[Talk-GB] mapping tunnels
Michael Collinson
mike at ayeltd.biz
Fri Sep 28 08:39:45 BST 2007
At 12:19 AM 9/28/2007, Thom Shannon wrote:
>Does anyone have any suggestions how to map a long tunnel? I know how to
>tag the ways, the issue is where does the tunnel go. You can't exactly
>get a GPS trace! I want to map the tunnels under the Mersey. The
>queensway tunnel has 3 exits, all at slightly odd angles and there is a
>junction in the middle of the tunnel.
>
>Do you think I could figure out some reasonable positions using a cars
>odometer and a compass? Or does it not really matter that much?
>
>Another option just occurred, the tunnel was started in 1925, so any
>maps from that era would be out of copyright. Perhaps a trip to the
>library?
I feel that completeness of main features is more important than
accuracy in these early days of OSM. I therefore simply join the
tunnel mouths with as few nodes as possible (so that no one gets the
idea I have a mysterious source of information) and mark the tunnel
way source=interpolation. I sometimes place minimum nodes between
the tunnel mouths if there is an obvious curve and if there are
internal junctions on a best effort basis.
Of course in the longer term better accuracy would be good,
out-of-copyright maps would be your best bet I think. From
experience in my UK home town, you may also find a local history
museum or historian with a town planning map from the twenties - the
features may, of course, not have been built or may have been
adjusted but such maps were more widely distributed than actual
engineering plans.
Mike
Stockholm
[and Otley - Centre of the Known & Unknown Universe]
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