]> RDFMap Asserts tthat the edge or boundary of a geo:SpatialThing (such as a park or body of water) is a specified geom2d:Shape. Asserts that the center line of a linear feature, such as a road or river, is a specified geom2d:Shape. Spatial reference system Background image thumbnail specifies a small image used to denote the map in web documents. The coverage of a map specifies the range of points on the earth that the map covers, using the map's srs. The extent is the box representing the map's viewport onto the canvas. This property is an alternative to srs, and is applicable to any located entity (such as a Point or an RSS channel or item, or even another Map). If a resource has the canvas property, the values of the x and y properties of its contents are interpreted in the canvas coordinates of the map that is the value of canvas. The useMap property asserts that its value is a map that can be used to depict its subject. For example, an RSS channel might have a useMap property whose value is a map recommended for depicting the contents of the channel.