As Britain’s national mapping agency, one of our main tasks is to keep our mapping and spatial data as up to date as possible. To ensure this, we need to know when new houses have been built, when sites have been re-developed, and when any other changes have occurred which will affect our mapping. We obtain information about change from many sources, including local authorities, surveyors on the ground, and from aerial photography.
Detecting the changes from aerial photography is a skilled, yet laborious and time-consuming manual process, in which a team of people compare the aerial images with the features in our mapping. We would like to make this a more automated process.
Extracting change information from aerial photography
Our change detection research team has investigated several methods of detecting change and is now concentrating on the most promising – using object-based image classification techniques. This process uses digital aerial photography, together with the height data derived from it via photogrammetry, to identify the features we are most interested in. These are then compared with the corresponding features in our OS MasterMap® database. This automatic process identifies new features, features which are no longer present, and any changes to significant features.
Following a number of trials in our production area, we are confident that we can now automatically detect changes to topographic features - including demolished and significantly altered buildings, areas of vegetation, water features, and changes to communication networks – to a degree of accuracy comparable to that of the manual process. Work is underway to fully utilise these techniques within our topographic data capture flowlines.
For more information:
Contact: Anne Patrick, Research Project Coordinator