On 26/04/2009 17:29, Jeff Liebermann wrote:
> On Sun, 26 Apr 2009 11:34:17 +0100, LR<lrme@privacy.net> wrote:
>
>>> I also created similarly useless results with multiple AP's at my
>>> house. If I walked in a circle, the results were similar to the
>>> photo. However, if I followed the instructions, and sorta walked in a
>>> semi-drunken manner, with lots of cross-over points, the plots looked
>>> more like in the examples.
>
>> Is this because you never get close enough to the AP's to get some
>> positions with really strong signal levels for each AP?
>
> Dunno. I would have to see the raw collected data to determine what's
> happening. Also, I would need some clue as to the algorithm used. In
> the outdoor case, my guess(tm) is that the huge variations in signal
> strength are rendering the data useless. There may also be a problem
> with the large number of SSID's collected. In the indoor case, it
> seems to be a problem with the algorithm used, or possibly because the
> room is small enough that I might get equal signal strength almost
> anywhere in the room. If it does something really crude, like average
> or peak detect the indicated signal strength of ALL the AP's heard,
> that might explain the almost uniform signal level indicated. It may
> also be that my wireless devices are returning garbage values. That's
> dubious as I tried 3 different laptops, but still possible. Lots of
> possibilities, but nothing definitive, yet.
>
> Unfortunately, the software does not offer any means to filter the
> results, limit the test to a specific set of SSID's, or lock it on a
> specific channel. It's difficult to tell what's happening without
> filters. The full version called "Ekahau Site Survey" does these and
> much more.
> <http://www.ekahau.com/products/ekahau-site-survey/overview.html>
> The problem is that it costs $2,200 and $2,700 for the pro version.
> Ouch.
>
> I'll play with it some more later and see if I can deduce how it
> works.
>
I wondered if it recorded the peak value of each AP at each location but
needed a high signal level, say -50dBm, for at least one AP to provide
some form of reference. Looking at your survey I would say you probably
did your first check outside your home/office and recorded a low signal.
Have you tried doing your first check inside your office where there is
a high signal level and then going outside for the next check?