I was on Minecraftforum and saw a mod that can help you find rare materials with a vertical and horizontal map. I saw the vertical map and it gave me this idea. Create a ground penetrating radar that "for an example" can scan a 1x10xY picture of some kind. So if you are wanting to go cave diving it can lead you where you want to go faster. Now the thing is I don't want it to make it easier to find materials just to find cave so maybe a black and white interpretation of the small chunk you are scanning to differentiate the air and solid material. There can also be blue and red added to those colors for water and lava.
If you like this idea feel free tell me a way i can improve it.
If you're against this idea please comment on why you think this is a bad idea.
If you're a modder and want to create this please go right ahead.