If you normally have no bars in that area, your phone may be constantly searching for a signal. You might want to consider switching to airplane mode to stop that... Just be aware that you won't have call/text while in this mode. This will also keep mobile data off although WiFi can be turned on and used in airplane mode.
Another thing you can try is get the 'betterbatterystats' app from these forums and check for unwanted 'wakelocks' after it's been installed for a few hours or more.
Sidenote: Having location (gps) ticked on all the time shouldn't drain your battery, but turning off the internet (mobile data/Wifi) when not using it is a good idea as you've been doing.
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