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Optical/Observational Perspective Question

  1. Mar 26, 2009 #1

    NWH

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    So I have a couple of questions. Firstly, apologies if these questions are out of place, I figured this could have equally been asked on a photography board, but it involves light and position and stuff like that, so I thought it would be okay.

    Say for example we have two objects, object A and object B, we also have an observer who's standing in area C, some distance away from the objects. One object is slightly behind and away from the other and from the perspective of the observer in area C, the two edges of each object appear to touch. Would it be accurate to assume, that the alignment of the edges of these objects is only visible when the observer is standing in area C? Could we then, draw the alignment of these two objects in Google Earth with the line generator and predict the line of sight and even cross over the position of area C, where the observer was standing? On top of that, would there be any strange optical effects with cameras that might cause the illusion of standing in area C, even though they're in a different position?

    I hope someone doesn't mind answering these questions, I know they're a little out of place (kind of). I'm just interested to know if you can accurately (to some degree) make predictions of position in Google Earth, based on objects and their estimated alignment around you. Thanks in advance...
     
    Last edited: Mar 26, 2009
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  3. Mar 26, 2009 #2

    Danger

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    Welcome to PF, NWH.
    I don't know much about Google Earth. Parallax, however, is restricted to a particular viewing angle and distance. It can't be faked from somewhere else without photo touch-up or the use of some screwy lenses.
     
  4. Mar 26, 2009 #3

    NWH

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    Thanks for the quick reply! As I thought, I figured it would have been definitive with a human as, well, I see it for my self, but I questioned from a camera's perspective. Interesting to know it can't be faked without touching it up. I know lenses can cause strange effects, like apparent distance and even bending of objects, so it was hard to make that judgement. Any idea if lenses can change apparant position?
     
  5. Mar 26, 2009 #4

    DaveC426913

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    One thing to realize about Google Earth is that the maps are stitched together from separate photos taken at possibly widely different angles. You can find areas where two buildings next to each other are leaning in completely opposite directions - like Escher's staircase! You cannot really count on two things at any distance on a map to be accurately inline.
     
  6. Mar 26, 2009 #5

    NWH

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    It could give a good aproximation though, right? I don't mean pin point perfect, just accurate enough to predict the general line of sight over an acceptably broad area?
     
  7. Mar 26, 2009 #6

    DaveC426913

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    Certainly, yeah. I've cross-referenced a bunch of buildings in a photo that were 40 miles away across the lake.

    Why don't you post your pix and let us analyze the scenario? We eat that stuff up.
     
  8. Mar 26, 2009 #7

    Danger

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    That would depend upon your definitions of both 'general' and 'acceptable'. Since this is a science forum, we tend toward minimal tolerance for error. The context is important. It's a lot different to determine whether someone could witness something from a particular spot, or whether a sniper bullet was fired from a particular spot. Can you give us a bit more info about your purpose?

    edit: Oops! Didn't mean to ignore you, Dave. You sneaked in whilst I was composing.
     
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