[Proj] Extended range TM usage

Clifford J Mugnier cjmce at lsu.edu
Tue Aug 26 12:14:37 EDT 2008

The most common rational reasons include GIS applications of hydrocarbon-producing regions.  For example, the entire Gulf of Mexico, significant portions of Siberia, the Persian Gulf, etc.  The key word is "region."  There are numerous cartographic uses for this in Reservoir Engineering as well as maintenance of lease blocks data bases, etc.
The military has ALWAYS recognized this need and actually published a special book on Zone-to-Zone transformations.
I seem to write about these valid rational reasons periodically, and I think I do so in this discussion list.
If you don't want to implement this sort of thing and are looking for a reason not to do so, use sunrise tomorrow as an excuse.
Cliff Mugnier


From: proj-bounces at lists.maptools.org on behalf of support.mn at elisanet.fi
Sent: Tue 26-Aug-08 07:35
To: PROJ.4 and general Projections Discussions; geraldi.evenden at gmail.com
Subject: Re: [Proj] Extended range TM usage

"Gerald I. Evenden" <geraldi.evenden at gmail.com> wrote:

> My question is can anyone supply a rational reason for the practical use of an
> elliptical TM projection with extended longitude range.

How practical is that, I don't know, but there is the situation where an user
is zooming out a view so much that a very large area is visible. There can rise
a situation where those extreme areas should be shown somehow. The
accuracy does not matter in that case, since it is only show in relation with
that middle section which is the main focus.

This same situation applies basicly to all projections. Sometimes users zoom
out the views very much and the extreme areas should be shown somehow.
Sometimes clipping them away, or projecting to some limiting line, might be
as good alternative. But my opinion is that it is better to show something than
nothing even if it is a bit unaccurate.

If somebody wants to have more aggressive limiting, he might use the error
mechanism, where the library warns him about the error getting too large
and that particular solution might start to clip those areas away.

Regards: Janne

Proj mailing list
Proj at lists.maptools.org

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.maptools.org/pipermail/proj/attachments/20080826/11dc660a/attachment.html

More information about the Proj mailing list