[PLUG-TALK] DFW airport on google maps

Keith Lofstrom keithl at kl-ic.com
Thu Apr 13 12:58:37 PDT 2006


>>>>> "Keith" == Keith Lofstrom <keithl at kl-ic.com> writes:

Keith> [...] This suggests that the satellite taking the photos is
Keith> probably moving south-to-north, too, and we are looking at two
Keith> stitched together frames with a join somewhere across terminals
Keith> C and D.  Since the satellite is probably in a low orbit,
Keith> moving about 8Km per second, one can probably compute frame
Keith> rates and such for the camera, if you are better at math than I
Keith> am.

On Wed, Apr 12, 2006 at 09:56:37PM -0700, Russell Senior wrote:
> I could be wrong, but I think the nicer hi-res photos on google are
> aerial photos rather than satellite.  Digital orthoquads or something.
> That's why there isn't universal coverage at that scale, but it's
> limited to urban areas of "enhanced interest".

According to the readme for Google local, they are all satellite images,
from EarthSat (www.earthsat.com) for the 15 meter stuff, and the Digital
Globe Quickbird satellite for the hi-res stuff.  For more info, see:
    http://www.digitalglobe.com/about/quickbird.html

The Quickbird was launched out of Vandenberg in 2001, so it is in a
polar orbit.  It has a 128 Gbit buffer, so it can only capture 57
10 mile by 10 mile area images per orbit (2 foot resolution); or
75 million square kilometers per year.  The Earth is 510 million
square kilometers, so the satellite can only do 15% per year.  Some
customers are buying multispectral images of specific sites (like
their farms), and others (like governments and news organisations)
are buying repeated passes of the same area during some crisis, so
only a fraction of that 15% is available for whole-land-area mapping. 
Given the cost of the satellite, I would guestimate that each image
costs in the $100 to $500 range.  Google is unlikely to pay for all
3.5 million square miles of the US, much less the land area of the
world, at that rate.

Digital Globe is building two more satellites to launch in 2007 and
2008, which will increase cabability more than 10X.  At that point,
it might start making sense to do the whole land surface of the Earth.
There are some remote areas that I would like to see in more detail.

Maps and satellites fascinate me.  Forgive me for running on.

Keith

-- 
Keith Lofstrom          keithl at keithl.com         Voice (503)-520-1993
KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon"
Design Contracting in Bipolar and CMOS - Analog, Digital, and Scan ICs



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