Planet Four Talk

map projected

  • eagiles by eagiles

    i have asked a few times about the position of the sun, not bothered about lower right or upper left, what i do not understand is the expression "map project" i do have some ideas as to what this means, but to fully understand something it is no good being like plato's cave prisoners.

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  • michaelaye by michaelaye scientist

    when a satellite orbits a body, its distance to the surface is not constant, due to the orbit being sligthly elliptical. This means that, e.g. a 100 pixel wide CCD line sees 100 m at one point of time, but 120 at the next, because it's taken from higher above. Map-projecting an image means correcting for these changes, so that the scale is everywhere the same in the image.

    HTH?

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  • michaelaye by michaelaye scientist

    I don't understand though what you mean when first you ask for the position of the sun, and if somebody tells you, it's from the lower right, then you are not bothered about it? Don't get that...

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  • eagiles by eagiles

    i have as such mastered the ability to see crevasses when they are crevasses, but sometimes there is just something that does not tally a dark spot that looks like a shadow, i thought the images did not always have the sun from the same position, hence the query and some times there is so little contrast or a point of reference to tell whether it is a mound or dip and the query is to confirm which ,

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  • eagiles by eagiles in response to michaelaye's comment.

    sorry i get the answer that the image is not map projected is what i didn't understand, the sun i do understand and it answers the problem i was having with a lump or dip, now i understand map projected because of your explanation thank you

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  • AUricle by AUricle in response to eagiles's comment.

    i have as such mastered the ability to see crevasses when they are crevasses

    Ed, would you mind sharing how exactly you did that?...(I'm assuming you're not flipping the image or making a 'negative' of the original).

    I still have a devil of a time!

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  • eagiles by eagiles in response to AUricle's comment.

    I screw up my eyes so that only a fuzzy image is visible, focusing slowly on a dark image and remembering that it should be a crevasses, it seems to work but not always the first time and with the very red and whiteit is almost impossible

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  • AUricle by AUricle in response to eagiles's comment.

    I screw up my eyes so that only a fuzzy image is visible...

    Ahhh.....funny! I've tried that, squinting, looking at it cross-eyed. Sometimes it works, and sometimes only for a few seconds, or some switch back and forth at will....but not at my will! 😉

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  • eagiles by eagiles

    oh it can change back easier than it stays, unfortunately it could also be frame of mind, colours and an odd shadow that just does not figure, i can not do it at will and sometimes it is a headache, but others are easy, there is in some an edge that if you focus on or refocus from squinting at it it then jump out, don't think going cross-eyed will help, you know when you pretend to be asleep and watch through your eyelashes that what i mean, i had a thought about dark glasses but that did not work.

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