[Proj] Standard projection for Mediterranean basin

Mon Feb 15 15:52:03 EST 2010

Agreed.  

My point was the gentleman originally was looking for appropriate "standard" parameters for the Mediterranean region.  The old WWII Grid has such parameters albeit for a conformal projection.  Adopting a spherical projection of choice, the old parameters give a "standard" treatment for the region.  Whether it's Albers Equal Area, Lambert Equal Area, or whatever, the primary question regarding choice of parameters was answered.

Since the purpose was to choose (presumably "standard" conic) parameters for a region, the choice of a False Origin is immaterial, including where one chooses a central meridian.  

If someone has an even older set of "standard" parameters for the Mediterranean region, have at it.  Betcha it's conic or close to it like a Bonne.  Anybody want Napoleon's parameters ???  I think I published it in one of my old columns on the Levant.

I believe the horse might finally be dead.

Clifford J. Mugnier, C.P., C.M.S.
Past National Director (2006-2008),
Photogrammetric Applications Division
American Society for Photogrammetry and Remote Sensing 
and 
Chief of Geodesy,
Center for GeoInformatics
Department of Civil Engineering 
Patrick F. Taylor Hall 3223A
LOUISIANA STATE UNIVERSITY 
Baton Rouge, LA  70803
Voice and Facsimile:  (225) 578-8536 [Academic] 
Voice and Facsimile:  (225) 578-8925 [Research] 
Honorary Life Member of the 
Louisiana Society of Professional Surveyors 
Member Emeritus of the ASPRS 
Member of the Americas Petroleum Survey Group
======================================================
http://www.asprs.org/resources/GRIDS/
======================================================

________________________________

From: proj-bounces at lists.maptools.org on behalf of strebe
Sent: Mon 15-Feb-10 14:04
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] Standard projection for Mediterranean basin

I do not understand Dr. Mugnier's response. Using the authalic latitude does not yield an equal-area projection if you project using a conformal projection. I cannot think of any use for mixing authalic latitude with conformal projection.

The purpose of the authalic latitude is to provide an equal-area projection of the ellipsoid onto the sphere. From there you may project to the plane using any spherical equal-area projection, yielding an equal-area projection of the ellipsoid onto the plane. While this technique will not preserve other properties of the spherical projection (such as standard parallels or constant scale along some meridian or somesuch), at least it drastically increases the available projections for ellipsoidal use.

I have, by the way, formulæ somewhere that I derived for computing the optimal standard parallels for Albers given the north/south extents of the map. I will post them if I happen to find them. The 1/6th rule would be fine for any real use, of course. The optimal is more of academic interest.

Regards,
- daan Strebe

On Feb 15, 2010, at 9:31:45 AM, "Jan Hartmann" <j.l.h.hartmann at uva.nl> wrote:

From:	 "Jan Hartmann" <j.l.h.hartmann at uva.nl>	
Subject:	 Re: [Proj] Standard projection for Mediterranean basin	
Date:	 February 15, 2010 9:31:45 AM PST	
To:	 "PROJ.4 and general Projections Discussions" <proj at lists.maptools.org>	
	Could you explain the relationship between Authalic Latitude and Equal Area projections? There is an article by John Snyder athttp://www.jstor.org/stable/2562645?seq=1, but it's a bit above my mathematical head.

	Jan

	On 15-2-2010 18:01, Clifford J Mugnier wrote: 

		So?

		Keep the parameters and just use Authalic Latitude.

		Easy.

		Clifford J. Mugnier, C.P., C.M.S.
		Past National Director (2006-2008),
		Photogrammetric Applications Division
		American Society for Photogrammetry and Remote Sensing 
		and 
		Chief of Geodesy,
		Center for GeoInformatics
		Department of Civil Engineering 
		Patrick F. Taylor Hall 3223A
		LOUISIANA STATE UNIVERSITY 
		Baton Rouge, LA  70803
		Voice and Facsimile:  (225) 578-8536 [Academic] 
		Voice and Facsimile:  (225) 578-8925 [Research] 
		Honorary Life Member of the 
		Louisiana Society of Professional Surveyors 
		Member Emeritus of the ASPRS 
		Member of the Americas Petroleum Survey Group
		======================================================
		http://www.asprs.org/resources/GRIDS/
		======================================================

________________________________

		From: proj-bounces at lists.maptools.org on behalf of Gerald I. Evenden
		Sent: Mon 15-Feb-10 08:30
		To: PROJ.4 and general Projections Discussions
		Subject: Re: [Proj] Standard projection for Mediterranean basin

		On Sunday 14 February 2010 11:46:30 pm Clifford J Mugnier wrote:
		> From 1925 to 1946, there was a "British Grid" used by the Allied Forces in
		> the Mediterranean.  The British Army (GSGS) established the "Mediterranean
		> Zone" for the secant Lambert Conical Orthomorphic Projection where the
		> central meridian was 29° East of Greenwich, and the latitude of origin was
		> 39° 30' N, the scale factor at origin was 0.99906, the False Easting was
		> 900 km, and the False Northing was 600 km.
		>
		> See my column in PE&RS for December of 2002 on Greece.
		>
		> Clifford J. Mugnier, C.P., C.M.S.
		        ...

		I had the inference that the request was for an equal-area projection---a mode
		that I consider preferable for thematic purposes.

		--
		The whole religious complexion of the modern world is due
		to the absence from Jerusalem of a lunatic asylum.
		-- Havelock Ellis (1859-1939) British psychologist
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