[mapserver-users] project onto a globe?

[Ed McNierney]

Tom -

The biggest distinction is whether you're trying to display a hemisphere or the entire Earth.  If you look at a globe, you only see half the Earth at one time, whereas the sample map you pointed to shows the entire Earth at once.

Projections that show only a hemisphere at a time are much more commmon and more "natural" - the Orthographic (mentioned below) and the Lambert Azimuthal Equal-Area are popular.  The Orthographic is the one that most resembles a globe - it's actually what a globe would look like if viewed from an "infinite" distance.  It is especially nice when used in its oblique form, where the center point is neither on the equator nor at the poles.

Just remember that this will only provide half the Earth at a time, just like a real globe does.

	- Ed

-----Original Message-----
From: Tom Hodder [mailto:t.hodder at globalgold.co.uk]
Sent: Tuesday, November 26, 2002 2:22 PM
To: Mapserver-Users at Lists. Gis. Umn. Edu
Subject: RE: [mapserver-users] project onto a globe?



>If I understand correctly, what you folks in the UK call a "2D
representation of a globe" is known as a "circle" over here
><g>.

;-)

>
> Tom -
> Do you mean that you want the image to look like a globe?  If so, you need
> to use an orthographic projection.  By virtue of making an image, you are
> doing some kind of projection from the earth to the plane of the image.
>
>

This is pretty much what I am trying to achieve.

I've only starting reading about
this stuff in the last couple of days so I'm missing chunks of information
that are probably quite basic for experienced mappers.

>You'll have to give us a little more information. MapServer supports a HUGE
>array of map projections through PROJ4 ... so, yes, you can do it.
>
>See http://mapserver.gis.umn.edu/doc36/coordinates.html

i going to read this thoroughly and see if  what I can do with it.

Thanks for the help so far.

Tom