[OSM-talk] Mapping and surveying long road tunnels

Steve Chilton S.L.Chilton at mdx.ac.uk
Thu Mar 22 13:59:48 GMT 2007


Last weekend I went to the Open Knowledge Foundation OpenGeodata session
in East London (UK), and whilst there took the opportunity to map a
little around there, including Limehouse Basin. It struck me that we
haven't yet captured the Limehouse Link which is a mile long tunnel
opened in 1993 to make the Docklands regeneration area more accessible,
and curves gracefully right UNDER the Limehouse Basin. Whilst writing up
the session for the Society of Cartographers Newsletter, I started
musing on how the various mapping sites/agencies cope with showing the
Limehouse Link. The Ordnance Survey are fine, as are Multimap and
Streetmap (which both use proprietary UK mapping, from I think the same
source). However, Google Maps, Map24, Yahoo and Maporama - which are
mapping "remotely" - have more of a problem. Yahoo uses Navteq/TeleAtlas
data and compromises by showing the Basin as smaller and implying that
the link skirts the North side of it above ground. Map24 does the same
thing, with a different style and symbolisation, as does Maporama. Live
Local takes the Navteq data (showing the basin wrongly) and then
symbolises the link as underground, with dashed lines. And if you want
to see some really shoddy cartography then go in to max zoom in Live
Local! However, the best of all is Google, which has it splendidly
shooting across the basin, with no indication that it is underground.
See:
http://maps.google.com/?ie=UTF8&z=16&ll=51.511093,-0.036156&spn=0.008507
,0.015063&om=1
So could OSM do better? Well, leaving aside the fact that the Mapnik
layer doesn't yet have tunnels sorted, I am not sure it could. On the
Osmarender layer the nearby Rotherhithe tunnel is shown as a dashed line
but is a straight line connecting the roads N and S of the river. From
memory, the tunnel is in two bores, and curves in some kind of S shape
and I think the bores separate from each other significantly. The
Blackwall tunnel just east of here is not yet depicted, and the road
stops just by the Millenium Dome to south, and also to the north of the
river. But my actually point is, how can we get an accurate alignment
for tunnels such as this? How would you survey the curving underground
alignment of the Limehouse Link? I suspect even the best GPS handheld
devices won't get a signal. You can't get any useful data from the Yahoo
satelite imagery. You can't use any published map sources that you
consider reliable as it is too new for o-o-cop maps. 
Any thoughts?

Cheers
STEVE

Steve Chilton, Learning Support Fellow
Learning and Technical Support Unit Manager
School of Health and Social Sciences
Middlesex University
phone/fax: 020 8411 5355
email: steve8 at mdx.ac.uk

Chair of the Society of Cartographers:
http://www.soc.org.uk/
Mind the (Map) Gap:
http://news.bbc.co.uk/1/hi/magazine/5413010.stm




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