Editing Geography Markup Language (section)

==Examples==

[[Polygon]]s, [[Point (geometry)|Point]]s, and ''LineString'' objects are encoded in GML 1.0 and 2.0 as follows:

<syntaxhighlight lang="xml">
     <gml:Polygon>
         <gml:outerBoundaryIs>
                 <gml:LinearRing>
                         <gml:coordinates>0,0 100,0 100,100 0,100 0,0</gml:coordinates>
                 </gml:LinearRing>
        </gml:outerBoundaryIs>
     </gml:Polygon>
     <gml:Point>
        <gml:coordinates>100,200</gml:coordinates>
     </gml:Point>
     <gml:LineString>
        <gml:coordinates>100,200 150,300</gml:coordinates>
     </gml:LineString>
</syntaxhighlight>

''LineString'' objects, along with ''LinearRing'' objects, assume linear interpolation between the specified points. Also the coordinates of a Polygon have to be closed.

===Features using geometries===

The following GML example illustrates the distinction between ''features'' and ''geometry objects''.  The ''Building'' feature has several ''geometry objects'', sharing one of them (the ''Point'' with identifier ''p21'') with the ''SurveyMonument'' feature:

<syntaxhighlight lang="xml">
 <abc:Building gml:id="SearsTower">
     <abc:height>52</abc:height>
     <abc:position xlink:type="Simple" xlink:href="#p21"/>
 </abc:Building>
 <abc:SurveyMonument gml:id="g234">
     <abc:position>
         <gml:Point gml:id="p21">
             <gml:posList>100,200</gml:posList>
         </gml:Point>
     </abc:position>
 </abc:SurveyMonument>
</syntaxhighlight>

The reference is to the shared ''Point'' and not to the ''SurveyMonument'', since any ''feature'' object can have more than one ''geometry object'' property.

===Point Profile===

The GML ''Point Profile'' contains a single GML geometry, namely a {{code|<gml:Point>}} object type. Any XML Schema can use the ''Point Profile'' by importing it and referencing the subject {{code|<gml:Point>}} instance:

<syntaxhighlight lang="xml">
 <PhotoCollection xmlns="http://www.myphotos.org" xmlns:gml="http://www.opengis.net/gml"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
      xsi:schemaLocation="http://www.myphotos.org
      MyGoodPhotos.xsd">
     <items>
         <Item>
             <name>Lynn Valley</name>
             <description>A shot of the falls from the suspension bridge</description>
             <where>North Vancouver</where>
             <position>
                 <gml:Point srsDimension="2" srsName="http://www.opengis.net/def/crs/EPSG/0/4326">
                     <gml:pos>49.40 -123.26</gml:pos>
                 </gml:Point>
             </position>
         </Item>
     </items>
 </PhotoCollection>
</syntaxhighlight>

When using the ''Point Profile'', the only geometry object is the '<gml:Point>' object. The rest of the geography is defined by the photo-collection schema.