I think the above posts probably assumed that you were expecting to need height, width and weight information entered in your GPS, rather than campground information. There is a Garmin, a Rand McNally, and probably a couple more GPSs aimed at RVs, and yes they include some campground information (I don't have one, so don't know how much), but I use Allstay's Camp & RV app for my phone, for campground information. It includes just about all the commercial campgrounds, city, state and National parks, Forest Service, Corps of Engineers and other campgrounds, along with a list of many Wlmarts, rest areas and other such where you might spend a night.
On each campground, it lists not only how many of what type site (back in, pull thru, full hookup, electric only), amenities (pool, etc.) and much more, including phone numbers and websites (plus it'll dial the phone number for you, if you wish). It'll even display a map and guide you to the campground (if you have internet service, of course).
Someone else will have to give you more info on RV GPSs.