[Tagging] Fixed position GPS receivers

[John Smith]

I'm currently going through mapping fixed position GPS receivers that
are used for measuring tectonic plate movements, can anyone think of a
better tag than man_made=gps_receiver ?

It was suggested to mark it as a survey point, but these locations
aren't used for surveying.

http://www.openstreetmap.org/browse/node/739113588

http://www.ga.gov.au/geodesy/argn/sydn.jsp