[Talk-GB] (OT) Depressions, and projections

[Donald Allwright]

>(1) Can you think of any depressions in Britain?  I.e. places where the contour lines on the map would wind the "wrong way"?  I ask because I recently noticed that the OS OpenData contour data is wrong around Princes Street Gardens in Edinburgh.  It looks as if the contour lines are in the right places but their heights have been mis-labelled, as if the height labels had been added automatically by an algorithm that didn't expect depressions.  The gridded data is consistent with the incorrect labelling, probably confirming that the gridded data is derived from the contours, rather than vice-versa.  The only other depressions that I can think of are the sunken areas in the Fens.  Any other suggestions?


There are many depressions on a small scale in carboniferous limestone areas, where rivers/streams have disappeared underground or where caves have collapsed. I can think of a number but whether there are any that are large enough to show up in OS data is another question. Take a look here as an example:

http://www.openstreetmap.org/?lat=53.33172&lon=-1.83588&zoom=15&layers=C


You can see that there are a few strange things happening but the scale is not really large enough to be clear.

Donald
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