[donavanm]

Do you mean survey markers/targets? Theyre used in civil construction etc to track changes relative to an established datum https://www.berntsen.com/Surveying/Smart-Targets-Datums-Refl...

[trhway]

looks like it. There had some time ago been warning that some civil markers may be mistaken for suspicious one, and looks like that is what happening in this case. Sent them email about these ones.