What are the white circles before runway holding point? I tried looking on manual but couldn’t find anything
closed as unclear what you're asking by Ralph J, fooot♦, GdD, Sean, Juan Jimenez May 17 at 8:00
Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.
These white circle were also marked with some range and bearing data. That means if your aircraft is in that circle, your vor and dme should read those marked values which in turn help the pilot to check serviceability/accuracy of vor dme. It’s manual version of test Vor to check accuracy of aircraft equipment.
If they look like this one at KSJC [https://email@example.com,-121.9258751,158m/data=!3m1!1e3]
then it is a certified VOR receiver checkpoint. These will be listed in the chart supplement (A/FD).
San Jose (Norman Y. Mineta San Jose Intl) 114.1/SJC G 125 1.4 On runup area Twy W and D.
The Standards for Airport Markings should have information on all markings for US airports. It has this information on the design and dimensions of VOR checkpoints.