+// Determine scenery altitude. Normally this just happens when we
+// render the scene, but we'd also like to be able to do this
+// explicitely. lat & lon are in radians. abs_view_pos in meters.
+// Returns result in meters.
+double fgTileMgrCurElev( double lon, double lat, fgPoint3d *abs_view_pos );
+
+