Being new at this as well i can tell you that when i use the app i will get "close" to the cache and all of a sudden it will change direction and tell me i have 45 feet to go. So seeing as i work with a bunch if electrical engineers i reached out and ask "how is this happening"? the most common response i got back was:
(1)A cell phone is dependant on a cell tower therefore you must be in range of a tower for your cell phone GPS to work.
(2) the further you are away from a tower you cell phone will boost the power in order to connect to the tower and the closer you are it will reduce power.
(3) keep in mind that anything obstructing the siginal (IE: trees, buildings and even yourself) will throw off your GPS.
(4) the last bit of advice they gave me was "go buy a cheap GPS unit" So I did and have had no issues since.
Power Guy