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Flight Routing Trails

A place to chat and discuss everything and anything thats NOT Military Aviation related. No Civilian Aviation content please. We would be grateful for such inclusions on our sister site - Civilian Aviation.
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raptor9
Posts: 1552
Joined: Sun Jan 20, 2019 10:52 am

Re: Flight Routing Trails

Post by raptor9 » Thu Apr 07, 2022 6:00 am

Possibly not long enough to benefit them, or maybe the routes are too numerous and busy. I suspect the latter.

iainpeden
Posts: 1054
Joined: Fri Sep 09, 2011 7:20 pm

Re: Flight Routing Trails

Post by iainpeden » Thu Apr 07, 2022 7:30 am

Computer screens are flat?

Same problem with paper maps on a table.

gyvespa
Posts: 473
Joined: Mon Oct 05, 2009 4:49 pm

Re: Flight Routing Trails

Post by gyvespa » Thu Apr 07, 2022 3:17 pm

I looked into this ages ago.
Maps verses globes and all that.

It’s not that easy to explain but this link might help.

https://www.scienceabc.com/social-scien ... -maps.html

A picture is worth a thousand words as they say.
Some of it is related to distances as well. Europe isn’t really that big. Whereas the US is quite a way away. I seem to recall that transatlantic routes don’t just follow the curve they also ‘hug’ the land masses for diversionary purposes.
Just in case as they say.

roger4
Posts: 787
Joined: Mon May 21, 2012 8:09 pm
Location: 1 mile from Benson

Re: Flight Routing Trails

Post by roger4 » Thu Apr 07, 2022 4:34 pm

The aircraft in reality are flying straight lines all the time (shortest distance) whether over land or over the ocean. But the map projections we use to show the world in 2D distorts reality. While north-south routes will accurately show on screen as straight lines, those with a component of east-west will show falsely as curves.

For example, I have just watched RYR96QH (EI-DPH) which passed over me short while ago inbound to Bristol from Bergamo. Following it on ADSB, the initial route out of Bergamo was due north, and hence no curvature was seen on screen. It turned NNW approaching Stuttgart, then WNW just past Brussels, then due west from the Thames Estuary. The legs between VORs (or reporting points) after Stuttgart are each slightly curved as expected, but you may need to do as I did to see it: zoom in on each leg individually and hold a ruler against the screen to see the very slight curvature. They are following great circles, it's just that each leg is too short at 100-200 miles or so to see it easily.

Over the ocean, there are no VORs, so they route via longitude/latitude pairs (e.g. 55N/20W to 55N/30W to 55N/40W ...etc). As a result they follow great circles for long periods (1000 miles plus). Hence the curvature is readily seen even when zoomed out.

roger4
Posts: 787
Joined: Mon May 21, 2012 8:09 pm
Location: 1 mile from Benson

Re: Flight Routing Trails

Post by roger4 » Sat Apr 09, 2022 8:44 am

Thanks for the nice clear examples.

The dotted lines on ADSB Exchange over the oceans are not true tracks based on ADSB signals from the aircraft, as the aircraft are too far out at sea to be picked up by any receiver on ADSBX's network of enthusiasts sharing their data received at home. Instead the ADSBX software plots an estimate of what the track might have been based on known last position. I have no idea why some of these plot some as straight lines and some as curves, on essentially the same route (pictures 1 and 3). But it has to be a quirk of the software. I presume the same would be seen over large tracts of land without enthusiasts sharing their home ADSB data, like the Sahara and the Oz outback!

Hence I think the best course of action is to assume that more than about 200 miles from any receiver, the plots are at best misleading, and at worst complete fiction.

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