Adaptable Flight Line Planning for Airborne Photogrammetry Using DEM

Flight line planning is the first step in an aerial photography campaign. Its two key parameters, ground sampling distance (GSD), and overlap should be designed carefully as they will impact subsequent flying workload and even the final mapping accuracy. For a flat terrain region, flight line planning is easy using a traditional method with fixed baseline, flight spacing, and flight altitude. But for a steep terrain region, photo overlap and GSD will change greatly with topography, and thus a flight line planning using the traditional method is not sufficient. This article presents a novel adaptable flight line planning method for frame camera with four application modes. The flight line planning procedure is implemented through rigorous imaging geometry model using digital elevation data, where actual overlap and GSD can be calculated precisely. Using the desired overlap and GSD as constraint conditions, the flight spacing, baseline, and flight altitude can be adjusted adaptively according to ground topography. To assess the effect, a hypothetical test in a rugged terrain region was conducted to compare the project workload, GSD, and overlap of the four modes. The results show that Mode 2, Mode 3, and Mode 4 can realize better overlap with lower workload than the traditional method Mode 1. Mode 3 and Mode 4 have better GSD distribution than Mode 1 and Mode 2. The Mode 3 method was also validated in an actual project, showing a favorable performance in final reality 3D model result.