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Weird 747 shadow

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nico(at)cybersuperstore.c
Guest

Posted: Tue Aug 28, 2007 5:43 am Post subject: Weird 747 shadow

Look at google earth at this location: 26 02 03 S, 28 14 04 E  

   

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John Vormbaum

Joined: 21 Aug 2006
Posts: 273
Location: SF Bay Area, CA

Posted: Tue Aug 28, 2007 9:14 am Post subject: Weird 747 shadow

Nico,



All I see there is a location between Pretoria and Johannesburg, of  a 

house with a pool.....no shadow on my version.



/J



nico css wrote:

 	  Quote: 	
		  

 Look at google earth at this location: 26 02 03 S, 28 14 04 E



  



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bowing74(at)earthlink.net
Guest

Posted: Tue Aug 28, 2007 9:22 am Post subject: Weird 747 shadow

I see the shadow you're talking about but haven't an explanation for it.  It

is a 747-400 in a left turn.



bilbo



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steve2(at)sover.net
Guest

Posted: Tue Aug 28, 2007 11:14 am Post subject: Weird 747 shadow

I have a 'possible' explanation for this. The Google Earth imagery are not

conventional photos, but 'orthophotos'. That is the image is composed of

zillions of photographs that are mosaicked together, and processed to

correct them for tip and tilt of the camera, and to correct the scale of

images versus the variations in height of the land. Lots of other stuff gets

done to the images.....



I'm actually processing an orthophoto right now at work. (I'm hard at work,

honest.)



The ortho images have a lot of blending and processing done to them to have

them look any good across seams, and to correct for vignetting and uneven

tone across them. Its quite a trick to get all these images to look any good

all stuck together at once.



It is possible that the 'weirdness' is due to a computer algorithm doing its

best to make sense of this little image patch, and lighten up a dark area,

and darken up a bright area.



Or it's something else.



Steve



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nico(at)cybersuperstore.c
Guest

Posted: Tue Aug 28, 2007 12:56 pm Post subject: Weird 747 shadow

John,

Did you copy and paste the coordinates into google earth? It should be on

the edge of a suburban neighborhood.

Nico

--

nico(at)cybersuperstore.c
Guest

Posted: Tue Aug 28, 2007 1:14 pm Post subject: Weird 747 shadow

Thanks, Steve. That makes the most sense.

Nico

--

John Vormbaum

Joined: 21 Aug 2006
Posts: 273
Location: SF Bay Area, CA

Posted: Tue Aug 28, 2007 1:40 pm Post subject: Weird 747 shadow

That time it worked....and that is quite the funky shadow/airplane.



nico css wrote:

[quote] 



 John,

 Did you copy and paste the coordinates into google earth? It should be on

 the edge of a suburban neighborhood.

 Nico

 --

andrew.bridget(at)telus.n
Guest

Posted: Tue Aug 28, 2007 4:05 pm Post subject: Weird 747 shadow

> Look at google earth at this  location: 26 02 03 S, 28 14 04 E

 Yes, very interesting - note that the ghosted image  is above the 'clear' 747 - I wonder if it has something to do with a second  photo taken immediately after the first; the 747 having moved on since the  first? I'm sure there's a better explanation...

  

 God bless,

 Andrew

    [quote][b]

nico(at)cybersuperstore.c
Guest

Posted: Tue Aug 28, 2007 4:23 pm Post subject: Weird 747 shadow

Hi Andrew.  

I don’t think so, because the 747 would have to have drifted south without any forward movement. The shadows of the surrounding structures indicate that it’s early morning, so in that respect the blue shadow is in the right place. What is a bit off, I would say, is that the shadow indicates that the sun is slightly south of the 747, which is impossible seeing that Johannesburg is 26 deg south and the sun never gets further south than 23.5 deg. However, if the shadow was moved due to manipulation of the satellite photographs, then it might not show where it actually was.  

Steve gave an excellent explanation: satellite photos are not regular photos but orthophotos, which are programmatically manipulated to make the individual satellite images fit seamlessly in one image, and perhaps some shift could have changed the color of the shadow.  Steve I apologize if my paraphrasing what you said has lost the message.  

Who knows, but it is very interesting.  

Nico  

   

         

  

From: owner-commander-list-server(at)matronics.com [mailto:owner-commander-list-server(at)matronics.com] On Behalf Of andrew.bridget(at)telus.net

 Sent: Tuesday, August 28, 2007 5:05 PM

 To: commander-list(at)matronics.com

 Subject: Re: Weird 747 shadow  

  

     

 	  Quote: 	
		   Look at google earth at this location: 26 02 03 S, 28 14 04 E  

    
	


Yes, very interesting - note that the ghosted image is above the 'clear' 747 - I wonder if it has something to do with a second photo taken immediately after the first; the 747 having moved on since the first? I'm sure there's a better explanation...  

    

   

    

God bless,  

    

Andrew  

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andrew.bridget(at)telus.n
Guest

Posted: Tue Aug 28, 2007 4:59 pm Post subject: Weird 747 shadow

Hi, yes, Nico,I think Steve is likely right; I only  read his post after I responded. Talk about opening my yap before I have all the  info 

  

 Found some other aircraft with ghosted shadows.   No I didn't scan Google Earth ... well I did look at O'Hare to see if  there were any on approach/climbout, and at Vancouver, Toronto, Calgary, and ...  but then I gave up and cheated by looking at http://www.gearthhacks.com/dlcat24/Aircraft-in-flight.htm 

  

 Steve, given this, is it not possible that two  photos are taken and then overlaid to give the 3D effect when one tilts the  earth to a more horizontal plane? (pun unintended) This would explain the  aircraft "moving on". In each of the ghosted shadows the ghost aircraft  appears to be on (or slightly higher) than the clear aircraft.  However, on a slower aircraft (like the helicopter, or aircraft on finals) there  isn't any ghosting.This would add to the theory that the aircraft has moved on -  only fast aircraft appear to be ghosted.

  

 Blessings

 Andrew

 [quote]   ---

steve2(at)sover.net
Guest

Posted: Wed Aug 29, 2007 2:45 am Post subject: Weird 747 shadow

Hi Andrew,

  

 It gets a little complicated......

  

 The 3D effect is used by many companies to create  the terrain model used by so many applications. It could be flight simulators,  or GPS units with ground proximity in them.... What Google is doing is using  that model to 'drape' their imagery over it to give you that 3D  effect.

  

 I'll take a look at those examples when I am back  at a fast modem, but I have another 'possible' explanation for what you are  seeing.

  

 In order for an orthophoto to be scaled properly  the original photo has to stretched and shrunk to fit the terrain. Think of the  left side of a photo as having a mountain, and the right side with a valley. The  two sides of one photo will have different scales...... This effect is further  complicated by the fact that only in the center of the image is the camera  looking directly down, vertically. For most of the image, the subject is at more  and more of an angle off center.

  

 This 'looking off center' is not an insolvable  problem as long as the object is draped onto the terrain model. But any object  that stands proud from the terrain model is going to be put in the wrong  place. The higher something is, and the further off perpendicular from under the  camera, the more horizontal error will be introduced when the object is forced  down to the terrain model.

  

 So tall buildings will appear misplaced. Aircraft  could appear a great distance from where they should have been on the earth  directly beneath them.....

  

 The simple answer is; every image pixel needs a  proper elevation in order to be placed accurately in horizontal.

  

 As for multiple images causing ortho-weirdness, it  does all the time. Things like a baseball field with way too many players and a  bunch of other errors, some of them quite funny......

  

 David Owens, on this list, I'm sure takes quite a  lot of imagery destined for ortho photos also, with their Colemill  500A.....

  

 Steve

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bertberry1(at)aol.com
Guest

Posted: Wed Aug 29, 2007 5:14 am Post subject: Weird 747 shadow

For what its worth, I think it has to do with shutter speed.  Slower shutter speed which allows better detail.  In addition, a lot of these are not sat photos but are aerial photos that are piece milled in.



Bert

Sent via BlackBerry by AT&T



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dowens(at)aerialviewpoint
Guest

Posted: Wed Aug 29, 2007 6:32 am Post subject: Weird 747 shadow

Actually, when you use some of the GEO software  such as Leica Suite, and Imagine, some of the features you can choose to "merge"  the images seamlessly allow you to "feather" the images, which makes the image  progressively trsnsparent to the extent of the image... to appear more  seamless between frames, as well as auto dodging, which will change the actual  gamut of each image to match more or less creating another aspect of "seamless"  as the eye can see...  color and density assuming the images were captured  at or near the same sun angle, weather etc. As for the "ghost" shadow, I think  it was feathered below the image that was overlayed after, like you guys said...  BAWK!

  

  

  

  

 David Owens

Aerial  Viewpoint

N14AV

AC-500A-Colemill

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