Dave Arquati wrote:
Aidan Stanger wrote:

Stephen Osborn wrote:

snip John Rowland wrote:

I think you are wrong there.

Contours mark places of equal height. If two contours touch at any one
point then, de definito, they have to touch at *all* points, so the two
contours become one contour.

You already have the counterexample of a vertical cliff. I have seen
those in nature - although not all of the cliff was vertical, there were
certainly parts that were, and they were definitely big and vertical
enough for contours to meet on the map.

I am still not convinced you will find a natural cliff that is *truly*
vertical (e.g. measured by a plumb line) for more than 10 metres, in
order to have the contour lines coincident.

I would be fascinated if you can think of an example where this is true.

For a travel map to be of use, every point on it has to share share the
same centre.


That statement is absolutely ridiculous!

Yes it is, isn't it. I had fallen into the same trap as Larry Lard (in
an earlier post) had and was thinking of the distance from the centre
showing the travelling time. Probably too much time looking at LU zonal
maps!

this would be referred to as isochromic isochrones!

Nice!

--

regards

Stephen