On Tue, Mar 25, 2008 at 12:56 PM, Carl Lowenstein <[EMAIL PROTECTED]> wrote:
> On Tue, Mar 25, 2008 at 11:11 AM, Ralph Shumaker <[EMAIL PROTECTED]> > wrote: > > > > Karl Cunningham wrote: > > > On 3/24/2008 3:28 PM, James G. Sack (jim) wrote: > > >> Mark Schoonover wrote: > > >>> On Mon, Mar 24, 2008 at 2:37 PM, James G. Sack (jim) > > >>> <[EMAIL PROTECTED]> > > >>> wrote: > > >>> > > >>>> Tracy R Reed wrote: > > >>>>> Neil Schneider wrote: > > >>>>>> Mark Schoonover wrote: > > >>>>>> Some dude did a war flight - similar to a wardrive > > >>>>>>> - in a small plane over San Diego and logged in the thousands. > That > > >>>>>>> was a > > >>>>>>> few years ago. > > >>>>>> That would be our own Tracy Reed. > > >>>>> Indeed it would! > > >>>>> > > >>>>> I have been considering reprising this experiment. If anyone has > the > > >>>>> equipment and wants to put together a proper scientific > experiment > > >>>>> and > > >>>>> do something unique (triangulate the actual location of the AP, > > >>>>> acquire > > >>>>> useful data about the network involved, etc) I would be willing > to > > >>>>> give > > >>>>> it another go. We could even fly the same path as before and > > >>>>> compare the > > >>>>> data. > > >>>>> > > >>>> I wonder what kind of antenna you would want/need for this? > > >>>> > > >>> I don't know. I've done direction finding work before, but only > from > > >>> a fixed > > >>> location. DFing from a plane would be very challenging to say the > > >>> least... > > >>> Normally you'd use some kind of Adcock array for VHF or UHF, but > not > > >>> sure in > > >>> the microwave bands. > > >>> > > >>> There is some info tho: > > >>> > http://www.scitechpublishing.com/index.asp?PageAction=VIEWPROD&ProdID=158 > > >>> > > >>> > > >> > > >> Wouldn't a ordinary omni with hopefully not too thick (and not too > thin) > > >> a donut pattern do the job, even? Have to have readings from 2 > reception > > >> points, of course (plus altitude). Assuming a flat earth makes it > > >> easier, too. ;-) > > >> > > >> Seems like a lot of things need to be done at once, though: > > >> pick a channel > > >> pick a source > > >> try to quickly maximize the source signal > > >> and record direction and altitude > > >> do fast enough to be able to sample all channels, see strong > signals > > >> > > >> Are there programs to help with this? Hardware? > > > > > > Could have a script that does continuous iwlist scanning. My > > > recollection is that a scan takes a second or two to complete, but I > > > don't know if that varies with number of APs found. Record the MAC > > > address and signal strength for all APs seen during each scan, along > > > with GPS coordinates (NMEA-183 text from serial port of GPS). Fly a > > > parallel search pattern. Then (challenge here) post-process to > > > correlate data and put positions to MAC addresses. > > > > > > When an AP is seen on more than one search leg, you should be able to > > > determine a location based on signal strength in those legs. Where an > > > AP is seen only on one leg, you can't do as well. > > > > > > Could be tested by flying patterns over (or driving by) one's own or > > > other known APs. Could possibly 'normalize' the antenna pattern of > the > > > receiver. > > > > > > This ignores the radiation pattern of AP's antennas, but I dunno what > > > you could do about that in any case. > > > > > > Karl > > > > > > > > > > A single point receiver has no depth perception, like having only one > > eye open. > > > > Having two eyes open increases depth perception and the further apart > > the eyes are, the farther depth can be perceived. > > > > Affixed to the plane, this would mean two receivers at either nose and > > tail, or even better, at either wing tip. I have no idea how this > could > > be done safely. > > You have a scale problem. At wi-fi frequencies, the wavelength is > like 5 inches. Sorry, no I don't. Full wavelength at 2.4 Ghz is 4.92 inches. Quarter wave is 1.23 inches, which is approx 31 millimeters... > > > > > A GPS device would allow instantaneous position information for the > > aircraft itself. That and direction of travel with triangulation would > > allow you to fairly well pinpoint the WAPs on the ground (or > elsewhere). > > > > How did the military triangulate enemy radio signals in WWII? (when > > their equipment was far more primitive than even what the CB home user > > has today) > > The "high frequency" triangulated by ship-mounted HF/DF receivers for > U-boat location was seldom greater than 15 MHz. That's the 20-meter > band in ham radio nomenclature. > > You can read an extensive technical description of WWII vintage HF/DF > by following the references in > <http://en.wikipedia.org/wiki/Huff-Duff>. > > carl > -- > carl lowenstein marine physical lab u.c. san diego > [EMAIL PROTECTED] > > > -- > [email protected] > http://www.kernel-panic.org/cgi-bin/mailman/listinfo/kplug-list > -- Mark Schoonover, CMDBA http://www.linkedin.com/in/markschoonover http://marksitblog.blogspot.com [EMAIL PROTECTED] -- [email protected] http://www.kernel-panic.org/cgi-bin/mailman/listinfo/kplug-list
