As previously mentioned in diary entry http://www.openstreetmap.org/user/MikeN/diary/39782 , the MapRoulette Rail challenge uses topological analysis of the rail network to generate the task list. Many tasks land on a multi-track crossing or include a rail yard, so many tasks correct fix more than 1 crossing per edit session. Also, anyone routinely reviewing an area might correct rail crossings outside of MapRoulette By re-analyzing current OSM data, finished tasks were marked off. Some findings for the last interval:
- 1221 tasks marked complete in Map Roulette
- 5468 tasks auto-marked complete after detection as fixed
- 4.5:1 node correction per task ratio
- Overall topological rail challenge 16% complete 10925 / 68758 tasks
Because the first MapRoulette tasks are more likely to land on in a ‘busy’ area, future fix rates and node correction to task ratio will probably fall as each task is more likely to point to an isolated crossing.
Many tasks end up making geometric corrections to the rails and surrounding roads.
The links to these challenges are:
[Crossing Ways: Highway-Railway, US] http://maproulette.org/map/980
[Crossing Ways: Pedestrian-Railway, US] http://maproulette.org/map/989
[Crossing Type: Highway-Railway, US] http://maproulette.org/map/990
[Crossing Type: Pedestrian-Railway, US] http://maproulette.org/map/991
There was a moment of panic as the analysis also discovered thousands of new tasks! This had 2 causes:
- An abandoned rail line / cycle trail was changed to be a railway. I have commented on that changeset asking for more information.
- A node from changeset http://www.openstreetmap.org/changeset/43738090 was moved across the country near the following changeset http://www.openstreetmap.org/changeset/43738103 in JOSM. From a history examination, I’m not sure if the rail node was attached to Benton Street. Maybe there is a JOSM hotkey that does this. To try to avoid this in the future, I have changed MapRoulette to open JOSM in a new layer.