[Proj] Little sphere projection

support.mn at elisanet.fi support.mn at elisanet.fi
Mon Aug 8 03:55:21 EST 2011


I am not sure, but it does not sound that your problem is projection
related since in small scale changing the projection does not add
anything too much to the result since almost all normal projections
give similar results when the curvature of the earth does not affect
very much the end result compared to the planar representation of

The projection starts to play role for example near poles when you
are using for example Mercator projection. The distortion of the
plane representation of the earth is so huge that the projection is
no more usable and it gives wrong results. But in most normal
cases where maps are made with fair accuracy there should not
be any need to change the original projection.

You can draw spheres or what ever on all normal maps using
normal local projections and the results should be rather accurate.

Regards: Janne.


"Carlo A. Bertelli (Charta s.r.l.)" [carlo.bertelli at gmail.com] kirjoitti: 
> Hello,
> I'm trying a simplistic approach to a topological representation. I'm
> mapping the possessions belonging to a group of abbeys in a regional
> space. Il works well at a small scale, but when the abbeys are
> clustered in major towns, the representation ties properties to the
> cluster and not to the single abbey. The fact is that towns (and
> clustering) play a significant role in this story (yes this happens in
> the 18th century), asks for a better representation.
> My idea is analysing each town cluster using a little sphere (or
> ellipsoid) centered on the town whith an emisphere that only covers
> the space of the region, so to show larger distances in town (so to
> distinguish any abbey) and reduced distances far from the town center.
> I think it should not be impossible to craft ad hoc projections, but I
> have no idea on how to do it. Could someone help me?
> c
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