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Btriple7
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The Ghost Of Charles-de-Gaulle

Fri Jun 23, 2006 11:26 pm

I found this interesting picture whilst browsing Google Earth.

It seems like CDG is haunted by a ghostly Thai 747.  scared 
Big version: Width: 736 Height: 659 File size: 114kb
Big version: Width: 736 Height: 659 File size: 108kb
The Ghostly Thai 747 that haunts CDG!!!


I think this effect is caused by some sort of double exposure. Maybe someone who knows a little more about photography can shed some light.

Regards,
Btriple7  Smile
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Spruit
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RE: The Ghost Of Charles-de-Gaulle

Fri Jun 23, 2006 11:30 pm

Great find!

I love these odd glitches in Google Earth and would be even nicer if the Concorde's at Heathrow were still in action as in the Heathrow imagery!

 Smile
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PanAm747
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RE: The Ghost Of Charles-de-Gaulle

Sat Jun 24, 2006 12:46 am

And there I was looking for his nose on one of the images...

I doubt that if that is a ghost that it is Charles de Gaulle...he would NEVER appear in any form that was non-French.

Now, if you come across a Google image of a Dassault Mercure or an Air France Concorde, let me know...  ghost 
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antoniemey
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RE: The Ghost Of Charles-de-Gaulle

Sat Jun 24, 2006 12:53 am

No, no, no... that's just the Thai plane testing out their new phase cloak in time to avoid being whacked in the tail by the Air France jet.  Smile

(If you don't get it, you haven't watched enough Star Trek)
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fbgdavidson
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RE: The Ghost Of Charles-de-Gaulle

Sat Jun 24, 2006 1:17 am

"My first job was selling doors, door to door, that's a tough job innit" - Bill Bailey
 
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antoniemey
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RE: The Ghost Of Charles-de-Gaulle

Sun Jun 25, 2006 12:30 am

Quoting Fbgdavidson (Reply 4):

That thread was fricking hilarious! Thanks.
Make something Idiot-proof, and the Universe will make a more inept idiot.
 
mandala499
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RE: The Ghost Of Charles-de-Gaulle

Sun Jun 25, 2006 4:10 am

Yes it is a double exposure... sort of... This is standard for aerial (and satellite) survey photos.

There is a misconception that all of the photos on google earth are satellite images, some are taken from aerial photographs... and on the aerial photographs, these things happen. So, in aerial photographs, you take lots of small pics of the ground in a series of straight lines. The pics normally overlap 60% along track and 20 - 30% across track, but if you got the money, you do 60% overlap on both the along and across tracks.. The lower you fly, the smaller the area per pic is and you have to take small pics. The reason why you do the overlaps is to make sure you leave nothing behind. The reason why you do 60% overlaps is to do stereography for creating a digital elevation model and orthorectification (ie. eliminating perspectives to get a true vertical view... or nearest to vertical view across the area you surveyed)... nowadays, this can be done automatically... though it eats your processors  Smile

After you take the shots, you then compose an uncorrected mosaic of the area you took to check if the overlaps are good before the real processing begin, which is then to make a geocorrected mosaic to provide an accurate mosaic for an overview of the surveyed area (clients like this!), then you go to the orthorectification and digital elevation modelling.

The standard problem when mosaicing is what do you do with the overlapping areas? Simple, you take the object of interest (land feature) in the overlap area, and then cut the overlap from the edge of the frame you decide not to use. A "bad" mosaicing will leave lots of cut marks allover the place... a good one will give you a seamless image of the land feature without the crop marks or even distortion... and this is before orthorectification!

In the TG and AF 747 pics, obviously the feature that needs to be fixed is the taxiway and not the 2 747s. So, one pic's edge is corrected (stretched, pulled, cropped and whatever else that's required) and if needed (such as in this case), you fade one picture on another.

As of the different locations of the 2 frames taken, you can see it from the perspective angle of the 2 747s. Both aircraft were photographed from the left side. I am guessing that the Thai 747 was photographed from the left front side of the aircraft while the Air France 747 was taken from the left rear of the aircraft... the different nose lengths (could also be caused by mosaicing stretch) and the shape of the engine inlets led me to conclude that (with literally only a finished mosaic to look at which is difficicult)...

Both pictures were taken from the same longitude (standard method, that is to take the same longitude for each n-th number frame along each track) but on different tracks. Tracks run east to west (vv) to minimise aircraft position and track errors due to the earth's rotation... and each track can last for a while (I've made a pilot hand fly for 30 mins in a straight line to keep the wings level, the pitch constant and directional adjustments using rudder,,, it's hard, and not comfortable to be inside the aircraft... unless you have a good autopilot (even better with track function), and a gyro stabilised camera platform with a fast reacting motor and large freedom of movement...)... Some tracks (on autopilot) can go for a VERY long time...

So, it's technically a double exposure... but you know what I mean...
I hope this sheds some light on the occurence...

Mandala499
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hmmmm...
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RE: The Ghost Of Charles-de-Gaulle

Sun Jun 25, 2006 9:17 am

Mandala, why did you have to ruin a good ghost story?
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b52murph
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RE: The Ghost Of Charles-de-Gaulle

Sun Jun 25, 2006 3:59 pm

Quoting PanAm747 (Reply 2):
Now, if you come across a Google image of a Dassault Mercure or an Air France Concorde, let me know...

Odd that our ghost has a shadow...  Smile

Funny...I keep looking for an Eastern L1011 in the photo too, but, alas, Bob Loft and Don Repo haven't graced us with a view of N310EA.  ghost 
 
wrighbrothers
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RE: The Ghost Of Charles-de-Gaulle

Sun Jun 25, 2006 11:22 pm

An interesting find !

Quoting Fbgdavidson (Reply 4):

Oh yeah, one word, muppet  Silly

Wrighty
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SP90
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RE: The Ghost Of Charles-de-Gaulle

Mon Jun 26, 2006 1:02 am

Quoting Antoniemey (Reply 3):
No, no, no... that's just the Thai plane testing out their new phase cloak in time to avoid being whacked in the tail by the Air France jet. Smile

They could save a lot of time by just driving through all the taxiway and ramp congestion and decloak right at the gate!  Big grin