Pecosmud

One example of those compact drill rigs for underground exploration is shown in the link below. There are a lot more videos on this topic if you are interested and have the time to watch. One advantage is that drilling, as shown in the video, can be done in all directions. This is an economic way to locate satellite deposits. This can be assisted with in-situ survey by inserting a probe in an existing drill hole to look around in "360 degrees".

Hope this helps.

https://www.youtube.com/watch?v=2UlXX2fnf_A

goldhunter