Optimization of UAV Flight Missions in Steep Terrain

Klemen Kozmus Trajkovski,Dušan Petrovič,Dejan Grigillo

doi:10.3390/rs12081293

Klemen Kozmus Trajkovski, Dušan Petrovič + Show 1 more

Open Access

https://doi.org/10.3390/rs12081293

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Abstract

Unmanned aerial vehicle (UAV) photogrammetry is one of the most effective methods for capturing a terrain in smaller areas. Capturing a steep terrain is more complex than capturing a flat terrain. To fly a mission in steep rugged terrain, a ground control station with a terrain following mode is required, and a quality digital elevation model (DEM) of the terrain is needed. The methods and results of capturing such terrain were analyzed as part of the Belca rockfall surveys. In addition to the national digital terrain model (NDTM), two customized DEMs were developed to optimize the photogrammetric survey of the steep terrain with oblique images. Flight heights and slant distances between camera projection centers and terrain are analyzed in the article. Some issues were identified and discussed, namely the vertical images in steep slopes and the steady decrease of UAV heights above ground level (AGL) with the increase of height above take-off (ATO) at 6%-8% rate. To compensate for the latter issue, the custom DEMs and NDTM were tilted. Based on our experience, the proposed optimal method for capturing the steep terrain is a combination of vertical and oblique UAV images.

Highlights

Many mountains in the world consist of sedimentary rocks such as limestone, dolomite, flysch, conglomerates, sandstone or even combinations of these rocks and molds
If potentially unstable areas are sufficiently close to populated areas or if the amount of broken or cracked material is large enough to reach populated areas either in the form of debris flows, rockfalls, landslides or mudflows, they may cause significant damage to facilities, infrastructure, forests or agricultural crops
The custom digital elevation model (DEM) modify the actual digital terrain models (DTM) in a way that allows more consistent Unmanned aerial vehicle (UAV) distances from the terrain when used for mission planning

Summary

Introduction

Many mountains in the world consist of sedimentary rocks such as limestone, dolomite, flysch, conglomerates, sandstone or even combinations of these rocks and molds. The main parameters in flight planning for UAVs are the definition of the area of interest, selection of the flight altitude above ground level (AGL), flight speed, forward and side overlap of successive images and parameters of the digital camera (sensor dimension, pixel resolution and focal length). All these parameters influence the ground sampling distance (GSD) of the images as well as the accuracy of the final results [7]. The custom DEMs modify the actual DTM in a way that allows more consistent UAV distances from the terrain when used for mission planning. With a RceomnostetaSnents.i2m02a0g, 1e2,b1a2s93e, the overlap was reduced to 60% at the half of the height AGL and fu6rothf 2e0r reduced to 20% for a quarter of the height AGL

Development of Custom DEMs

The Fake DEM

The tilted DEMs

Findings

Nov 2018 4 Dec 2018 11 Dec 2018