Assessment of the homogeneity of volunteered geographic information in South Africa

The potential for volunteer groups to contribute geographic data to National Mapping Agencies has been widely recognised. Several investigations have been done to determine the geometric accuracy of this data for the purposes of national mapping. Beyond accuracy, from a production perspective National Mapping Agencies will also be interested in...

Automatic object recognition and change detection of urban trees

Monitoring of tree objects is relevant in many current policy issues and relate to the quality of the public space, municipal urban green management, management fees for green areas or Kyoto protocol reporting and all have one thing in common: the need for an up to date tree database. This study, part of the Tree and Image research project,...

Improving 2D change detection by using available 3D data

Change detection with very high resolution imagery is difficult, because 3D objects as buildings appear differently in 2D imagery due to varying viewing angles and sun positions. This research proposes a method to improve change detection by using simple 3D models of buildings. Buildings have been modelled as flat roof or gable roof buildings....

Updating land-use information on topographic maps using satellite imagery : combining the advantages of two accessible sources of geographic information

This paper examines the possibilities of using Landsat Thematic Mapper images for updating land-use information on topographic maps. Information obtained from satellite images can be kept up-todate and a large number of classes can be distinguished. However, the quality of the information still leaves much to be desired, with a reliability of no...

The potential of combined use of satellite data with topographic information

Landsat Thematic Mapper, SPOT panchromatic and SPOT MSS imagery from 1986 were investigated for their capabilities of keeping topographic maps up to date. Topographic information was digitally combined with satellite data using raster techniques. From the map line-information on roads, naming-conventions, water and housing was used to cover a...