The best method to detect the distance between two elements

I would like to build an application that allows searching for hidden element A using element B. Element B should signal a decreasing distance to element A. There may be obstacles between these elements, for example element A may be up to 2 meters underground. The maximum distance between elements is 15 meters. What is the best method to detect the distance between two elements? What electronic components can be used?

"What is the best method to detect the distance between two elements? What electronic components can be used?"

kusmira:
I would like to build an application that allows searching for hidden element A using element B. Element B should signal a decreasing distance to element A. There may be obstacles between these elements, for example element A may be up to 2 meters underground. The maximum distance between elements is 15 meters. What is the best method to detect the distance between two elements? What electronic components can be used?

Short and sweet, it probably isn't going to happen the way you want or at the hobby level. You can use the forum search tool to find similar project discussions from the past and the outcomes.

kusmira:
I would like to build an application that allows searching for hidden element A using element B. Element B should signal a decreasing distance to element A. There may be obstacles between these elements, for example element A may be up to 2 meters underground. The maximum distance between elements is 15 meters. What is the best method to detect the distance between two elements? What electronic components can be used?

Not enough information I'm afraid - what are these elements? How large can they be? What's the power budget? Are there magnetic materials in the environment? Underground in what material - soil, bedrock, reinforced concrete? What kind of obstacle?

Details will matter, and its a very hard problem. My suspicion is that if the elements can be quite large then
magnetic loop antenna might be a possible method.

I would like to build an application that allows searching for hidden element A using element B. Element B should signal a decreasing distance to element A. There may be obstacles between these elements, for example element A may be up to 2 meters underground. The maximum distance between elements is 15 meters. What is the best method to detect the distance between two elements? What electronic components can be used?

It is rather curious that “Element-A” and “Element-B” are completely ambiguous and no information is given
as to exactly WHAT they are (physically).
Why is that ?
Why are you being so vague about WHAT these “elements” are ?

Think about it (from our viewpoint). Why have you not explained the reason (or objective) of this application ?

Are you aware that drug smugglers and terrorists routinely post on the forum for assistance building circuits for their nefarious purposes ?
Example-A: Poster requesting detail to construct circuit to “trigger” something 3 km away. (I’ll leave
you to guess what it was he wanted to “trigger”
Example-B: Poster requesting design help to construct an EMP device to “take out” a 3-square-block
area.

Now you’re asking us how to locate a “package” 2 meters underground.
Which Cartel do you work for ?
How long is the tunnel ?

raschemmel:
It is rather curious that "Element-A" and "Element-B" are completely ambiguous and no information is given
as to exactly WHAT they are (physically).
Why is that ?
Why are you being so vague about WHAT these "elements" are ?

Think about it (from our viewpoint). Why have you not explained the reason (or objective) of this application ?

Are you aware that drug smugglers and terrorists routinely post on the forum for assistance building circuits for their nefarious purposes ?
Example-A: Poster requesting detail to construct circuit to "trigger" something 3 km away. (I'll leave
you to guess what it was he wanted to "trigger"
Example-B: Poster requesting design help to construct an EMP device to "take out" a 3-square-block
area.

Now you're asking us how to locate a "package" 2 meters underground.
Which Cartel do you work for ?
How long is the tunnel ?

you figured me out

MarkT:
Not enough information I'm afraid - what are these elements? How large can they be? What's the power budget? Are there magnetic materials in the environment? Underground in what material - soil, bedrock, reinforced concrete? What kind of obstacle?

Details will matter, and its a very hard problem. My suspicion is that if the elements can be quite large then
magnetic loop antenna might be a possible method.

The application is to search for a dog who got stuck in a lary burrow. So element A must be small and attached to the dog's collar. Element B can be quite large. I don't care about determining the exact distance, but rather about locating the dog.

, but rather about locating the dog.

And then what ? Do you dig 2 meters down in the ground with a shovel to get the dog out ?

Why not just put leash on the dog's collar and pull him out with that ? (or is the burrow too narrow
for the dog to turn around ?)

raschemmel:
And then what ? Do you dig 2 meters down in the ground with a shovel to get the dog out ?

Why not just put leash on the dog's collar and pull him out with that ? (or is the burrow too narrow
for the dog to turn around ?)

Don't waste your time, please ...

This sort of device might be adapted? Avalanche transceiver - Wikipedia

[ A commercial application of magnetic loop comms AFAICT. ]