I hope my posts aren't coming across as personally directed at you. My intention was to point out that the author greatly exaggerated those satellite systems capabilities.

As for my experience, I was an Air Force officer who worked on space systems for 7 years. After getting out of the Air Force in 1992, I also did work on the Milstar and UFO (UHF Follow On) programs. While in the Air Force, I got to see some actual spy satellite images and worked as a Squadron Intel Officer. Those images were very impressive but not good enough to do things like read license plates.

Yes, the actual resolution of these systems is highly classified. Some researchers have published figures (like that 3 cm number) based on what is theoritically possible for optics looking through the atmosphere. There are other issues, such as available bandwidth, that play into how high the resolution can be for a given system. There is another factor - the higher the resolution, the narrower the field of view tends to be. Super high resolution really isn't needed for most intelligence analysis. It's often better to accept a lower resolution to get a wider field of view, such as looking at all of the ships in a harbor instead of one particular ship.

The civilian Ikronos satellite has a 1 meter resolution, enough to tell if your car is in your driveway but not enough to take your picture (unless you're pretty wide). As an example, here's an Ikonos image of the Pentagon that was taken last September 12th. Still, those images are good enough to provide a lot of intelligence data. That's why the military purchased all of Ikronos's images of the Afghanistan area following 911. Some of these images have since been released, as seen here.

It was also important to deny that info to the other side so they can't see what we're doing. During the Gulf War, all SPOT images of the region were embargoed to Iraq so he couldn't know what we were up to. Had he had those images (and they were about 3 meters resolution), we couldn't have pulled off Swartzkoff's famous "Hail Mary" maneuver to flank Saddam's forces.

Movies like "Enemy of the State" protray the fiction that the government can instantly call up a spy satellite at any time and do things like track a specific car in traffic. The movie is highly bogus for several reasons. First, those satellites are in low Earth orbits, so they can't hang around over any particular area. On the contrary, those satellites only pass over a given location for a few minutes at a time and not even on every orbit. To do what they portrayed in the movie, you'd need hundreds of those satellites up there. Then, you'd have to give the satellites coordinates accurate enough to point at the specific car along with further coordinates to track the car as it moved. Visualize pointing a telescope moving over 17,000 MPH at a moving target on the ground and you'll see just how difficult such a proposition is.

Having worked on satellite systems, I learned a lot about orbital mechanics. LEO satellites are in defined orbits that can only be changed by firing their thrusters. However, this is something that is never taken lightly. The lifetime of LEO satellites is limited in part by the amount of fuel they can carry. Atmospheric drag is enough to cause a LEO satellite to burn in unless it periodically fires thrusters to reboost. The higher the orbit, the lower the drag so you don't have to burn propellant as often. However, the higher the orbit, the bigger the optics need to be to achieve a given resolution.

ELINT stands for Electronic Intelligence. Basically, that covers intercepting radio emissions and analyzing them to determine what the other side is up to. For example, some ELINT system record radar system signals to determine things like Pulse Repetition Rate, operational frequencies, possible sensitivity, etc. This info is highly useful for developing tactics and countermeasures. Other ELINT systems are designed to do things like locate enemy ships at sea or to listen in on communications to keep up with the other side's activities, intentions, and order of battle (stuff like their force composition and chain of command).

If you go here, you can see some Ikonos images that were released in 1999. The one of the Eiffel Tower is very cool. The one of the Air Force Academy is good, too. It just missed showing my house by a mile or two.