Abstract:
Unmanned Aerial Vehicles (UAVs) are increasingly involved in surveying work, becoming a reliable basis for information on three-dimensional terrain features. Until now, ground reference points have been used to provide reliable planimetric evidence for measurements from drones. Their placement and coordinates measurement takes quite a long time, which increases proportionally to the area under study. In addition, the use of these marks produces model distortions (especially over large areas of 1 sq. km or more), which then lead to the appearance of areas of local depressions and uplifts where they are not present in the terrain. These distortions arise due to camera position optimization error minimization algorithms and cannot be corrected. Refusing to use ground control points leads to other geometric distortions associated with characteristics of survey system lenses mounted on UAVs (so-called "saddle-shaped" models). This paper presents the results of high-precision digital elevation models creation using built-in UAV global Navigation Satellite System (gNSS) receivers. The methodology has been tested at ten sites in the Zakamye region of the Republic of Tatarstan (Russia) with an area ranging from 4 to 58 hectares. Correction of gNSS rover position was performed in post-processing from a virtual base station network located at a 6 to 70 km range from the surveyed sites. For all objects, DEM errors did not exceed 0.05 m on axes X, y, and Z. At the same time, the dependence of the error value on the study area size was not revealed. The received results of the analysis of errors can indicate the prospect of the use of low-cost gNSS-UAVs without the necessity of organizing a network of ground reference points, being limited only to the necessity of installing control points will repeatedly reduce the time of the field works, in particular on hardly accessible objects.
