Marking on charts a symbol for the locations of ATS Area VHF transmitter sites.
I'm interested in the point of this. Why do I care where a ATS VHF transmitter is physically located? What operational decisions do I make on the basis of that information?
There are numerous locations where the marked area freq does not work at lower levels, but knowing where the site was might allow you to communicate with centre on another frequency. Remember, the area freq boundaries are designed mainly for high and medium air routes and sectorisation based on ATC work load and staff availability, not on or for low level GA ops.