[Esip-documentation] geospatial_bounds: how to show 3-D bbox?

[Aleksandar Jelenak]

Hello John,

On Jan 24, 2017, at 1:47 PM, John Maurer via Esip-documentation <esip-documentation at lists.esipfed.org<mailto:esip-documentation at lists.esipfed.org>> wrote:

Actually, I believe there is more to this topic. The spec says the order should follow the CRS given*. For EPSG:4326<http://spatialreference.org/ref/epsg/wgs-84/>, the order is lon lat. For CRS:84, the order is lat lon. Yes, confusing, but stuck that way for legacy reasons. So, I believe it depends on geospatial_bounds_crs. In my case (and in many cases, I'm guessing, including the ACDD default), I'm setting geospatial_bounds_crs to ESPG:4326, so I believe I (and your wiki example) should use lon lat order in geospatial_bounds. This also trips up people a lot in WMS 1.3.0 requests, where lon lat order switches between EPSG:4326 and CRS:84 (one example<https://viswaug.wordpress.com/2009/03/15/reversed-co-ordinate-axis-order-for-epsg4326-vs-crs84-when-requesting-wms-130-images/>). Thoughts?

Actually, the axis order in ESPG:4326 is (lat, lon) and so the wiki example is correct.

The confusion in lat-lon axis ordering is well documented as you point out and there are many resources on the Web that provide “alternate facts”.

This web page states the lat-lob ordering in the most visible way: https://epsg.io/4326, and look for “Coordinate System”. For the spatial reference.org<http://reference.org> link you provided, the GML XML reveals the same:

  <gml:usesEllipsoidalCS>
    <gml:EllipsoidalCS gml:id="ogrcrs842">
      <gml:csName>ellipsoidal</gml:csName>
      <gml:csID>
        <gml:name gml:codeSpace="urn:ogc:def:cs:EPSG::">6402</gml:name>
      </gml:csID>
      <gml:usesAxis>
        <gml:CoordinateSystemAxis gml:id="ogrcrs843" gml:uom="urn:ogc:def:uom:EPSG::9102">
          <gml:name>Geodetic latitude</gml:name>
          <gml:axisID>
            <gml:name gml:codeSpace="urn:ogc:def:axis:EPSG::">9901</gml:name>
          </gml:axisID>
          <gml:axisAbbrev>Lat</gml:axisAbbrev>
          <gml:axisDirection>north</gml:axisDirection>
        </gml:CoordinateSystemAxis>
      </gml:usesAxis>
      <gml:usesAxis>
        <gml:CoordinateSystemAxis gml:id="ogrcrs844" gml:uom="urn:ogc:def:uom:EPSG::9102">
          <gml:name>Geodetic longitude</gml:name>
          <gml:axisID>
            <gml:name gml:codeSpace="urn:ogc:def:axis:EPSG::">9902</gml:name>
          </gml:axisID>
          <gml:axisAbbrev>Lon</gml:axisAbbrev>
          <gml:axisDirection>east</gml:axisDirection>
        </gml:CoordinateSystemAxis>
      </gml:usesAxis>
    </gml:EllipsoidalCS>

Regards,

Aleksandar
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