These methods are useful to detect underground hollow spaces but they provide limited information about spatial details with low levels of accuracy. Image-based photogrammetric surveying can also be used in cave studies but the difficulty of achieving homogeneous light conditions is a limiting factor

<p><strong>Abstract.</strong> High-resolution solar radiation modelling requires the three-dimensional geometric structure of the landscape to be respected. Currently, remote sensing methods such as laser scanning and close-range photogrammetry are most commonly used for detailed mapping. The output is detailed 3D models containing buildings, trees, relief and other landscape features. The raster approach allows modeling solar energy for relief, but it is unsuitable for landscape objects such as buildings and trees. The polygonal features vector approach is mainly designed for buildings. Our goal is to create a freely available tool for highly detailed solar radiation modelling for geometrically complex 3D landscape objects. In the paper, we present a prototype of the v3.sun module. We propose a solution of solar radiation modeling designed for all landscape features based on TIN data structure. In the paper, tests of the proposed algorithmic solution for various types of 3D data obtained from the above-mentioned collection methods are demonstrated.</p>

The calibration of the light detection and ranging (LiDAR) system is critical to ensure the accuracy of point data. In this paper, the lever-arm measurement of airborne LiDAR system (ALS) was realized by photogrammetry. An automatic iterative boresight calibration method based on approximate corresponding points (CPs) matching was proposed to correct the boresight misalignment. It was based on iterative closest point (ICP) registration algorithm with a normal space sampling strategy, and approximate CPs were obtained by establishing filter rules. The experimental results showed that the absolute accuracy of the calibrated ALS reached 7.13 cm when the flight altitude was 100 m, meeting the accuracy requirements.