<html><head></head><body name="Mail Message Editor"><div><br></div><div>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.</div><div><br></div><div>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.</div><div><br></div><div>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.</div><div><div><br></div></div><div>Regards,</div><div><div>— daan Strebe</div><div><br></div><div><br></div><div>On Feb 15, 2010, at 9:31:45 AM, "Jan Hartmann" <j.l.h.hartmann@uva.nl> wrote:<br><blockquote style="padding-left: 5px; margin-left: 5px; border-left-width: 2px; border-left-style: solid; border-left-color: blue; color: blue; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><div style="width: 749px; "><div id="felix-mail-header-block" style="color: black; background-color: white; border-bottom-width: 1px; border-bottom-style: solid; border-bottom-color: silver; padding-bottom: 1em; margin-bottom: 1em; width: 749px; "><table border="0" cellpadding="1" cellspacing="1" width="100%"><tbody><tr><td width="70px" style="font-family: 'Lucida Grande'; font-size: 8pt; color: gray; text-align: right; vertical-align: top; font-weight: bold; "><span>From:</span></td><td style="font-family: 'Lucida Grande'; font-size: 8pt; color: black; text-align: left; vertical-align: top; padding-left: 5px; "><span title=""Jan Hartmann" <j.l.h.hartmann@uva.nl>">"Jan Hartmann" <j.l.h.hartmann@uva.nl></span></td></tr><tr><td width="70px" style="font-family: 'Lucida Grande'; font-size: 8pt; color: gray; text-align: right; vertical-align: top; font-weight: bold; "><span>Subject:</span></td><td style="font-family: 'Lucida Grande'; font-size: 8pt; color: black; text-align: left; vertical-align: top; padding-left: 5px; "><span style="font-weight: bold; ">Re: [Proj] Standard projection for Mediterranean basin</span></td></tr><tr><td width="70px" style="font-family: 'Lucida Grande'; font-size: 8pt; color: gray; text-align: right; vertical-align: top; font-weight: bold; "><span>Date:</span></td><td style="font-family: 'Lucida Grande'; font-size: 8pt; color: black; text-align: left; vertical-align: top; padding-left: 5px; "><span>February 15, 2010 9:31:45 AM PST</span></td></tr><tr><td width="70px" style="font-family: 'Lucida Grande'; font-size: 8pt; color: gray; text-align: right; vertical-align: top; font-weight: bold; "><span>To:</span></td><td style="font-family: 'Lucida Grande'; font-size: 8pt; color: black; text-align: left; vertical-align: top; padding-left: 5px; "><span title=""PROJ.4 and general Projections Discussions" <proj@lists.maptools.org>">"PROJ.4 and general Projections Discussions" <proj@lists.maptools.org></span></td></tr></tbody></table></div><div id="felix-mail-content-block" style="color: black; background-color: white; width: 749px; "><div>Could you explain the relationship between Authalic Latitude and Equal Area projections? There is an article by John Snyder at<a class="moz-txt-link-freetext" href="http://www.jstor.org/stable/2562645?seq=1" title="http://www.jstor.org/stable/2562645?seq=1">http://www.jstor.org/stable/2562645?seq=1</a>, but it's a bit above my mathematical head.<br><br>Jan<br><br>On 15-2-2010 18:01, Clifford J Mugnier wrote:<blockquote cite="mid:B597ADFC46B67741B18EA6AA13613FF7EC29EF@email002.lsu.edu" type="cite"><div id="idOWAReplyText66217" dir="ltr"><div dir="ltr"><font color="#000000" face="Times New Roman" size="2">So?</font></div><div dir="ltr"> </div><div dir="ltr"><font size="2">Keep the parameters and just use Authalic Latitude.</font></div><div dir="ltr"> </div><div dir="ltr"><font size="2">Easy.</font></div><div dir="ltr"> </div></div><div id="idSignature82813" dir="ltr"><div><font color="#000000" face="Times New Roman" size="2"><span style="font-size: 10pt; ">Clifford J. Mugnier, C.P., C.M.S.<br>Past National Director (2006-2008),<br>Photogrammetric Applications Division<br>American Society for Photogrammetry and Remote Sensing<span class="Apple-converted-space"> </span><br>and<span class="Apple-converted-space"> </span><br>Chief of Geodesy,</span></font></div><div><font color="#000000" face="Times New Roman" size="2"><span style="font-size: 10pt; "><span style="font-size: 10pt; color: black; font-family: 'Times New Roman', serif; font-variant: small-caps; ">Center for GeoInformatics</span></span></font></div><div><font color="#000000" face="Times New Roman" size="2"><span style="font-size: 10pt; "><span style="font-size: 10pt; color: black; font-family: 'Times New Roman', serif; font-variant: small-caps; "></span>Department of Civil Engineering<span class="Apple-converted-space"> </span><br>Patrick F. Taylor Hall 3223A<br><strong>LOUISIANA STATE UNIVERSITY</strong><span class="Apple-converted-space"> </span><br>Baton Rouge, LA 70803<br>Voice and Facsimile: (225) 578-8536 [Academic]<span class="Apple-converted-space"> </span><br>Voice and Facsimile: (225) 578-8925 [Research]<span class="Apple-converted-space"> </span><br>Honorary Life Member of the<span class="Apple-converted-space"> </span><br>Louisiana Society of Professional Surveyors<span class="Apple-converted-space"> </span><br>Member Emeritus of the ASPRS<span class="Apple-converted-space"> </span><br>Member of the Americas Petroleum Survey Group<br>======================================================<br></span><a moz-do-not-send="true" href="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/ exchweb/bin/redir.asp?URL=https://email.lsu.edu/%20exchweb/bin/redir.asp?URL=https://email.l" target="_blank"><span style="font-size: 10pt; ">http://www.asprs.org/resources/GRIDS/</span></a><br><span style="font-size: 10pt; ">======================================================</span></font></div></div><div dir="ltr"><br><hr tabindex="-1"><font face="Tahoma" size="2"><b>From:</b><span class="Apple-converted-space"> </span><a class="moz-txt-link-abbreviated" href="mailto:proj-bounces@lists.maptools.org">proj-bounces@lists.maptools.org</a><span class="Apple-converted-space"> </span>on behalf of Gerald I. Evenden<br><b>Sent:</b><span class="Apple-converted-space"> </span>Mon 15-Feb-10 08:30<br><b>To:</b><span class="Apple-converted-space"> </span>PROJ.4 and general Projections Discussions<br><b>Subject:</b><span class="Apple-converted-space"> </span>Re: [Proj] Standard projection for Mediterranean basin<br></font><br></div><div><p><font size="2">On Sunday 14 February 2010 11:46:30 pm Clifford J Mugnier wrote:<br>> From 1925 to 1946, there was a "British Grid" used by the Allied Forces in<br>> the Mediterranean. The British Army (GSGS) established the "Mediterranean<br>> Zone" for the secant Lambert Conical Orthomorphic Projection where the<br>> central meridian was 29° East of Greenwich, and the latitude of origin was<br>> 39° 30' N, the scale factor at origin was 0.99906, the False Easting was<br>> 900 km, and the False Northing was 600 km.<br>><br>> See my column in PE&RS for December of 2002 on Greece.<br>><br>> Clifford J. Mugnier, C.P., C.M.S.<br> ...<br><br>I had the inference that the request was for an equal-area projection---a mode<br>that I consider preferable for thematic purposes.<br><br>--<br>The whole religious complexion of the modern world is due<br>to the absence from Jerusalem of a lunatic asylum.<br>-- Havelock Ellis (1859-1939) British psychologist<br>_______________________________________________<br>Proj mailing list<br><a class="moz-txt-link-abbreviated" href="mailto:Proj@lists.maptools.org">Proj@lists.maptools.org</a><br><a moz-do-not-send="true" href="http://lists.maptools.org/mailman/listinfo/proj">http://lists.maptools.org/mailman/listinfo/proj</a></font></p></div><pre wrap=""><fieldset class="mimeAttachmentHeader"></fieldset>
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