Google Maps relies on a data connection to operate. Fortunately, there is a way to use Google Maps without one. Download the map of the area before you arrive. First, ensure you're connected to the Internet and open Google Maps. In the search field, enter your destination (e.g. New York City), then tap on the settings/account icon on the top right of the screen. On the subsequent menu, tap "Offline Maps -> Select Your Own Map," which opens a map of the area you previously entered. You can customize the area by dragging and pinching the map. Once you've selected the area, tap the "Download" button. The map will be saved locally to your device to use for navigation, even without a data connection.