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warwalker · 08-24-2004

I've been playing around with this idea myself (and REALLY appreciate the additional resources you've referenced), and have come to the following conclusions:

1- The biggest impediment to the quasi-triangulation you refer to is the inconsistent nature of the typical urban landscape. whether you and the AP are separated by a window or steel re-inforced wall seems to affect the signal you receive much more than your distance from it, so a snapshot of the rssi at one point might give the impression that you've moved away from the AP when you've actually moved closer but into a wifi "shadow". Also, reflective surfaces -- such as neighboring buildings -- can bounce signals in decpetive ways.

2- A very practical and accessible solution is a well-shielded yagi, which, when used in conjunction with an app with a good and responsive graphical representation like PocketWinC or PocketWarrior, can help pinpoint the exact office from which a signal is emanating -- even at (relatively) great distance.

3- A more elegant solution might be one simultaneously using two or more receivers. I do all my work on foot and via PDA (IPAQ 2215, Ambicom GPS-CF and SanDisk-SD). I'm interested to know whether two separate, well-calibrated PDAs working simultaneously with identical gross spatial orientation relative to the AP, but separated by 3-5 feet, could detect a meaningful signal differential without being overly thwarted by the signal nuances I describe above. I think that an examination of the log, eliminating signal outliers and accounting for inevitable hardware differences and error, could yield some good data.

Just my impressions. Of course, I'm new to this, so maybe it's been done.

Warwalker

08-24-2004	#3 (permalink)
warwalker Registered Member Join Date: May 2004 Posts: 8	I've been playing around with this idea myself (and REALLY appreciate the additional resources you've referenced), and have come to the following conclusions: 1- The biggest impediment to the quasi-triangulation you refer to is the inconsistent nature of the typical urban landscape. whether you and the AP are separated by a window or steel re-inforced wall seems to affect the signal you receive much more than your distance from it, so a snapshot of the rssi at one point might give the impression that you've moved away from the AP when you've actually moved closer but into a wifi "shadow". Also, reflective surfaces -- such as neighboring buildings -- can bounce signals in decpetive ways. 2- A very practical and accessible solution is a well-shielded yagi, which, when used in conjunction with an app with a good and responsive graphical representation like PocketWinC or PocketWarrior, can help pinpoint the exact office from which a signal is emanating -- even at (relatively) great distance. 3- A more elegant solution might be one simultaneously using two or more receivers. I do all my work on foot and via PDA (IPAQ 2215, Ambicom GPS-CF and SanDisk-SD). I'm interested to know whether two separate, well-calibrated PDAs working simultaneously with identical gross spatial orientation relative to the AP, but separated by 3-5 feet, could detect a meaningful signal differential without being overly thwarted by the signal nuances I describe above. I think that an examination of the log, eliminating signal outliers and accounting for inevitable hardware differences and error, could yield some good data. Just my impressions. Of course, I'm new to this, so maybe it's been done. Warwalker Last edited by warwalker : 08-25-2004 at 07:23 AM.