On-the-Fly Edge-Matching for Cascaded Service Content

Cascading download services combine various background services together so that their contents can be queried via a single service. A common problem with cascading services in a multinational setting is that the features coming from the services of different countries often do not match across border areas. Usually, edge-matching is executed iteratively as an off-line process between the neighbouring countries where adjustments and tests can be made during the matching process. On-the-fly edge-matching process is carried out during the service request and it leaves no room for modifications or negotiations. We present in this paper a method for performing on-the-fly edge-matching for linear features in a multinational cascading service environment. The proposed algorithm uses a country boundary lines data set and a connecting feature points data set that contains pre-determined locations on the boundary lines where the features should be matched. The results show that the proposed approach is suitable for most edge-matching situations where the connecting feature points are available. Problematic cases include situations, where the features are alternating across the border and cases where the features don’t reach near enough to the border line. In the proposed approach, the edge-matching is executed simply by moving selected line end points to the locations of connecting feature points. In future, the process could be improved by adopting conflation methods that produce visually smoother results and extending the edge-matching functionality to cover also polygonal features.