IMPROVED METHODOLOGIES FOR THE REVISION OF A TRADITIONAL TOPOGRAPHIC MAP SERIES
- 1University of Porto, Science Faculty, Rua Campo Alegre, 416-007 Porto, Portugal
- 2Academia Militar, Rua Gomes Freire 203, 1169-203 Lisboa, Portugal
Keywords: Direct georeferencing, Topographic mapping, orthomosaic, DSM, change detection
Abstract. Conventional topographic maps are still important for many applications, such as land planning, but require frequent updates, which involve high costs and are not easy to accomplish. There are however many advances in Photogrammetry that are not always exploited to their full potential in a real map production environment. The traditional process involves aerial triangulation with ground control points, stereo restitution in digital photogrammetric workstations and field completion. The process is very time-consuming and expensive and map update is many times not done with the frequency required by users.
This paper describes the implementation of an improved methodology for very frequent revision of the Portuguese map series of scale 1:25,000 making use of conventional digital aerial photography, which now is acquired on a regular basis for all the country. Vector features are digitised in monoscopic mode, in a GIS environment, over true orthophotos. These can be produced in a largely automated manner, using direct georeferencing data, and with minimal ground control only for vertical adjustments. Revision time and cost can be significantly reduced, keeping acceptable accuracy standards. That will satisfy the users that require the traditional high standards of the topographic map series for land panning.
Additionally, for the task of field data collection of information that cannot be obtained from aerial photographs, a method is being applied to make use of video data collected in the field along roads with action cameras, with GPS. Operators can confirm or identify attributes of objects along, or near roads, such as power lines.