OpenStreetMap

Robert Whittaker has commented on the following diary entries

Post When Comment
Day 2 over 1 year ago

The Overpass API at http://overpass-api.de/ can be used to query the OSM database in lots of different ways. If you want to extract all the ways and nodes that make up the UK railway network, both past and present, then you'll probably want to find any ways tagged with railway=rail, disused, dismantled, abandoned, preserved, and possibly narrow_gauge too.

The Overpass Turbo service at http://overpass-turbo.eu/ can be used to test queries and get a quick visual output of the objects that the query returns. Something like the following may be what you want: http://tinyurl.com/bl2gawv (Once the page has loaded, adjust the map view as required, then click on "run" in the top left to get the results.)

Once you've got the output from the Overpass API, you'll need to convert the JSON or OSM XML data into the format (eg GPX) that you want.

Of course, there may well be gaps in the disused railway network in OSM. Opinion is divided on whether or not we should store old railway routes which are no longer visible on the ground. Some people suggest using railway=dismantled for this, rather than disused or abandoned.

If you want to extract specific old lines automatically, then they would need tagging in some way to identify them. Again it is debatable whether this is appropriate, given that the OSM database is primarily there to record the current situation. However, it may be permissible to tag former railways with something like former_operator=* or former_line=*. Alternatively, one could create route relations for former lines, mirroring the relations used for current lines, e.g. http://www.openstreetmap.org/browse/relation/138808 . (For more information about relations, see http://wiki.openstreetmap.org/wiki/Relation .) But please discuss what you plan to do on the talk-gb mailing list before going ahead.

University of Cambridge map now live almost 2 years ago

This looks great. Would I be right in thinking that the map data being used is a snapshot taken from OSM at some point in time?

Are they using the raw OSM data (possibly with some transformations before rendering) or did any manual edits need to be made outside OSM? How is it planned to mange merging in future changes that occur in OSM?