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How do they do it?

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How do they do it?

Old 11th Oct 2021, 10:25
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How do they do it?

I've been watching flightradar24 for the last 20 or so minutes, specifically a King Air doing some kind of survey over Exeter. Where it matters, It is being flown with incredible accuracy. I realise that GPS/automation/etc is driving things, but I still find it amazing. Any enlightenment from an expert would be interesting. And why is this kind of work still needed when we now have satellite cameras with 10cm or less definition? Don't we?

Sorry about the aviation content, but it's a choice of JB or Spotters.....
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Old 11th Oct 2021, 10:43
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Possibly because clouds can get in the way of Satellites and they need moving to look at different points on the earth i would imagine thus burning fuel. They normally update areas if there are new roads, or construction taking place.

It will probably be RVL doing the work.

https://www.rvl-group.com/
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Old 11th Oct 2021, 10:46
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Originally Posted by NutLoose View Post
Possibly because clouds can get in the way of Satellites and they need moving to look at different points on the earth i would imagine thus burning fuel. They normally update areas if there are new roads, or construction taking place.

It will probably be RVL doing the work.
It'll be photogrammetry work for the likes of Apple/Google for their 3D maps...
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Old 11th Oct 2021, 11:28
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Many thanks, both. That answers what it's all about. But how the hell do they manage such precision? As far as I can tell there's a variable light north-westerly wind blowing, which can't make it any easier even though the tracks are NW/SW.
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Old 11th Oct 2021, 11:45
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Originally Posted by NutLoose View Post
Possibly because clouds can get in the way of Satellites and they need moving to look at different points on the earth i would imagine thus burning fuel. They normally update areas if there are new roads, or construction taking place.

It will probably be RVL doing the work.

https://www.rvl-group.com/
They would not likely move the satellite, they are in polar orbits, or at least high inclination, and get global coverage over a period of time. That’s the problem there is no guarantee of no cloud cover when it passes over a given location. When ever I have seen Raven doing this it’s on a gin clear day, they have the flexibility to go out when the weather is suitable.
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Old 11th Oct 2021, 14:38
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Probably the Russians taking side on photos of Salisbury Cathedral...
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Old 11th Oct 2021, 14:51
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I assumed the were using Lidar for the 3D imagery but apparently not. Remarkable! Particularly as my neighbour's house has scaffolding around the back and most of the side but none at the front - all erected/struck inside half a day either side of his new roof being done. The roof is still the old one...
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Old 11th Oct 2021, 15:18
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Originally Posted by old,not bold View Post
Many thanks, both. That answers what it's all about. But how the hell do they manage such precision? As far as I can tell there's a variable light north-westerly wind blowing, which can't make it any easier even though the tracks are NW/SW.
Light winds won't effect an aircraft flying on Autopilot on a GPS based flight plan.
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Old 11th Oct 2021, 19:30
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All the more remarkable, because my neighbour has their original roof as well.
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Old 11th Oct 2021, 19:34
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ONB,similar system to ag-flying/tractor GPS ;set spacing for track,then turns,let autopilot do work,have coffee,lots,and plenty of `empties..`
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Old 11th Oct 2021, 21:48
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Navigating the U2 on load from NASA for the detection of the Cosmic Microwave Background could not make use of the data going into the autopilot because it wasn't accurate enough. IIRC they used another background frequency to navigate for the CMB detection.

Last edited by Loose rivets; 13th Oct 2021 at 23:51.
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Old 11th Oct 2021, 23:10
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Loose Rivets, is your inbox full re: private messages?
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Old 12th Oct 2021, 09:55
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Originally Posted by Nige321 View Post
It'll be photogrammetry work for the likes of Apple/Google for their 3D maps...
Too expensive to cover the whole country for them.

It's topographical - ground cover mapping for planning 5G radio sites
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Old 12th Oct 2021, 10:06
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Originally Posted by old,not bold View Post
Many thanks, both. That answers what it's all about. But how the hell do they manage such precision? As far as I can tell there's a variable light north-westerly wind blowing, which can't make it any easier even though the tracks are NW/SW.
I don't specifically know about them but it would be like hand flying a GPS ground track and drape showing on a specific screen in the cockpit. Sort of a very accurate ILS per see but going horizontally and usually following the ground taking into account the aircraft's performance on one engine (If done at low altitude)

It's very precise and surprisingly easy to stay within a few meters cross track.

Same principle with Ag flying except no need of a drape, just a cross track bar shown by a set of green or red lights instead of numbers. In Ag, the screen would be outside the cockpit directly on the nose (So your eyes don't have much of a focus to do)
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Old 12th Oct 2021, 10:09
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Originally Posted by sycamore View Post
ONB,similar system to ag-flying/tractor GPS ;set spacing for track,then turns,let autopilot do work,have coffee,lots,and plenty of `empties..`
Thank you for that which clears it up comprehensively. I'm wondering, though, whether the waste product from all that coffee is dumped while airborne rather than removed after landing. The sortie seems to have been carried out at around 2,850 ft (AMSL? above GPS datum?) so I guess/hope the product would disperse into a thin mist before hitting the ground. As I recall the various (older, like me) Kingairs/Queenairs I've been in, ie B80/90/100 and the 200, the lavatorial facilities were quite basic in most of them, if they had any at all..
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Old 12th Oct 2021, 17:48
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If they had dropped Window when they started the straight bits it would have been the same as the RAF was doing opposite Calais in June 1944.
It gave the impression of an advancing invasion fleet on radar.
All done with dead reckoning
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Old 12th Oct 2021, 22:42
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All done with dead reckoning
They had a little more help than that - all the aircraft had either 2 Gee sets (Operation Taxable) or a Gee and GeeH (Operation Glimmer) on board, with 2 (or 3 for the latter case) navigators aboard each aircraft to ensure that they kept their tracks accurate.
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Old 12th Oct 2021, 22:52
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visibility3miles, I've sent an email and looked at the first review of the book you referred to. Life is full of surprises, and indeed, disillusionment.
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Old 13th Oct 2021, 08:28
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Originally Posted by pilotmike View Post
All the more remarkable, because my neighbour has their original roof as well.
Bloody typical, you invest in a nice new roof and Google shows the horrid old one. Looking at Bing yesterday and my new roof which was done last November is resplendent in the sunshine.

Bing's Streetside images is 10 years old though, but that is useful as it shows new gas main being installed - I've been advised to complain to SGN about the work they did replacing my supply at the same time as it wasn't done properly - useful to be able to date it precisely!
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Old 13th Oct 2021, 09:03
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Returning to the Exeter operation and others like it, any minor drifts from the track will be resolved later when the parallel image strips are all pasted together by computer imaging.
The entire image is then located accurately by reference to known fixed points on the ground.
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