KML图层未显示在Google地图上

Question

自从我使用KML已经有一段时间了，所以我可能会遗漏一些明显的东西，我知道它与我的坐标有关

<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://www.opengis.net/kml/2.2">
  <Placemark>
    <name>A Rectangle</name>
    <Polygon>
      <extrude>1</extrude>
      <altitudeMode>relativeToGround</altitudeMode>
      <outerBoundaryIs>
        <LinearRing>
          <coordinates>
            51.078523,-114.134937,50
            51.078523,-114.133737,50
            51.077323,-114.133737,50
            51.077323,-114.133937,50
          </coordinates>
        </LinearRing>
      </outerBoundaryIs>
    </Polygon>
  </Placemark>
</kml>