High resolution DEMs from unmanned aerial vehicles

Abstract

Demand for high resolution DEMs in Australia seems to be insatiable. Released in 2012, the national 1 second resolution (30m) DEMs derived from SRTM provided a consistent high resolution continental coverage, though there are always applications that require better resolution. This is particularly the case where river channels that are less than one grid cell in width are involved. Examples where channel shape is important include hydrodynamic modeling and dam siting. Previous papers by the authors at Modsim07 and Modsim09 described the need for more frequent survey with finer DEM resolution and the potential for cost effective methods such as Photosynth, which has since been joined by a number of commercial and open source competitors. A major obstacle in that method was the transformation from model to world coordinates. Recent developments in this area include the ability to work directly in world coordinates using air photos tagged with GPS camera position coordinates. Alongside software development has been the rapid development of low-cost and effective Unmanned Aerial Vehicles (UAVs) and cameras capable of obtaining high quality aerial photographs and video. The main advantages of these platforms are their relative low cost, less dependence on contractor schedules, and the flexibility to select the conditions and fly as frequently as necessary to achieve a desired result. This paper describes the methods used in setting up a UAV and obtaining air photos, together with the use of freely available Structure from Motion (SFM) software to derive a high resolution DEM to supplement the national 1″ DEM. Comparisons of DEMs with the 1″ DEM show the effectiveness of relatively modest inputs.