Effects of fog attenuation on LIDAR data in urban environment

Light Detection And Ranging (LIDAR) offers univocal means of data capturing in remote sensing. It can collect intensity and distance data during day and night alike, albeit with limitations in accuracy due to weather conditions. Owing to weather conditions, factors affecting the performance of LIDAR intensity data include rain, haze, fog and snow. The effect of weather is twofold: scattering by aerosol and absorption by the presence of water drops. The prime objective of this research is to investigate how fog conditions deteriorate the quality of LIDAR intensity data. Experiment is carried out using Velodyne HDL-64E with 905nm wavelength. For experiment fog is classified into stable fog type 1 and stable fog type 2 categories based on the International Visibility Code (IVC). Since, theoretical approaches based on microphysical models are very complex and time consuming; hence, atmospheric attenuation of laser beam is calculated using empirical model which is based on visibility range estimate. Analysis is performed in order to discuss the results with respect to the effect on intensity data. The experiment is carried out with various levels of fog to view the impact of water droplets concentration and size on the accuracy of LIDAR data. The results show that fog attenuates the LIDAR laser pulse drastically, resulting in low contrast image thus making it difficult to detect objects in the intensity data.