TransDEM Forum

Wonder how accurate this is? As an experiment, I tried extracting part of the old Balkan route that ran down to the coast at Dubrovnik. I previously tried this with the Poehali maps but these were really out. Open Street is the only TMS/WMS which shows the course of the abandoned railway but on doing the extraction into Trainz the mapping was off by a considerable amount. Several sections of water were displaying halfway up the adjacent hillside. I know it is possible to "nudge" the DEM to compensate for this - if you know exactly how much offset is required on each axis - but I had hoped Open Street Mapping would be seamless on top of the DEM.

Open Street Map (OSM) is only as accurate as the data source used.

Usually all OSM features carry a revision history. If you enter edit mode at the OSM web site you mind be able to find out what the source and who the author was. (Not absolutely sure about on-line edit options here, off-line editing with JOSM will definitely reveal those secrets.)