What decides your dash?

Ground dashing can be a great way to keep up speed, however there are multiple factors to determine if it will be an air dash or a ground dash, with air dashing wasting lots of time.
-You have vertical momentum of any kind. You cannot ground dash while falling or rising in the air, and this is ANY vertical momentum, so dashing while going down stairs is a bad idea. However, when going up a ledge, you will not actually have any momentum vertically, so you can dash up stairs. You can also time your dash to where you have 0 vertical momentum after losing all upwards momentum from a jump of any kind before you start falling.
-You are underwater. You will do air dashes underwater unless you are standing still on the floor underwater, so stay out of water. Nothing but a loss of speed.