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<pre><font face="Times New Roman">This OGC document:</font></pre>
<pre><span class="Apple-tab-span" style="font-family: 'Times New Roman';"> </span><font face="Times New Roman"><a href="http://docs.opengeospatial.org/is/12-063r5/12-063r5.html#41">http://docs.opengeospatial.org/is/12-063r5/12-063r5.html#41</a></font></pre>
<pre><pre><font face="Times New Roman">says:</font></pre></pre>
<pre><div style="font-family: 'Times New Roman'; white-space: normal;"></div><blockquote type="cite"><div style="font-family: 'Times New Roman'; white-space: normal;">7.5.5Axis order</div><br style="font-family: 'Times New Roman'; white-space: normal;"><span style="font-family: 'Times New Roman'; white-space: normal;">Axis is repeated in a sequence. The number of axes in the sequence is the same as the dimensions of the</span><span style="font-family: 'Times New Roman'; white-space: normal;"> </span><span style="font-family: 'Times New Roman'; white-space: normal;">coordinate system.</span><br style="font-family: 'Times New Roman'; white-space: normal;"><br style="font-family: 'Times New Roman'; white-space: normal;"><div><span style="font-family: 'Times New Roman'; white-space: normal;"><b><axis order> identifies the order in which the coordinates of a point in a dataset are given and therefore is significant.</b> In this International Standard it is defined in the BNF as an optional attribute to allow backward compatibility with OGC 01-009, however it is recommended that it should be explicitly included in a CRS WKT string.</span><font face="Times New Roman"></font></div></blockquote><blockquote type="cite"><br></blockquote><blockquote type="cite"><div><font face="Times New Roman"><span style="white-space: normal;">Requirement:The following constraints shall apply:</span></font></div></blockquote><font color="#0f61c8" face="Times New Roman"><span style="white-space: normal;"></span></font><blockquote type="cite"><div><font color="#0f61c8" face="Times New Roman">• For coordinate systems with more than one axis, either every axis description </font> </div></blockquote><blockquote type="cite"><div></div></blockquote><blockquote type="cite"><div><font color="#0f61c8"> </font><font color="#0f61c8" face="Times New Roman">shall include an <order> or none of the axes descriptions shall include an <order>. </font></div></blockquote><blockquote type="cite"><div><font color="#0f61c8"> </font><font color="#0f61c8" face="Times New Roman">If <order> is included a sequence value shall not be repeated.<br></font></div><div><font color="#0f61c8" face="Times New Roman">• When <axis order> is present in the WKT string the <axis> descriptions shall be ordered </font></div></blockquote><blockquote type="cite"><div><font color="#0f61c8" face="Times New Roman"> according to the axis order sequence.<br></font></div><div><font color="#0f61c8" face="Times New Roman"><b>• If <axis order> is omitted from the WKT string the sequence of <axis> descriptions </b></font></div></blockquote><blockquote type="cite"><div><font color="#0f61c8" face="Times New Roman"><b> shall imply the order of the axes and of coordinates referenced to the CRS.</b></font></div></blockquote><div><font face="Times New Roman"><br></font></div><div><font face="Times New Roman">and gives these three examples of geographic coordinate systems, all of which place latitude <i>before </i>longitude:</font></div></pre>
<div> GEODCRS[“WGS 84”,</div>
<div> DATUM[“World Geodetic System 1984”,</div>
<div> ELLIPSOID[“WGS 84”,6378137,298.257223563,</div>
<div> LENGTHUNIT[“metre”,1.0]]],</div>
<div> CS[ellipsoidal,3],</div>
<div> AXIS["(lat)“,north,ANGLEUNIT[”degree",0.0174532925199433]],</div>
<div> AXIS["(lon)“,east,ANGLEUNIT[”degree",0.0174532925199433]],</div>
<div> AXIS[“ellipsoidal height (h)”,up,LENGTHUNIT[“metre”,1.0]]]</div>
<br class="Apple-interchange-newline">
GEODCRS[“NAD83”,<br>
<div>
<div> DATUM[“North American Datum 1983”,</div>
<div> ELLIPSOID[“GRS 1980”,6378137,298.257222101,LENGTHUNIT[“metre”,1.0]]],</div>
<div> CS[ellipsoidal,2],</div>
<div> AXIS[“latitude”,north],</div>
<div> AXIS[“longitude”,east],</div>
<div> ANGLEUNIT[“degree”,0.017453292519943],</div>
<div> ID[“EPSG”,4269],</div>
<div> REMARK[“1986 realisation”]]</div>
<br>
<div> GEODCRS[“NTF (Paris)”,</div>
<div> DATUM[“Nouvelle Triangulation Francaise”,</div>
<div> ELLIPSOID[“Clarke 1880 (IGN)”,6378249.2,293.4660213]],</div>
<div> PRIMEM[“Paris”,2.5969213],</div>
<div> CS[ellipsoidal,2],</div>
<div> AXIS[“latitude”,north,ORDER[1]],</div>
<div> AXIS[“longitude”,east,ORDER[2]],</div>
<div> ANGLEUNIT[“grad”,0.015707963267949],</div>
<div> REMARK[“Nouvelle Triangulation Française”]]</div>
<br>
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<div>PostGIS should use this information to understand the data in your polygon representation. Is your polygon defined correctly given some particular GCS, or was it generated incorrectly and its too much trouble to regenerate it? In the latter case perhaps
you could define your own GCS that simply reverses the order. In either case, apply ST_Transform?</div>
<div><br>
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<div><span class="Apple-tab-span" style="white-space:pre"></span><a href="http://postgis.net/docs/ST_Transform.html">http://postgis.net/docs/ST_Transform.html</a></div>
<div><br>
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<div>— Andy</div>
<div><br>
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<div>
<div>On Nov 17, 2015, at 10:09 AM, Willy-Bas Loos <<a href="mailto:willybas@gmail.com">willybas@gmail.com</a>> wrote:</div>
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<blockquote type="cite">
<div dir="ltr">
<div>Hi,<br>
<br>
</div>
<div>I have a couple of questions about the order of lattitude and longitude in WKT representations of geometries:<br>
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<ol>
<li>Is there an objective reference that states in what order WGS84 (geographic) coordinates should be represented in a WKT? Is it lon, lat (because of x,y) or lat,lon (because it's geodetic) ?<br>
</li><li>Does postgis use the correct representation?</li><li>Is there a way to switch lat and lon for a polygon when representing as WKT? All i think of is looping through all points, switching x and y and then returning astext(g)<br>
</li></ol>
Cheers,<br clear="all">
<div><br>
-- <br>
<div class="gmail_signature">
<div dir="ltr">Willy-Bas Loos<br>
</div>
</div>
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