The maximum zoom level supported by the tiles of this overlay object.
- iOS 7.0+
- macOS 10.9+
- tvOS 9.2+
If you use different overlay objects to represent different tiles at different zoom levels, use this property to specify the maximum zoom level supported by this overlay’s tiles. At zoom level 0, tiles cover the entire world map; at zoom level 1, tiles cover 1/4 of the world; at zoom level 2, tiles cover 1/16 of the world, and so on. The map never tries to load tiles for a zoom level greater than the value specified by this property.
The default value of this property is 21. Setting the value of this property to a number greater than the default does not guarantee the use of those extra zoom levels.