[Proj] Question about authorship

Gerald Evenden gerald.evenden at verizon.net
Fri Mar 4 09:33:47 EST 2005

When mentioning EPSG, I presume we're talking about the #7 manual?

Just discussing Mercator I have problems with terms like "natural  
If there is a "natural origin" for Mercator it is the equator.  The  
origin can
be artificially shifted to any latitude with +lat_0.  This should not  
be confused with
+lat_ts= which a method of referring to "latitude of true scale."   
assumes that the user expects the scale (h=k) is unity at that latitude.
+lat_ts is used as an alternative to +k_0 which refers to the scale
at the equator.  +k_0 is primarily uses where +lat_ts is not appropriate
such as Transverse Mercator.  I think it is inappropriate to combine
specifying +lat_ts and +k_0 to be used simultaneously.

In Mercator (1SP) the description interprets Mercator as a limiting
condition for Lambert Conformal Conic.  In theory true but often
following such a development often to math that falls apart.
Mercator is usually developed on its base definition and not a
limiting condition for a cone.

What really caught my eye with this stuff is the two entries for
Mercator: (1SP) and (2SP).  C'mon.

Lastly, Mercator is dismissed a a projection.  This may be true with
regard to grid systems but certainly not true for navigational purposed.
Because of it properties it is still widely used for navigation charts

I can obviously refer to EPSG #7 and I am aware of PROJ.4 usage but I
am handicapped with details of GeoTIFF and others.
On Mar 4, 2005, at 12:43 AM, Frank Warmerdam wrote:

> On Fri, 04 Mar 2005 00:28:11 -0500, Gerald Evenden
> <gerald.evenden at verizon.net> wrote:
>> On an idle evening I examined the contents of the web site
>> http://www.remotesensing.org/geotiff/proj_list/
>> and had a difficult time deciphering some descriptions as well as
>> 	...

> Gerald,
> The "notes" sections are mostly pulled from the EPSG
> database, which I believe we both agree is not really
> a great source of detailed information on projections.
> I am happy to have updates to the information, but the
> main role of the pages is to indicate how a variety of
> reasonably common projections are described in different
> environments (EPSG, GeoTIFF, PROJ.4 and OGC WKT).
> Best regards,
> --------------------------------------- 
> +--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam,  
> warmerdam at pobox.com
> 	..

> _____________________________________
Jerry and the low riders: Daisy Mae and Joshua.
"The whole religious complexion of the modern world is due to the
absence from Jerusalem of a lunatic asylum." Havelock Ellis, 1914

More information about the Proj mailing list