Air Traffic Controller Discussion With a Global Perspective
By Neil Farrington 1104841
#457693
Adam Lagoda 827397 wrote:Thanks Neil for your answer, and sorry if my English is out of standards - I've been using this mostly with european teams, and - as you probably know - European English is nowhere near English English standards :P

So, there are no separate ranges for scope and radio? If so, that's confusing. In Poland, there's a station at Modlin (TWR), using the very same frequency as Bremen (the B part). As Modlin is more or less 300nm from the pl-de border, one would assume they will be completely independent. But what we learned from those few times Modlin was manned and Bremen online - they're not. I was thinking it's some misconfiguration problem rather, than anything else. However, how could two stations affect each other with such a large separation? Hmmm. No idea now. TWR would be easily idetified as source if range was too large. And I can hardly think of CTR working with range 250nm beyond own borders.

Not at all, your English is perfect, it's just not the easiest of topics to explain.

No, there are no separate ranges for scope and radio - they're both related to the set visibility range on the client.

As Bremen Radar is a CTR position, they can often have a high vis range of 300nm+, and of course, some controllers also overextend. The distance between Bremen and Modlin is 400nm-450nm, so really, all it would take is a 400nm vis range for the positions to overlap, on top of any additional range added by the pilot client.

The next time it happens, you could do a little investigating:
For the purposes of obtaining the required information, you will need to use VRC (for the additional information it shows). In the controller list, find Bremen and Modlin, and check their vis ranges as shown by VRC. Then right-click in each, and select 'Show Location' - this will show where their primary vis point is set, and their vis range. This will allow you to visualise the overlap, and see how close they are.

At the end of the day, the overlap itself won't be the issue - aircraft near to Modlin and further east will only pick up Modlin, and aircraft nearer Bremen and further west will only pick up Bremen. The problem area will be directly in between, where the pilot client is between the vis points and picks up both stations.

Generally, it's unusual for this to happen, as most countries ensure that centre positions have different frequencies to local positions due to overlap, but because VATSIM works a little differently to real world, we do get this overlap sometimes.
By Ross Carlson 887155
#457694 Unless things have changed since I last looked at the server code, there are separate range values in play for radio versus radar. The visibility range that the user sets in the client affects only radar range. It determines the radius within which the server will send you target position data. So, it determines which blips you see on the scope.

Your radio range determines which pilots (and other controllers) see you on their controller lists. Radio range is independent of visibility (radar) range and the visibility range setting has no effect on radio range. Radio range is determined by the server based on the facility type you sign in with and it is a fixed value. I can't remember the exact numbers, but it's something like 5 for GND, 25 for TWR, 100 for APP, 400 for CTR, etc. (Again, those are just guesses to illustrate how it works ... they are not necessarily the real numbers.)

It's important to note that radio range for controllers is fixed (as described above) but it is dynamic for pilots, since a pilot's radio range is a function of altitude. The server determines whether or not a pilot should see a controller in his controller list by determining the pilot's radio range (using altitude) and checking if that range overlaps with the controller's range. So a pilot on the ground 450 NM from a CTR controller may not see that controller, but that same pilot at 35,000 feet (still 450 NM from that controller) will see that controller, because at that altitude, the pilot's radio range is much larger, and will thus overlap with the controller's 400 NM range. (On a side note, this calculation uses the pilot's altitude MSL, not AGL, so a pilot on the ground at Denver has a much longer radio range than a pilot on the ground at Boston. :))

To confuse things a bit, while the visibility range has no effect on radio range, the visibility points do have an effect. When making the above determination as to whether or not a pilot should be able to see a controller in his controller list, the server does the overlapping range check once for each of the controller's visibility points. (Same for checking if controllers can see each other.)

Summary: Visibility range affects only target visibility and is set by the controller. Radio range is not affected by visibility range and is a fixed value for controllers, and a dynamic value calculated by the server for pilots, based on altitude. Visibility points apply to both.

Again, this may have changed since I last looked at the server code, which was a few years ago.
By Neil Farrington 1104841
#457695
Ross Carlson 887155 wrote:...

I've done a fair amount of late night controlling in the past, and given that I am the only position online, I often get pilots from airports a number of miles away calling me up, and very occasionally, a new pilot who ends up keying up on frequency and continuously transmitting. While I try and help them fix whatever problems they're having, I tend to reduce my vis range away from the aerodrome they're at, so that they drop of my frequency, and I don't get a 4AM earache.
Given that they do drop off my frequency after the vis range updates, this is my basis for audio being connected to the visibility range, rather than the station type.

The server using altitude to determine a pilot's vis range in terms of controllers in range is news to me, though - I would have assumed this would be the same as what is set by the pilot client.

Edit: Although, that said, I often have multiple vis points set myself, so I may be struggling to remember whether it's lowering my vis range or removing the additional vis point that does cause them to drop off.
By Miguel Frias 1107190
#457696 It will most certainly be removing a vis point.

In LPPC for instance we have a special "X" waypoint that was calculated as the mean point, the center point of the FIR. However, by as low as about 20nm, We need an extra visibility point to get the farthest northeastern traffic to see us as a controller (radio range). While my range is 600nm, they cannot tune into my frequency. When I create a second point, it extends the radio range to the intersection of both circles, hence allowing for the pilots to tune in. If I remove that second visibility point, they'll drop off from frequency, sure thing.
By Ross Carlson 887155
#457720
Adam Lagoda 827397 wrote:Thanks for confirmation. Is that also centered around visibilty points? Hopefully, this is the solution then - to properly use vis1..vis4.


Yes, both your visibility range (radar range) and your radio range are centered on your vis points.
By Adam Lagoda 827397
#457759
Miguel Frias 1107190 wrote:It will most certainly be removing a vis point.


Miguel, your guess was right :)
Yesterday I managed to run some checks. On standard, both stations do not interfere (with quite a margin, I moved my vis2 from Mofdlin to Poznan, by nearly 200nm with no effect). However, if station Bremen A serves as B as well (to provide ATC on all areas of ATC zone which is more-or-less rectangular with width twice as big as height), it's quite usual for them to set up another visibility point over eastern Germany, and that's most likely causing the problems.
We'll work together with German ATCs to see whether it can be solved by small steps.

Thanks everyone for your help, the knowledge here (and on thread pointed out by George, thanks mate) is invaluable. Appreciate your help, really.

Have a nice day all of you.

Adam
By Roland Collins 800023
#457769 It is worth mentioning that if you temporarily change your vis point it affects your visibility; which means to some aircraft and controllers you seem to have suddenly logged off.

In VRC if you change your view by RMB dragging or by using “.centre” is does NOT affect your vis point and how others see you. If needed you can set up another vis point, of course.

Roland Collins
By Bradley Grafelman 1242018
#457770
Roland Collins 800023 wrote:In VRC if you change your view by RMB dragging or by using “.centre” is does NOT affect your vis point and how others see you.
... unless, of course, you forget to set a fixed vis point after you open VRC since, for whatever reason, visibility points are not saved in session profiles.
By Bradley Grafelman 1242018
#457773
Roland Collins 800023 wrote:The default vis point is usually defined in the sector file; well at least it is in all sector files I've worked on and defining one is certainly best practise.
Er... best practice? Even though there could be hundreds of positions in a given sector (from DEL on up) and one vis point to rule them all?

At any rate, there is no default vis point in the sector file - only a default center point (which is ignored once you save your own session profile). Without doing a ".vis" after opening VRC, you have a floating vis point that follows the center of your scope.
By Mike Evans 822396
#457780
Roland Collins 800023 wrote:The default vis point is usually defined in the sector file; well at least it is in all sector files I've worked on and defining one is certainly best practise.


That point is an arbitrary point to define the "center" of the sector.. I know ASRC never used it to set a vis point, I'm fairly certain VRC doesn't either..
By Ross Carlson 887155
#457781
Mike Evans 822396 wrote:
Roland Collins 800023 wrote:The default vis point is usually defined in the sector file; well at least it is in all sector files I've worked on and defining one is certainly best practise.


That point is an arbitrary point to define the "center" of the sector.. I know ASRC never used it to set a vis point, I'm fairly certain VRC doesn't either..


It doesn't ... though it does set your scope center point to that point when you first load a new sector file, and your center point is your visibility point until you set one with a dot command.