+/**
+ * gis_tile_update:
+ * @root: the root tile to split
+ * @res: a maximum resolution in meters per pixel to split tiles to
+ * @width: width in pixels of the image associated with the tile
+ * @height: height in pixels of the image associated with the tile
+ * @lat: latitude of the eye point
+ * @lon: longitude of the eye point
+ * @elev: elevation of the eye point
+ * @load_func: function used to load the image when a new tile is created
+ * @user_data: user data to past to the load function
+ *
+ * Recursively split a tile into children of appropriate detail. The resolution
+ * of the tile in pixels per meter is compared to the resolution which the tile
+ * is being drawn at on the screen. If the screen resolution is insufficient
+ * the tile is recursively subdivided until a sufficient resolution is
+ * achieved.
+ */