Yeah i'm high up, no worries. I am higher than 10 walls though, since i need plenty of airspace to do my favourite thing: jumping the dunes at high speed in my Explorer!
I realized that i had just searched for the nodes by looking at the ground, not trying to put down a miner anyway. I just tried it, and it works fine to put down miners even though the HUD doesn't say there is anything there. :)