Precise VOR radials with DME distance using online tools?

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TazzyTazzy

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Mitch
I'm about to do my first real cross country next Wed, with ground school training for it this Sunday and I have a random question. I've flown to a local ATC airport, but it was only a 20 NM travel and another airport 25NM to try and find some wind.

Say I want to fly over a specific latitude/longitude without using the GPS in the plane, but using VORs. Looking at the charts, I can tell that my spot is roughly along the radials of two VORs. ~353 from one, and ~241 from another. However, is there a tool that I can use that would tell me specific radials along each VOR. The plane I'm in has DME, so I could use the VOR radial with DME distance instead right? It's about 24 NM from the ~241 radial.

Just looking to see if there is a more precise method. Perhaps with a PIN drop, and it would tell me the two nearest VORs and their radials or a VOR-DME/VORTAC and it's radial and distance.

I found where I want to go using Google earth, so I was planning to just use the VORs to get me close enough and then just look outside. I was just curious if there is a more precise way.

Thanks.
 
sectional and plotter should do the trick
 
TazzyTazzy said:
I found where I want to go using Google earth, so I was planning to just use the VORs to get me close enough and then just look outside. I was just curious if there is a more precise way.
Click to expand...

There is a more precise way to calculate it. The so-called "Haversine" formula from spherical trig will do it. Google rhumb line navigation and you'll find relatively short implementations (you can use great circle navigation formulae as well -- those are easier to find -- provided the distance is short compared to the radius of the earth; this seems really likely).

You'll need to know the latitude and longitude of the navaid and of the target position.

But, you can't really fly a radial more accurately than about 1 deg. Which will get you within 1/2 mile or so depending on distance (1/2 mile is for 30 miles distance), if your CDIs are rock solid. They often aren't.

The precision for IFR is 4 miles either side of centerline on an airway, presuming the airway is on a VOR radial (most are, but there are some GPS-only airways now). I wouldn't expect much better for a student pilot.

I don't think you're going to do any better than a sectional and plotter, then spotting your landmark visually.
 
tonycondon said:
sectional and plotter should do the trick
Click to expand...

Military pilots flew 600 knot low levels all the time using just a chart and plotter for planning.

But you're welcome to use spherical geometry. Or a sextant. ;)
 
Duats.com can do it. Here's a test I did on it. Departure and destination KFRG, then entered two lat/longs, of 4045/7351 and 41/74. Duats calculates those into LGA/169.3/2.2 and TEB/028.3/9.5 . This seems to do exactly what you want. You could get the lat/longs off of SkyVector by right-clicking, then enter them into Duats without any decimal places.



Code: 
    Ident  Type/Morse Code  |                        | Fuel
    Name or Fix/radial/dist |                        | Time
    Latitude Longitude Alt. | Route   Mag  KTS  Fuel | Dist
---+--------+---------+-----| Winds   Crs  TAS  Time |------
 1. FRG    Apt.             | Temp    Hdg   GS  Dist |  0.0
    Farmingdale NY (Republi |--------+----+---+------| 0:00
    40:43.7   73:24.8    1  | Direct             4.1 |  68
---+--------+---------+-----| N/A     288   80  0:15 |------
 2. Wpt.  113.1/169.3/002.2 | -39C    288   80    20 |  4.1
    LGA    .-..  --.  .-    |--------+----+---+------| 0:15
    40:45.0   73:51.0   99  | Direct             3.3 |  48
---+--------+---------+-----| N/A     348   80  0:12 |------
 3. Wpt.  108.4/028.3/009.5 | -48C    348   80    17 |  7.4
    TEB    -  .  -...       |--------+----+---+------| 0:27
    41:00.0   74:00.0  181  | Direct             0.3 |  31
---+--------+---------+-----| N/A     132  119  0:16 |------
 4. FRG    Apt.             | +13C    132  119    31 |  7.7
    Farmingdale NY (Republi |--------+----+---+------| 0:43
    40:43.7   73:24.8    1  |                        |   0
---+--------+---------+-----|                        |------
 
You can use skyvector.com.

Right click where you want to go, and click "Plan" next to the GPS coordinates that pop up.

In the flight plan dialog, add the VOR itself. The flight plan box gives you distance (over the ground) and your magnetic course (true course in parenthesis). This is essentially your TO radial. Switch the order of the waypoint and the VOR to get the FROM radial.

If you already know the exact GPS coordinates, you can actually enter those into the flight plan box instead of trying to find them on the sectional. I don't all of the formats it will accept, but it works well with decimal degrees, neg/pos for hemisphere, and no space. Example: 43.5630,-120.44
 
Using a tool such as Skyvector.com will give you the magnetic course but that frequently will not be the exact radial as a VOR's declination doesn't usually match the local variation exactly unless the VOR has been recently calibrated.
 
Larry in TN said:
Using a tool such as Skyvector.com will give you the magnetic course but that frequently will not be the exact radial as a VOR's declination doesn't usually match the local variation exactly unless the VOR has been recently calibrated.
Click to expand...

Exactly.

Compare skyvector's mag courses with those printed on the sectional or using the compass roses. They often differ by a few degrees. The difference is mostly "VOR twist," essentially how much magnetic variation has changed since the VOR was calibrated.
 
MAKG1 said:
There is a more precise way to calculate it. The so-called "Haversine" formula from spherical trig will do it. Google rhumb line navigation and you'll find relatively short implementations (you can use great circle navigation formulae as well -- those are easier to find -- provided the distance is short compared to the radius of the earth; this seems really likely).

You'll need to know the latitude and longitude of the navaid and of the target position.

But, you can't really fly a radial more accurately than about 1 deg. Which will get you within 1/2 mile or so depending on distance (1/2 mile is for 30 miles distance), if your CDIs are rock solid. They often aren't.

The precision for IFR is 4 miles either side of centerline on an airway, presuming the airway is on a VOR radial (most are, but there are some GPS-only airways now). I wouldn't expect much better for a student pilot.

I don't think you're going to do any better than a sectional and plotter, then spotting your landmark visually.
Click to expand...
I agree with your conclusion but wanted to point out that VOR radials are great circle routes not rhumb lines. That said, at 30nm from the VOR the difference will be insignificant compared to other errors.
 
Make sure you estimate the radial using the sectional radial circle on the VOR. If you use your VFR plotter to determine the true course and then correct that for the local variation to determine the radial, the radial can be quite different than the plotted value. This is because the VOR radial is based on the variation at the time it was installed or last adjusted and can vary from a current value by 3 or more degrees. I have seen them as much as 5 degrees off.
 
At any distance more than 25nm, finding an exact radial on an OBS is a crap shoot, depending on local conditions and accuracy of your equipment - I've seen days where 70nm was easy and days where 20nm was impossible. Use the VOR intersection for a rough location and local landmarks to fine-tune it from there.
 
Wow. Thanks everyone for the various methods. I've looked at google earth to know what landmarks around my grandmothers house. I'll check out duats and play with skyvector too.

She was born in the house (the kitchen table) and later in life, moved back in after her parents passed away. She stayed there up until the last couple of months of her life, where she moved in to another family members house down the street. Wanted to take a picture of it from up above. The house is still in the family and is one of the largest plots in the middle of the city. It's a small farming town, but it still has history for the family given that some of the streets are named after some of grandma's parents and their siblings. The large lot with the house, barn, shed, etc etc really stand out from the tighter packed in houses. :) Rumor is, someone already had dibs to move in after they retire.
 
Not quite the same question. Isn't there a program that would build radial/distances for using a King 80 RNAV unit to fly a straight course?
 
The old flight guide used to have radial/distance coordinates to the nearest vors in the airport page. After my wife was told by her instructor NO GPS, she tried that trick on the old VORDME-RNAV system her training aircraft had. The instructor caught on quickly and said NO RNAV period.
 
Larry in TN said:
Using a tool such as Skyvector.com will give you the magnetic course but that frequently will not be the exact radial as a VOR's declination doesn't usually match the local variation exactly unless the VOR has been recently calibrated.
Click to expand...

This is true, hence the "essentially" in my post, but the same problem will exist even if you find the course mathematically.

With Skyvector, just as with a plotter and sectional, you can see where the course line cross the compass rose and use that if you believe the twist is significant (as long as the waypoints line up correctly on the virtual sectional).

What would be really helpful is if the VOR calibration was published somewhere, but I'm not aware of a place to find it. Anyone know if there's a way to get that information?

The OP is best off using a smartphone or tablet to navigate there by GPS.
 
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No one believes in pilotage anymore?

When I "need" to fly over someone's place I just use landmarks on the ground to get close. You're better off following a river with your eyes to where it crosses with a railroad track and then where the road curves beyond that, and look for the three red barns instead of looking at your CDIs and then looking outside.
 
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