Automatic Flight Planning for Unmanned Aerial
Vehicle Utilizing GIS Analysis on Digital Elevation
Model
Itthi Trisirisatayawong, Pannee Cheewinsiriwat
Geo-Image Technology Research Unit, Dept. of Survey Engineering
Chulalongkorn University, Bangkok 10330, Thailand
Tel: +66 (0)-2218-6654 Fax: +66 (0)-2218-6653
E-mail: itthi.t@eng.chula.ac.th,
pannee.ch@chula.ac.th
ABSTRACT
This paper describes a GIS-based application to plan image-acquisition mission of unmanned
aerial vehicle (UAV). Short range UAVs of up to 200 km operational distance are being
developed by various universities and the army’s artillery division under a joint research funded
by the Thailand Research Fund and the Ministry of Defence. The ultimate goal of UAV is to fly
to take images of target areas, particularly those along or over the border, using onboard video
camera. The acquired images will be mainly used for security purposes such as surveillance,
reconnaissance, military mapping or intelligence. The nature of this task is always risky. Though
UAVs require no human pilot aboard and thus incur no human loss, any loss of the aircraft is
still considerable. Avoiding such loss by flying UAVs further away from the target area, the
imaging mission may fail. Optimum flight path is therefore critically important to the success of
UAV mission. Flight parameters including altitude, aircraft position, look-angle and time must
be thoroughly and carefully pre-determined to ensure that the desired image will be taken while
aircraft safety is maintained. The computation of UAV positions and the image acquisition time
must also take into the account problems such as line-of-sight obstruction or hill shadow. As
part of the UAV research project, a software module for automatic flight planning has been
developed in a GIS environment to analyse digital elevation mode (DEM), sun angle and
azimuth, the aircraft capabilities and limitations in order to produce optimum flight parameters.
Logical block diagrams, procedures and results are detailed in the paper.
1. INTRODUCTION
Unmanned aerial vehicles (UAVs) are remotely piloted or self-piloted aircraft that carry
communication equipments and cameras, sensors, or other payloads. The advantages offered by
UAVs to civilian and military users are numerous, most notably in mission areas commonly
categorized as “the dull, the dirty, and the dangerous” (Office of the Secretary of Defense, 2002).
For example, due to its vintage point, one unmanned sentry equipped with automated cuing
algorithms and multiple sensors could survey the same area as ten or more human sentries (“the
dull”). UAVs could reconnoiter areas contaminated with radiological, chemical or biological
agents without risking human life (“the dirty”). Unmanned combat air vehicles could perform
the high-risk suppression of enemy air defenses missions currently flown by manned EA-6s or
F-16s (“the dangerous”).
An Israeli-built UAV system has been used in image intelligence task by the Thai army’s
artillery division for almost a decade. The proprietary system has proved to be useful but
upgrading and enhancement are difficult. The Research and Development of Unmanned Aerial
Vehicle project which is a 3-year collaboration between universities, air cadet school and the
defense ministry R&D unit started in June 2004 aims at building a modern system comprising a
few unmanned aircrafts, a payload unit and ground control station
For the Thai army, the most frequent UAV missions are “the dangerous” part, i.e. to take images
over sensitive or conflicted areas particularly along the border. Though no human loss will be
incurred, any loss of the aircraft is still considerable. The danger can be mitigated by flying
UAVs further away from the target area, but by doing so it may fail to take the desired images
and jeopardise the very objective of the mission. The optimum flight path is thus crucial to the
mission success.
Part of the research is to develop a GIS-based flight planning software module that will assist
mission planner to generate pre-determined flight data. Given the target position, airfield
position and mission date, the module will analyse topography and produce three dimensional
coordinates and time of aircraft positions along the suggested flight route. Capabilities of the
being-built UAVs such as operational range, maximum altitude and speed are taken into account
as well as the mechanical capabilities of the video camera. Factors concerning aircraft safety
such as restricted areas where the UAVs are not allowed to go in as well as minimum clearance
of the vehicle above the terrain are also needed in the analysis.
