9
$\begingroup$

I do not understand when the Compass around a VOR is and is not present on maps.

For example, around Kansas City:

  • VOR OJC has been deactivated for quite some time now. But its compass is still present on the latest map revision. (the frequency has hash-marks through it, indicating the deactivated status.

Why hasn't the map been updated to remove the compass?


  • VOR RIS is still active, but does not have a compass around it.

Why isn't the compass on this active VOR?

Are there any general guidelines for when a compass is present on the map?

$\endgroup$
5
$\begingroup$

See the Interagency Air Cartographic Committee (IACC) Specifications:

[IACC 2] 3.9.3.8 Compass Roses

Compass roses, as illustrated in Appendix 6, shall be shown centered on all VHF NAVAIDs, when space allows.

Preference shall be given to those serving enroute functions or located in areas not served by other VHF NAVAIDs.

[IACC 5] 3.7.4.5 Compasses Roses

Compass roses shall be charted centered on those NAVAIDs which have routes predicated on them. Compass roses may be shown around other NAVAIDs where placement of the compass rose does not create additional unnecessary clutter or congestion. If compass roses overlap and congestion hinders readability, the compass rose of the NAVAID with the most congestion may be deleted. Compass roses shall be shown oriented to slave magnetic North. Cardinal direction values shall not be shown. Compass roses shall be .75" in diameter and in very congested areas may be reduced in size to .5" in diameter.

In groundschool I was taught that this is actually based on VOR service volumes (which otherwise aren't explicitly marked at all on VFR sectional charts): the compass rose is not shown around VORs with Terminal service volumes. This might be a general rule, but it is not entirely true however. You provide a perfect example: OJC and RIS are both Terminal VORs.

The key differences: 1) OJC has the V10-12 airway, and 2) map is more congested around RIS.

$\endgroup$
1
$\begingroup$

In the case of OJC you can see that the frequency has hatching through it denoting that it has been shut down. However you also see a 77 that is not hatched out. This denotes the units TACAN channel (making it a VOR-TAC facility). Although TACAN is mainly a military technology some civilian aircraft are equipped with it. As such the VOR facility may have been shutdown but the TACAN equipment is still up and running thus the compass around it remains.

For VOR RIS the compass may not be present due to clutter. In some cases things are omitted from VFR maps to reduce clutter. You can find some discussion in this thread here. It seems that in some cases its up to the discretion of the cartographer.

$\endgroup$
1
$\begingroup$

Why hasn't the map been updated to remove the [OJC] compass?

According to the FAA's chart users guide:

NAVAIDS in a shutdown status have the frequency and channel number crosshatched. Use of the NAVAID status “shutdown” is only used when a facility has been decommissioned but cannot be published as such because of pending airspace actions.

Of course, that just changes the question to "what are pending airspace actions"? But the A/FD entry for OJC says it isn't a VOR but rather a VOR/DME:

(T) VORW/DME 113.0 OJC Chan 77 at Johnson Co Executive. 1034/6E. VOR dcmsnd: DME still operational

So the DME portion of the VOR/DME is still active, even if the VOR itself has been decommissioned (and as @Dave pointed out in his answer, you can also see on the chart itself that the DME channel isn't crossed out). I had a quick look at some of the instrument procedures around there and couldn't immediately see where the DME is used, but presumably someone needs it for something, at least for now.

Why isn't the compass on this active VOR?

Most likely because the map is simply very cluttered at that point; the TEB VOR/DME is another example where there's no rose on the VFR chart (although there is one on the TAC). The LGA and JFK roses already overlap there and adding TEB as well would be quite messy.

I found some discussions online that said a) only terminal VORs may not have a rose; and b) including the rose or not is the chart designer's decision. But there were no sources quoted for either statement.

$\endgroup$
  • 2
    $\begingroup$ I can verify that the OJC VOR is not only shut down but disassembled and removed and the DME is still there. Drove by there a while back and the VOR was in pieces and it appears that they moved the DME a couple hundred yards to the east (unless that's where it was to begin with, I'd never noticed it before). $\endgroup$ – TomMcW Dec 30 '15 at 20:07

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.