Maps Available offline

I have the Garmin Tactix paired with the basecamp app on Iphone. What I want to do is pull up a map area that is stored in the basecamp app, use it to adjust my route and send it to the Tactix for navigation assist. Right now I do not have any purchased maps and before I do so I want to be sure this will work properly, as it looks right now the app requires a data connection to load maps and that isn't of any use in the in the backcountry. Or is there another Garmin handheld device to pair with for this purpose, trying to limit my gear... Thanks!