Hi, I'm pretty much new to robotic, even though I've worked with kit like fischertechnik and Lego NXT.
I know the base of it, and i'm good with electronics.
but here it is i want to build plane that coud fly by itself using rangefinder (Ir or ultrasonic) to keep a distance from the ground, but i've read that IR sensor aren't good outside and that ultrasonic doesn't work good on absorbant material (Grass).
Since it's a plane I also have to consider weight in my choice.
Wich sensor would be the best for this task ?