Intensity correction of multi-return signal from airborne laser scanning to improve land cover interpretation

Airborne laser scanning technology is widely used in photogrammetry and remote sensing, enabling three-dimensional information about objects located on the Earth’s surface to be obtained. In addition, the intensity of the reflected signal is received, which records the power with which the laser beam is reflected from objects. Moreover, unique to laser scanning is its ability to penetrate vegetation. As a result, more than one return may be acquired for a laser beam regarding vegetation. With each return, there is a loss of laser beam power, which can be problematic when classifying and interpreting land cover under trees, especially in urban areas. This article presents a methodology for correcting the intensity values of multiple returns on the ground to improve the interpretation of land cover under trees. For this purpose, methods for calculating transmittance and methods based on the Beer-Lambert law were examined. The effectiveness of the developed methodology was evaluated through statistical analyses and intensity images before and after correction were generated. The results of the studies showed that it is possible to effectively correct the intensity of signal multiple returns, thus improving the interpretation of land cover under trees. The accuracy of intensity image classification before and after intensity correction improved from 0.57 to 0.79 in the leaf-on season and from 0.44 to 0.62 in the leaf-off season.