Don't know if this will be of much help, but here goes.
Memory map has a northern hemisphere base map that you can load onto the iphone but it doesn't appear to be very detailed. You can load other maps into memory map but there is a licence to buy before you can do this.
I use memory map occasionally when out walking in the hills. Works really well and very accurate satellite location. It's heavy on the power though. I also have co-pilot which I use sometimes in the car/on the bike. However, even when plugged in to the cig charger the app drains power faster than the phone can charge itself, so 6 or 7 hours at best if using constantly.
I'm sure someone else will have a better suggestion...