the obtained values of radiometric features such as range and incidence angle. The datasets were captured with three different laser scanners; since each of these operates at a different wavelength (532, 1064 and 1550 nm) this makes the experiment more interesting. Radiometric calibration is a complex process, and a short theoretical background is therefore provided at the beginning of the article. The applied calibration procedure relies on areas with known reflectivity. The calibration regions should exhibit stable radiometric properties, therefore asphalt is used to calibrate each dataset and calculate a calibration constant for each flight block (wavelength) independently. Following this, the results of radiometric calibration, reflectance and backscattering coefficient, are presented and discussed in detail. Finally, the obtained reflectance values are compared with spectral characteristics. It could be shown that the reflectance values which result from radiometric calibration are similar to values presented on spectral characteristics.
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