My wife and I are full time RV'ers. Currently we are in Island Park, ID about 20 miles from Yellowstone. In our park my LG3 and Iphone6+ have 3G service, my LG tablet sitting next to the phones have no signal. The Verizon service map shows a field of red in Idaho with a small white circle where my location is marked.I can drive 1/4 mile and have 4GLTE service. This is a regular occurrence on the road. What can fi x this?
What can fix this? More towers can fix this. Unfortunately, cellular service is NOT designed to give you service in ALL locations and service is not guaranteed in any given location. Erecting additional towers to give added service is not always an option as approval from local governing bodies must be obtained in order to erect those towers. Since the area you are interested in is in/around a national park which in large part is attractive mainly due to its visual pleasures, additional cell towers in the area which would detract from those visual pleasures are even LESS likely to happen.
It seems you have already found the most likely fix you are going to get. Drive the 1/4 mile to the area you receive service for when you need to use it.
Cellular service is dependent upon towers to provide the service. Placement of those towers are dependent upon local governing bodies giving the approval needed to build those towers. Placement is not dependent upon where cellular customers would like to have service OR where providers would necessarily like to erect towers. More often than not, towers are erected where providers are ALLOWED to erect towers, not simply where the best location for a tower would be.