I am planning a major trip around the USA this summer with my travel trailer. I am interested in finding a high quality map app for use on the road. It needs have the maps available off-line as my iPad 1 is the wifi only version. I would like to have a large scale US map that shows the interstate highways for long range planning and the ability to access state, county, and cuty maps as the need arises. I have spent some time in the app store, but nothing appears to meet my needs. Can anyone here help?