Working prop stalker style echo detector/ beeping item locator

Hello,

I need some help/suggestions with building a working echo detector for airsoft role playing game in stalker fashion.

In short- there will be rare artefacts scattered in a 3 km territory and and echo detector stars beeping when the artefact is close, and starts beeping more intensely when getting closer.

Please suggest what parts and logic should use to create this? maybe theres a similar project that you could link me to? i couldnt find anything useful on instructables, but i guess my searching skills have abandoned me, like hair from my head :smiley:

As this is a 3km territory it must be outside so gps trackers on the artifacts and a gps on the detector?
A much cheaper solution would be to just record the gps coordinates of each artifact and have a gps receiver in the detector, it would bleep as its position neared one of the recorded ones.

I don't know if this is an urban legend or not but I seem to recall Russians making either banknotes or bibles radioactive so that they could track those handling them - a bit of an extreme solution for a game though.

the artefacts should be located from like 1 km away. it should start beeping only when it gets 10-20 meters close. We do not need to know the exact location of the items (although the organisers of the event know exactly where). We just get hints where to look, and hope for the locator to beep

I found out that ESP8266 module can detect open hotspots and act as hotspot. i guess i'll try fiddling with the code to make it work like that

Trop:
the artefacts should be located from like 1 km away. it should start beeping only when it gets 10-20 meters close. We do not need to know the exact location of the items (although the organisers of the event know exactly where). We just get hints where to look, and hope for the locator to beep

I found out that ESP8266 module can detect open hotspots and act as hotspot. i guess i’ll try fiddling with the code to make it work like that

You could do that butthen you need every artefact to be fitted wih an ESP8266 and the detector needs to identify only hotspots that are associated with an artifact.

If instead you put a gps in the detector the organisers simpy load the artefact co-ordinates into the detector (you cannot see them) and the detector bleeps as soon as it nears the location of an artefact.