Many of you are probably already aware of this, but no internet connection is required to get GPS position and altitude on an IOS device, as long as it has a cellular antenna. (All iPhones obviously do, and it's an option on iPads.) An app that provides this info is the perfect companion to these topo maps.
The app I use to provide raw data is AltimeterGPS:
Incidentally, if you're traveling to a new city, an app called CityMaps2Go takes advantage of this GPS capability. The idea is that you download a map of the city before you leave home (or the hotel), because once you're outside you won't have a reliable internet connection. Then, as you walk around the town, you get a moving blue dot on the map indicating your position. I've used this app to navigate twisted streets and back alleys in many European cities, and it's incredibly accurate; it's not uncommon for locals to ask me for directions.