The iPhone comes with several applications installed on it, including the Maps application. With the Maps application, you can view maps of a certain area or get driving directions. If you need to view Maps while driving, you may want to keep your iPhone on so it will be easier for you to view a map or directions. By default, your iPhone locks after not being used. You must turn off auto-lock to keep your iPhone on while using Maps.
Unlock your iPhone by pressing the Home button and sliding the bar on the touch screen where it says "Slide to unlock."
Tap the "Settings" button. Some settings you can view or change here include notifications, wallpaper and general settings.
Tap "General" from the list of settings options. You can view Bluetooth, network and auto-lock settings here.
Tap "Auto-Lock." The auto-lock options will open. You can set your iPhone to lock after not being used for one to five minutes, or you can turn off auto-lock.
Select "Never" from the list of auto-lock options and then open the Maps application. The iPhone will stay on while using Maps. To save battery usage, change back your auto-lock settings after you are finished with Maps.
Make sure your iPhone is fully charged if you plan to use the Maps application on a long trip. When you turn off auto-lock, the iPhone battery won't stay charged as long.