Calling Willem and other bush trackers
Submitted: Sunday, Mar 01, 2009 at 21:47
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Member - Mal and Di (SA)
A South African friend showed me an interesting thing on Google Earth today.
Go to S 26 30 36.77 and E 20 35 35.59 and tell me what animal made these tracks.
It shows what is available on this site but they do not let us have access to.
Scary!
M.
Reply By: Member - Chris & Sue (QLD) - Monday, Mar 02, 2009 at 15:29
Monday, Mar 02, 2009 at 15:29
G'day Mal,
Conspiracy theories to the contrary, I don't think this is from a satellite. It (and the link provided by 'age' of the Arabs in
the desert) are aerial photos. In the Arab shot, most of them are looking at the camera. You don't generally stand around at a
waterhole looking up at a satellite in the daytime (
well, I don't, anyway). :-)
Yes, the owners of the satellites get to see more than your average Fred Dagg does on Google Earth, but I'll think you'll find there are physical limitations to the optical resolution of space based cameras.
As a rough example, a 4m diameter telescope at about 100km altitude (and I suspect their higher than that but we're keeping this simple) has a resolution, under perfect atmospheric conditions, of about 10cms. The resolution of those locations on GE are way below that.
The question in my mind is "Why those 2 locations, both in the middle of nowhere"?
Cheers,
Chris
AnswerID:
351863
Follow Up By: Member - Chris & Sue (QLD) - Monday, Mar 02, 2009 at 15:33
Monday, Mar 02, 2009 at 15:33
The 'rough example' paragraph should have read:-
As a rough example, a 4m diameter telescope at about 100km altitude (and I suspect they're higher than that but we're keeping this simple) has a resolution, under perfect atmospheric conditions, of about 10cms. The resolution of those locations on GE are way below that. For the terminally nerdish, the angular resolution for a telescope (which is what a spy satellite is, essentially something like the Hubble Space Telescope pointed down) is approximated by:
R = ?/D
where R is the angular resolution in radians, ? is the wavelength of light that is being imaged, and D is the diameter of the telescope.
(Parts pinched from
Optical Equation)
Cheers,
Chris
FollowupID:
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Follow Up By: Member - Willie , Sydney. - Monday, Mar 02, 2009 at 22:47
Monday, Mar 02, 2009 at 22:47
Yes Chris, that was the first thing that I thought . Why this incredible resolution on a tiny patch of desert. Maybe they were just testing a camera or some other piece of equipment.
Mal and Di (SA) - thanks for the post - very interesting.
Willie.
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