Circle by Center Point

Full circles are also used in order to define the geometry of certain airspace in the AI domain. They can be directly encoded using the gml:CircleByCenterPoint. It is quite deep in the structure, as presented in the example below.

...
        <aixm:Surface gml:id="S001" srsName="urn:ogc:def:crs:EPSG::4326">
            <gml:patches>
                <gml:PolygonPatch>
                    <gml:exterior>
                        <gml:Ring>
                            <gml:curveMember>
                                <gml:Curve gml:id="CUR001">
                                    <gml:segments>
                                        <gml:CircleByCenterPoint numArc="1">
                                            <gml:pos>51.01555556 2.57138889</gml:pos>
                                            <gml:radius uom="[nmi_i]">12</gml:radius>
                                        </gml:CircleByCenterPoint>
                                    </gml:segments>
                                </gml:Curve>
                            </gml:curveMember>
                </gml:Ring>
                    </gml:exterior>
                </gml:PolygonPatch>
            </gml:patches>
        </aixm:Surface>
...

Note

CircleByCenterPoint should be used only to define a simple circular airspace boundary and it should appear as unique member of a gml:Curve. Otherwise, the orientation of the circle boundary is not well defined.