[UFO Chicago] Google Maps vs Terraserver

[Neil R. Ormos]

On Fri, 14 Oct 2005, Jordan Bettis wrote:

> Google appears to get most of its aerial survey data from
> <http://digitalglobe.com>. According to this:
> <http://en.wikipedia.org/wiki/Google_earth> the data is "usually less than
> three years old." This confirms that terraserver gets its data from USGS:
> <http://en.wikipedia.org/wiki/TerraServer-USA>. Interestingly it used to
> have Russian data as well.

I don't think that anyone was saying that the
satellite image data distributed by Google and the
map data distributed by Terraserver arrive at each
distributor via identical routes or are perfectly
coextensive.

What I did say was that the satellite image data
distributed by Google is derived from the same
USGS imagery that Terraserver delivers via the
"Urban Areas" tab, at least for the Chicago area,
and that the Google-provided imagery seems to have
been stripped of some color depth.  TerraServer
itself credits USGS as the source of its imagery.

Here's an example, using our meeting location.
Note the identical pattern of vehicles on Irving
Park Rd. in each image (particularly the red,
white, and blue cars at the intersection of Tripp
and Irving Park).  It's highly unlikely that the
Google and Terraserver imagery (at least for the
Chicago area) are derived from different primary
sources (i.e., sources that originally acquired
the data using different satellites or aerial
surveys or on different dates).

Google (click the SAT button):

  <http://maps.google.com/maps?sc=1&hl=en&output=html&q=4229+W+Irving+Park+Rd%2C+chicago%2C+il&btnG=Search>

Terraserver:
  <http://terraserver.microsoft.com/image.aspx?t=4&s=8&Lon=-87.73360913&Lat=41.95357296&Alon=-87.73360913&Alat=41.95357296&w=1&opt=0&addr=4229+W+Irving+Park+Rd%2c+Chicago%2c+IL+60641&qs=4229+w+irving+park+rd%7cchicago%7cil%7c>

--Neil