The offline map is scaled to online maps, brings you a peace of mind when you know where you are when internet is not available and you are in/outside the Grand Canyon National Park
By using the phone offline, your phones battery can last a lot longer.
In case get lost, you can plot your locations latitude, longitude and notify people who are trying to locate you (you must first grand app access to your location by clicking the green star on the main map page)
You can do a lot more with the app such as recording then sharing your trips as named trails with friends, displaying your friends locations, contact sharing, note keeping, timer, fitness etc.