You will find that your phone's GPS is not accurate enough to get you to the treasure. It will get you close but some of those caches are so well hidden that if you are not within 5' you will never find it. 20-30 feet isn't gonna get it. Additionally, try your GPS while you are under some trees (that's where the caches are) and you will find it causing you to wander all over the place as the antenna is just not sensitive enough.
What I post is my 2 cents and nothing more. Please don't read anything into my post that's not there. If you disagree, that's OK.
Can't we all just get along?