How do I tell where over land an a/c is....

[brockenspectre]

OK..this is going to sound a little weird maybe, but I have a good sense of 3D space and often imagine aircraft in a 3D holo-environment when I am airborne and on frequency (its OK, I am just a private pilot!) - in fact I think ATC of the 21st century should be holo imaging of the airspace under control!

Anyway...... as I sit here, looking westward in SE London at the end of a sunny August day, the sky is still blue and contrails are marking the path of a/c heading to the north/USA and beyond.

A couple just zoomed past - gotta be up at FL390 or better and really motoring and...I was just trying to figure what part of UK they would actually be over as I see them.... just trying to imagine an equilateral triangle from me to a/c and back to ground!!! silly I suppose but...is there a way to figure where an a/c is like this?

::pours second glass of wine and waits for replies::

:D

[bodstrup]

It's 20 years since I had serious math, so I will try a simpler suggestion ;)

Take a chart of high-level airways and use the most probable going in the right direction to get the path over ground.

Then take a bearing to do a triangulation (I assume that you know where YOU are.

The only missing parameter should be the actual FL.

If the aircraft is cruising af FL 300+ and without following an airway, the theory falls short though.. they could go direct to a NATS entry point ?

Regards
Michael

[Agaricus bisporus]

Isn't there a flight tracking website somewhere that shows you the position of all US and perhaps transatlantic flights too?

All you'd need is the flight no.

Failing that if you can either judge the difference between mid level and high level traffic and make an assumption about height, therefore range, or use a bit of aircraft recognition, a table of wingspans and a telescope/bins with an angular graticule you could do the job scientifically. Then measure the angle of the aircraft from the vertical/horizon abd again simple trig gives you an answer.

All the same, it seems a lot of faff just for curiosity.

[PaperTiger]

Flightrackers (www.flytecomm.com etc.) don't give exact positions. Some have a graphic display but the airplane icon is about 100 miles wingspan in scale. Others will tell you how far from destination a flight is and some give height and IAS (TAS ?). Haven't seen any which give lat. and long. so as to pinpint the position. And there's a reporting delay anyway.

[Flying_Tuur]

Well, if you see the aircraft, you can take it's bearing relative to you. Thiw gives you already a line on a map where the aircraft can be, but not an exact position...

If you take a device to measure angles (I don't know the name in English) and you measure the angle of the aircraft relative to the horizon, then you can calculate a rather exact position as follows...

The measured angle is "a", so an aircraft right above you should have a=90°... If you substract a from 90, you get a value "b" between for an aircraft on top of you of 0°, while the horizon is 90° ....

The only 'gamble' we have to make is the actual FL of the aircraft... But if we take an average of about 12km heigth, the outcome won't be too far off...

The distance the airplane is away from you equals: 12km / tg(b)

So if you measure 45°, the distance is about 12km...
If you measure an angle between ac and horizon of 30°, the distance is: 12 / tg( 60° ) = 20.7 km

Although you don't have an exact result, I think you will be close enough... Anyhow, since we travel at about 13 km/min (1,1km / 5 sec ) , we will be already some distance further as you calculate the result...

Hope to have helped you out...

Tuur

[twistedenginestarter]

brokenspectre

What do you mean by 3D holo-environment ?

[Just_Another_PPL]

brokenspectre I was just trying to figure what part of UK they would actually be over as I see them brokenspectre

bodstrup Take a chart of high-level airways and use the most probable going in the right direction to get the path over ground bodstrup


Isnt that just the answer to the question? Where are they over land, just check where the airway is.

Thats it no?

[DrSyn]

Hi, brockenspectre, hope you're well!

The westbounds you refer to are more likely to be in the mid, even low, 30s at your place. However, the actual height is not that important for guesstimations, as they'll all be moving along at around 8 miles per minute anyway. As I know you're more familiar with standard measurements and can read a map, the following rule of thumb will apply to an aircraft at 35,000ft.

(Angle above horizon = Distance)

45º = 6nm
30º = 10nm
20º = 16nm
10º = 33nm

You can estimate angles using a school protractor and noting the angular elevation of local objects such as trees and buldings and using them as markers. Eg, The top of that tree is 45º, the gable of that house is 20º, etc.

Hope that helps.
xxx

[Hippy]

You could do it scientifically, using 'a device that measures angles' or a sextant as we earthlings call it ;) , but you would have to know it's exact altitude, which I assume you don't.

Take it from me, I work at West Drayton and will, every know and then, observe a con-trail out the window in the smokers room and then observe it on radar and am always amazed how close to me it actually is. It can be very deceptive. This is something I learnt from the Met course at Shinfield Park aswell, trying to estimate the height of SC. It is common for humans to over estimate height, because it is not something that we can naturally deal with. Think about it, an aircraft at FL390, observed at a 45deg angle is about 14Km / 8.5 miles away, allowing for reduction in air density at altidude. Or, if you're sitting in Blackheath enjoying that fine Shiraz, they are over Fulham wrestling with the rubber chicken. :D

Looking at an air chart won't help, because in that area they are rarely on an airway centre-line anyway.

Hope quriosity is quenched and you can now return to the grape, I know I am ;)