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Part of my map making workflow that uses OpenStreetMap (OSM) data requires updating the existing data set to be as accurately as possible before exporting the data. The data that I originally loaded into OpenStreetMap for River Bends was based on GPS surveying that I did not long after some new trails were built. Thus, the (prone to error) GPS data was the most accurate data available.
When updating OSM data, one is explicitly permitted to trace Bing imagery to enhance maps. Earlier today while poking around in JOSM (which adds Bing data as a tile so it can be traced) I noticed that the latest imagery for River Bends was taken on March 11, 2012 and most of the recently built single track is now visible. Because of the particularly wet spring here in Southeast Michigan many of the trails were muddy while these photos were taken, resulting in the trails being visible dark marks on the traceable photos.
The image above demonstrates this, showing the imagery date, current OSM data (red dashed line), and the wide/dark lines are the trails themselves. By adjusting the routes to match the imagery I can radically clarify the OSM data, validating and refining routes. River Bends is due for a map update soon after some new trail construction is complete, so this means that the next map of there will be much, much more detailed and accurate. Thanks in large part to a wet, muddy March.
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