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<p>Jos<span style="FONT-FAMILY: 'Times New Roman', 'serif'; FONT-SIZE: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA"><font face="Times New Roman">é,</font></span></p>
<p><span style="FONT-FAMILY: 'Times New Roman', 'serif'; FONT-SIZE: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA"><font face="Times New Roman"></font></span> </p>
<p><span style="FONT-FAMILY: 'Times New Roman', 'serif'; FONT-SIZE: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA"><font face="Times New Roman">Plane coordinate systems comprised
of quadrants with plus & minus signs associated with coordinate components were common in Europe and many European colonies in the 19th century and some hold-overs remained during the first half of the 20th century. With regard to the "Great War," (WWI),
the French Kilometric Quadrillage used specifically in the Nord de Guerre Zone of Northern France and Belgium was the primary inspiration for the American series of the State Plane Coordinate Systems. After WWII, projection tables were published for all of
the American states and territories specifically for the land aeras. Little thought was given to developing geodetic plane coordinate systems for offshore areas of American territorial waters.</font></span></p>
<p><span style="FONT-FAMILY: 'Times New Roman', 'serif'; FONT-SIZE: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA"><font face="Times New Roman"></font></span> </p>
<p><span style="FONT-FAMILY: 'Times New Roman', 'serif'; FONT-SIZE: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA"><font face="Times New Roman">Metal welding technologies advanced
such that stiff-leg platforms were fabricated and moved offshore into the Gulf of Mexico to enable oil exploration and production activities. Over time, the platforms started being emplaced further and further offshore. Eventually, the offshore lease blocks
began being used that were far south of the False Origin of the Louisiana South (1702) Zone, and from time-to-time Licensed Surveyors would "forget" the minus sign on the Y-coordinate and the platform would be placed exactly on the X-coordinate but 20 miles
or so too far north of the intended location. The economic consequences were disasterous for all concerned, as one would expect.</font></span></p>
<p><span style="FONT-FAMILY: 'Times New Roman', 'serif'; FONT-SIZE: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA"><font face="Times New Roman"></font></span> </p>
<p><span style="FONT-FAMILY: 'Times New Roman', 'serif'; FONT-SIZE: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA"><font face="Times New Roman">The use of GPS for precise positioning
offshore seems to have alleviated that problem.</font></span></p>
<p><span style="FONT-FAMILY: 'Times New Roman', 'serif'; FONT-SIZE: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA"><font face="Times New Roman"></font></span> </p>
<p><span style="FONT-FAMILY: 'Times New Roman', 'serif'; FONT-SIZE: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA"><font face="Times New Roman">Minus signs on coordinates and
humans don't seem to mix very well.</font></span></p>
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<p><font face="Copperplate Gothic Bold">Clifford J. Mugnier, c.p., c.m.s.</font></p>
<p><font face="Copperplate Gothic Bold">Chief of Geodesy</font></p>
<p><font face="Copperplate Gothic Bold">LSU Center for GeoInformatics (ERAD 266)</font></p>
<p><font face="Copperplate Gothic Bold">Dept. of Civil Engineering (P.F. Taylor 3531)</font></p>
<p><font face="Copperplate Gothic Bold">LOUISIANA STATE UNIVERSITY</font></p>
<p><font face="Copperplate Gothic Bold">Baton Rouge, LA 70803</font></p>
<p><font face="Copperplate Gothic Bold">Academic: (225) 578-8536</font></p>
<p><font face="Copperplate Gothic Bold">Research: (225) 578-4578</font></p>
<p><font face="Copperplate Gothic Bold">Cell: (225) 328-8975</font></p>
<p><font face="Copperplate Gothic Bold">honorary lifetime member, lsps</font></p>
<p><font face="Copperplate Gothic Bold">fellow emeritus, asprs</font></p>
<p><font face="Copperplate Gothic Bold">member, apsg</font></p>
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<div dir="ltr" id="divRplyFwdMsg"><font style="FONT-SIZE: 11pt" color="#000000" face="Calibri, sans-serif"><b>From:</b> proj-bounces@lists.maptools.org <proj-bounces@lists.maptools.org> on behalf of Jose Gonçalves <jagoncal@gmail.com><br>
<b>Sent:</b> Monday, December 30, 2013 6:39 PM<br>
<b>To:</b> PROJ.4 and general Projections Discussions<br>
<b>Subject:</b> [Proj] Map projection of Portugal</font>
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<div dir="ltr"><span style="FONT-FAMILY: tahoma,sans-serif"><font size="+0">Dear members of the list<br>
<br>
I would like to put some questions related to map projections being used in Europe. Most of the European countries are now using map coordinate systems based on the ETRS89 datum. The Portuguese Geographical Institute has adopted in 2006, for the continental
Portugal, a projection, called “PT-TM06” (EPSG code 3763), similar to the ones used before with older geodetic datums (Datum Lisboa and Datum 73). It has, in my opinion, some annoying characteristics that make users loose time, and even make errors with costly
consequences. <br>
<br>
The projection is a transverse Mercator, with a central point in the centre of the country, no scale change, i.e. k_0=1, and no false easting/northing, so coordinates can be positive or negative. Some old coordinate systems in other countries also had the origin
inside the country or region, but I think that now, most of them do not have this situation. So, my first question is if anyone knows of map coordinate systems in use, for topographic surveying and cadastre, which have negative coordinates.<br>
<br>
The second bad aspect of our new coordinate system is that, being the projection similar to the older ones, coordinates are also very similar. Differences are in general smaller than 6 meters, so when one looks at a coordinate pair it is not obvious if it is
EPSG:3763 or older systems (datum 73, EPSG:27493 or datum Lisboa, EPSG:20791). For many years people will have to deal with data in the older systems, so making mistakes becomes very easy. The reasonable approach would have been to add a big shift so that
coordinates are not mistaken, as I think most countries do. This leads to my second question: does anyone know of similar situations of very close coordinate systems?
<br>
I know that in Belgium a projection was established for ETRS89 (Belge 2005, EPSG:3447) which had coordinates similar to an older system (EPSG:31300). Meanwhile a new system was defined with new false easting/northing (Belge 2008, EPSG:3812). Was the change
motivated by users?<br>
<br>
Regards and a happy new year<br>
<br>
Jose’ Gonçalves</font><br>
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