Lots - for values of lots including "practically all" - of ships use the AIS (Automatic Identification System), which broadcasts various details on radio. For an example application, try www.aisliverpool.org.uk
On Fri, Apr 11, 2008 at 6:44 AM, <[EMAIL PROTECTED]> wrote: > On Tue, 08 Apr 2008 22:16:57 PDT, Joel Jaeggli said: > > > spot can generally deliver an image within 1 day in 60kmx60km blocks > > assuming no contention for the slot. 20m resolution is more than > > adequate to pick up ships underway at sea. ikonos can deliver 11x11km > > swaths. > > And ikonos can do a lot better than 20m resolution. We had ikonos target > the campus for a special event a few months ago: > > http://glovis.geog.vt.edu/hokiesthanktheworld/ > > "The full extent of the satellite image is approximately 100-square > kilometers, > stretching from Brush Mountain (upper left) across Blacksburg (center) to > Ellett Valley (lower right). The Virginia Tech Drillfield is located near > the > center of this November 17, 2007 scene from the GeoEye IKONOS satellite. > This > true color rendering by Peter Sforza combines red, green, and blue > wavelengths > (3.7-meter pixels) into a RGB color image, and sharpened using the > panchromatic > band (0.92-meter pixels). Note the sun's angle of elevation was 32 degrees > and > the azimuth was 164.1 degrees (north being zero)." > > 1-meter pixels sounds about right - if you look at the right place on the > full-scale image, you can find (and tell the difference between) my dark > green > Camry, and the immediately adjacent dark grey Nissan my neighbor drives, > and > still see 3 feet worth of parking lot pavement in between them too... > > Not bad for 423 miles up and moving at 4.7 miles per second.... > > >
