When you look at the LED's on the rear of the craft and it flashes green red red, you only have 4 satellites, flashing green then red you have five satellites the flashing rapidly green you have satellite lock with 6 or more satellites. That's the only other way without tellimetry data telling you.
In Naza the lights are as follow. 1st flash green means gps mode. 1st flash yellow means Atti or non gps. Then....either of those followed by 3 red means less than 5 satellites, followed by 2 reds mean 5 satellites, followed by 1 means 6 satellites. All flashing green more than 6. So you could fly with green and 1 red flash, but I wouldn't. I like all green. Hope that helps. Jack