As with every morning... stop outside, calibrate to 48m.
If I was transitioning I'd have to do it while inside the Tri app.
10 keypresses (yes, wear those buttons, Garmin Tech Support will be happy!), 2 minutes lost... for a watch that cost 800€ and that has shortcuts among its features. I find this totally absurd.
Before someone starts lecturing on how handy the GPS autocalibration feature is, keep in mind what it is to be in a dense urban area. It simply is not an option.
Please Garmin add a shortcut feature that makes sense: pre-set altitude inputting. WE HAVE THE TECHNOLOGY.