You can get a Topographical map/GPS app called Topo Map NZ for your android phone from the app store.
It's about $10 and will give you a maps of the whole country down to a 1:50,000 scale.
Two tricks to using it:
One - Preload the map of the area you intend to go hunting in while you still have internet access (i.e. at home with wifi) otherwise you won't be able to see the map just your co-ords.
When you have viewed the map of an area once your phone should store it, so you should only have to do it once for each new area.
Two - While in the bush turn on flight mode, you will lose the ability to call but your phone's GPS will still work and your phone's battery will last heaps longer.
Bookmarks