[Proj] Standard projection for Mediterranean basin
Jan Hartmann
j.l.h.hartmann at uva.nl
Mon Feb 15 13:05:19 PST 2010
What's the 1/6 rule, Daan, and how much does it deviate from the optimal
formula?
BTW Nice Java applet to study projection deformations here:
http://www.uff.br/mapprojections/Albers_en.html
Pity they didn't make it possible to alter projection parameters like
standard parallels.
Jan
On 15-2-2010 21:04, strebe wrote:
>
> 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/
>> <https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/exchweb/bin/redir.asp?URL=https://email.lsu.edu/%20%20exchweb/bin/redir.asp?URL=https://email.lsu.edu/%20exchweb/bin/redir.asp?URL=https://email.l>
>> ======================================================
>>
>> ------------------------------------------------------------------------
>> *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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