Plot a VOR Bearing

[David Taylor]

Tablet navigation is pretty dependent on GPS.  Pick your favorite doomsday scenario (solar storm, national insurrection, spoofing) and you get a challenging navigational situation in limited visibility.  GPS represents a fairly critical single point of failure.  If only there was another system...

With a paper chart and a straight edge, one could plot a pretty decent position with a couple of VOR bearings.  That's pretty hard to do on the tablet.  Yeah, there's the drawing interface, but making a good straight line is nearly impossible.

Would there be value in a widget to assist with plotting VOR bearings?  I envision the user would enter two bits of info from the plane's VOR receiver: an identifier and a bearing.  Avare would look up the identifier in its database to fetch the VOR's position and variation, then draw a line on the chart of some length extending from the VOR's position.  Add a means to plot 2 or more bearings and you get a position.

In a DME equipped plane, additional input might be distance and altitude.  The app could use those to compute ground distance and plot a position with only one bearing.

Sounds worthwhile to me.  What do you think?  I suppose this has all been discussed previously. (I'm a backend dev, so this sort of work gives me the squirms.)

Dreaming further (more in my own wheelhouse)...  I was poking around a SDR  project site and found a library that some fellow wrote to decode VOR signals.  The input is the signal stream. The output is a bearing.  I'm thinking: integrate that library in something like a Stratux box with an additional SDR or two, write a service that continuously scans the known VOR channels and mix in a Morse decoder.  That enables the service to automatically publish identifier/bearing data with zero user input.  Next, extend the Stratux plumbing and include it in the data feed to the EFB.  Now you potentially have backup position data, totally _independent_ of GPS and requiring no fiddling around with entering frequencies, twiddling the OBS and getting confused with from/to.  Lower workload = longer piloting life.

[Jeffrey Ross]

The whole world is pretty much dependent on GPS not just Aviation plus I don't think the Avare forum is the right place to argue the merits of using GPS as the primary or sole form of navigation.  To make matters worse VORs are disappearing at an alarming rate, just look at your preflight briefing listing all the VORs that are OTS either temporarily or permanently, I swear the list is growing by the minute.

Remember in VFR you still have pilotage available to you to identify your location and you can fly via dead reckoning it's the IFR guys that have more of an issue as ATC simply assumes you have GPS.   This all goes back to what type of flying you do and how you use Avare in your flying and as I've learned everybody's mission is different and you ask 10 users of the software and 10 users will use it differently.

I still have 2 (working) VOR receivers in my aircraft and I'll be honest with you, I'm not sure I know the last time I actually navigated using one for anything other than flying an ILS/LOC, yes I've done VOR checks, but even there I question the requirement as it is only required if I plan on using them for IFR flight.

In terms of adding VOR receiver capability to the Stratux software it sounds like you are looking to create a "VOR/DME RNAV" system,  I would think this would be a very large undertaking for for a system that is rapidly being decommissioned.  However if it is something you think would be valuable I'd suggest reaching out to the Stratux development group, I'm sure they have a forum someplace.

Oh and a final two words, should you ever be navigating via GPS and military interference testing becomes a safety of flight issue, you can always call out to ATC "STOP BUZZER!"

Jeff

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[David Taylor]

Oh yes, I realize we're "all in" on GPS dependency.

While VORs are disappearing left and right, the FAA recognizes there must be an independent backup system (google "vor minimum operational network").  So, I think some VORs will be around for the foreseeable future, especially in the western US, where I fly.

Thus, I continue to have a hankering for a tool to plot bearings on the electronic chart.  After a self-guided tour of Avare's GUI code, I can see that it's a doable task, but certainly non-trivial.  Maybe I'll take a whack at it one day.

...and the extension to Stratux: total pipe dream. I put it out there merely as a seed, that may find fertile ground one day...

[Jeffrey Ross]

how about doing something like this in the flight plan area?

KEWR SAX SAX275020 KAVP

where SAX is a VOR and SAX275020 means SAX VOR 275 radial 020nm DME

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[David Taylor]

Hey, that's pretty nifty coordinate transformation feature.  Using the plan tool a little clunky for plotting more than one bearing, and not compatible with an active plan... but could be helpful as is.  Thanks for the pointer!

[Peter Gustafson]

This is actually not as hard as it may seem.  I had some students put together a VOR receiver based on a software defined radio.  It is something a good coder could do with a little hardware... unfortunately students graduate and projects languish.  My own skills in python have improved immensely since that project began.  IF I can find the time I'll take a stab.

I personally think its value would be as an emergency ILS display.  The ILS system isn't going away any time soon.

[t v]

Hi.

.. decent position with a couple of VOR bearings????  TV

[David Taylor]

Can you be more explicit regarding what needs clarification?

Most of the planes I rent lack functioning DME.   Therefore, 2 or more VOR bearings are required to produce a position (assuming I'm ignoring signals from space).

PHAK, 16-22:

"The course or radials projected from the station are referenced to MN. Therefore, a radial is defined as a line of magnetic bearing extending outward from the VOR station."

PHAK, 16-28:

"A VOR radial alone merely gives line of position information. With DME, a pilot may precisely locate the aircraft on a given line (radial)."

[t v]

Hi.

... 2 or more VOR bearings...??? TV

[Simon Roberts]

More bearings reduce the error...

Not that one often has the chance to get more than two, and not that one often cares about that level of precision when doing this kind of operation!

[Brad Walker]

Agreed!

When I fly across the US, I always use VORs to pinpoint my position. Even in the rugged western US, I can usually get 2 VORs..

-brad w.

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[Jeffrey Ross]

This isn't something I've done since working on my private pilot cert when the instructor would say "show me were we are on the chart using VORs"  With VORs disappearing and others "temporarily out of service" at an alarming rate the number of VORs that will remain in service will be what the FAA considers a bare minimum to maintain VOR navigation (for now).  GPS has obviously become the primary mode of navigation, and in the IFR world it is almost but not impossible to fly without one as ATC pretty much assumes you are GPS equipped.  Other than tuning in an occasional VOR just to make sure the receiver is working properly, I don't remember the last time I actually navigated using an actual VOR signal.  It has been even longer for the ADF, so much so I just pulled the ADF receiver out of the aircraft last week, guess I'll have to find another way to pick up AM radio to listen to a ball game.

Ok that said now that I understand what you are looking to do, the only way I can envision this being done in Avare is to essentially duplicate what you would do on paper charts which is to draw a line from each of the two VORs you are triangulating your position from.  From the main screen with your chart up, tap the "Pan" button, this will allow you to draw directly on the screen, draw a line from the first VOR matching the radial you are on, then do the same with the second VOR.  You should be able to then zoom in or out of the screen by going back to the "Pan" screen.  When you are done go back to the "Draw" screen and press clear to remove your lines.

Of course the accuracy of your position will depend upon how carefully you draw your lines along with the accuracy of the VOR receiver(s) and how quickly you can get those lines drawn, even a Cessna 150 is doing roughly 1.5 miles per minute....  As the saying goes, measure with a micrometer, draw with a crayon, and cut with an axe.

I usually use the draw option to circle a specific procedure on a plane, for example on a departure procedure I'll circle the instructions for the specific runway I'm departing from.

Jeff

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