From: "Frank J. Øynes" <frank@spacetec.no>
Newsgroups: comp.graphics.algorithms
Subject: Re: Mercator Projection
Date: Mon, 18 Mar 1996 17:09:42 +0100

Tim Dierks wrote:
> 
> Does anyone have an algorithm to do a Mercator projection?  I need to
> convert a map of the world that is specified as a collection of latitude
> / longitude points to an x / y coordinate system.
> 
> Thanks.
> 
> Tim Dierks

Have a look at http://www.gisnet.com/gis/ores/gis/data.html
for a list of available tools.

I, on the other hand, would go directly to 
ftp://kai.er.usgs.gov/pub/PROJ.4
(check ftp://kai.er.usgs.gov/pub/PROJ.4/README first)
and pick up proj4 documentation and software. 

It is, IMHO, one
of the most well-documented and well written PD software packages
available for doing exactly what you request.
It's written in POSIX compliant ANSI C by Gerald I. Evenden, and has
probably support for all the map projections you will ever need -
and creating a program for your need would require less than 10 lines
of code using his library.

Frank.
-- 
/* Frank J. Øynes        |              frank@spacetec.no               /*
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==============================================================================

From: jfw@radix.net (Jim Ward)
Newsgroups: comp.graphics.algorithms
Subject: Re: Mercator Projection
Date: Tue, 19 Mar 1996 01:39:50 GMT

>There's a Gem in the first Graphics Gems book, on pages 307-320 that lists
>transformations for various cartographic projections. The Mercator projection
>yields equations that involve the Gudermannian function. Does anyone know 
>what that is?

From  a math book I have:

    gd(x) = arcsin(tanh(x)) = arccos(sech(x)) = arctan(sinh(x))

==============================================================================

Newsgroups: comp.graphics.algorithms
From: kleiner@taurus.harvard.edu (Steve Kleiner)
Subject: Re: Mercator Projection
Date: Tue, 19 Mar 1996 15:22:04 GMT

Tim Dierks (tdierks@cts.com) wrote:
: Does anyone have an algorithm to do a Mercator projection?  I need to 
: convert a map of the world that is specified as a collection of latitude 
: / longitude points to an x / y coordinate system.

: Thanks.

: Tim Dierks


look at 

   http://fits.cv.nrao.edu/documents/wcs/wcs.html

This page describes the map projections used by the Flexible
Image Transport System (FITS) developed for the astronomical community
at the National Radio Astronomy Observatory. 

Contents include:

wcs.all.ps (520 KB) -- The draft proposal for "World Coordinate System"
syntax in FITS headers. The figures and the mathematics in this
paper are impressive.  

Talk94.ps (121 KB) -- Textual view graphs describing the draft proposal 
for "World Coordinate System" syntax in FITS headers.  

Poster94.ps (50 KB) -- Graphical view graphs describing the draft 
proposal for "World Coordinate System" syntax in FITS headers.  

USGS-90-284: USGS document "Cartographic Projection Procedures for the UNIX
Environment -- A User's Manual" -- page 0 -- pages 1-16 -- pages
17-32 -- pages 33-48 -- pages 49-63, contents 

AIPS Memo #27 (168 KB, PostScript) -- the 1983 AIPS WCS document 

--
Steve Kleiner    skleiner@cfa.harvard.edu