I haven't been following the list for a while, so if this cuts into an
older arguement. I apologize.
At 04:45 PM 4/21/00 -0700, Eric Murray wrote:
>On Fri, Apr 21, 2000 at 04:25:45PM -0600, Pope Golgotha Pierced the Zeroth
wrote:
>> On Fri, 21 Apr 2000, Jim Choate wrote:
>>
...
>You could do that now, on current cop radio setups.
>
>You just need a network of cypherpunks with radio scanners, direction
>finders and GPSs, a way to recognize different cops by their radio
>transmissions, and a way to communicate the cop location vector data
>amongst the cypherpunk participants. Recipients need only do the
>triangulation using the vectors to locate the cops.
>
...
You wouldn't even need more than one person. One radio, properly built
using two receivers and some timing circuitry, could locate a transmitter
in much the same way as you can tell where someone is from his voice. If
the signal comes in a little early on the left, but not early enough for it
to be in a direct line with the two antennas, then you have two possible
locations. One forward, one rear. Add a third antenna and you should be
able to get a 2D location down near perfectly.
Problems with this system, and the one you and someone else mentioned.
Radio silence leaves you blind. If the cops wized up to it, they would
begin relying on personal communications, and general public systems, like
CB's and cellular, (please excuse the spelling), phones.
On anything but an idealized plain, obstructions would reflect and absorb
signals, making accurate mapping near impossible until you developed,
probably from experience, a map of the absorbative/reflective effects of
the landscape. Passive echolocation would be bad enough in a forest, try
using it in a cave or other high echo environment.
For the latter problem, using signals as close to the actual police bands
as possible, you could "calibrate" the system. This would be easiest with
fixed placement receivers, but not impossible with mobile units.
Interestingly enough, bearcat, if I recall correctly, made a little police
band scanner designed specifically to alert you when there was activity in
your area. It was (is?) marketed to people who lived in states that had
outlawed radar detectors.
Good luck,
Sean
