Using Photogrammetry to Determine the Position of a Fixed-wing Mini-UAV in Flight

Gosse Wedzinga, National Aerospace Laboratory NLR, Amsterdam, the Netherlands
René Ladiges, National Aerospace Laboratory NLR, Amsterdam, the Netherlands

Abstract

This paper addresses the problem of determining the position of a fixed-wing mini-UAV (Unmanned Aerial Vehicle) in flight, independently from the own position reported by the mini-UAV itself. This independent position can be used as reference position for validating the position provided by the mini-UAV.

A photogrammetry approach is presented for computing such a reference position from an image taken by a camera on-board the mini-UAV of points on the ground with known location. The approach uses the mathematical concept of triangulation in combination with the Gauss-Newton iterative algorithm for solving non-linear least squares problems.

Flight tests have been conducted whereby a mini-UAV is flown multiple times over a grid of marker points with known location. Images of the grid were recorded during each passage. After the flight, a set of suitable images was selected and for each image, the reference position of the mini-UAV has been computed and compared with the position reported by the mini-UAV itself.

It is concluded that the photogrammetry approach is indeed feasible and reference positions can be computed with an accuracy of several meters. Mini-UAV’s are quite sensitive to crosswind. This characteristic makes it somewhat difficult to control the flight of the mini-UAV directly over the grid in order to obtain images that are optimal for photogrammetry purposes. The main advantage of the method is that it only makes use of a camera that is already available on the mini-UAV; no additional equipment is required.