A METHOD FOR DETERMINING THE COORDINATES OF UNMANNED AERIAL VEHICLES IN THE ABSENCE OF GPS SIGNALS

Abstract

Multirotor unmanned aerial vehicles (UAVs) are widely used nowadays in various military and civil areas, including rescue operations, finding the fires in forests, monitoring of the road conditions, and many others. The UAV’s flight along the required trajectories is performed using the GPS signals which determine the vehicle’s position with sufficiently high accuracy (from tens of centimeters to few meters). But, in practice, some situations may occur when the GPS signals are absent or corrupted. In such cases, an important task is determining the current coordinates of the UAV, which is necessary for determining the coordinates of the ground-based objects that are being tracked from the UAV.

In the paper, an approach to determining the geodetic coordinates of the UAV is proposed in cases when the GPS signals are absent, but the coordinates of two ground-based, the so-called reference objects, are known. As reference objects, the ones that are distinguished within the local terrain and can be easily identified are selected, for example, separate buildings, relay broadcasting pillars, power transmission line supports, etc. The hardware of the system of determining the UAV’s coordinates in the absence of GPS signals consists of two sets of video cameras with laser rangers which are mounted on the body of the UAV in two-axis Cardan gimbals. Each camera is directed at the corresponding reference object on the Earth’s surface, and after that operation, the axes of Cardan gimbals are fixed. Calculation of the current coordinates of the UAV is performed based on the known coordinates of reference objects, distances of those objects to the UAV (signals from laser rangers), as well as the height of the UAV above the Earth’ surface. The algorithm of numerical determining the UAV’s coordinates in MATLAB language is presented.