Scott in Aztlan ) writes:
On Sun, 14 Sep 2003 05:14:48 GMT, "Craig Davidson" wrote:

What frequency?

2.4GHz. :)

Sounds like a microwave oven. :-)

Or a cordless phone... Or an X-10 wireless camera... :) :)

Or an 802.11B wireless access point?

Hmm... Come to think of it, that might be a possibility, too! ;)

Lots of people make WiFi maps by "wardriving:" driving/walking/biking/training
around with a laptop and a program like Network Stumbler
(http://www.netstumbler.com) and a GPS receiver. A typical map looks like this:

http://www.wificharlottetown.org/loc...ttetownmap.jpg

But in this case, you only need to find places where there is enough signal
strength for access, not find the exact point of the access transmitter.

If you can get access at XXX corner, it doesn't matter if the access
transmitter is right next to you, or down the block.

Michael VE2BVW

Scott in Aztlan ) writes:
On Sun, 14 Sep 2003 05:14:48 GMT, "Craig Davidson" wrote:

What frequency?

2.4GHz. :)

Sounds like a microwave oven. :-)

Or a cordless phone... Or an X-10 wireless camera... :) :)

Or an 802.11B wireless access point?

Hmm... Come to think of it, that might be a possibility, too! ;)

Lots of people make WiFi maps by "wardriving:" driving/walking/biking/training
around with a laptop and a program like Network Stumbler
(http://www.netstumbler.com) and a GPS receiver. A typical map looks like this:

http://www.wificharlottetown.org/loc...ttetownmap.jpg

But in this case, you only need to find places where there is enough signal
strength for access, not find the exact point of the access transmitter.

If you can get access at XXX corner, it doesn't matter if the access
transmitter is right next to you, or down the block.

Michael VE2BVW

Scott in Aztlan wrote in message ...
On Sun, 14 Sep 2003 05:14:48 GMT, "Craig Davidson"
wrote:

What frequency?

2.4GHz. :)

Sounds like a microwave oven. :-)

Or a cordless phone... Or an X-10 wireless camera... :) :)

Or an 802.11B wireless access point?

Hmm... Come to think of it, that might be a possibility, too! ;)

Lots of people make WiFi maps by "wardriving:"
driving/walking/biking/training
around with a laptop and a program like Network Stumbler
(http://www.netstumbler.com) and a GPS receiver. A typical map looks like
this:

http://www.wificharlottetown.org/loc...charlottetownm
ap.jpg


Scott, i recommend you write software to collect the lat/lon of only the
maximum signal strength readings. then average all the latitudes (add all
the latitudes up and then divide by the number of samples). This should
result in an "average latitude" line on a map. then do the same for all the
longitudes. This "average" result should give you the location of the
transmitter if you take enough samples.

If you want to get clever then take lat/lon samples of many signal strength
readings but keep them separate. Only perform the averaging process
described above on lat/lons that had the same signal strength reading. All
of these "averages" should cluster around the transmitter location in
lat/lon. There is no need to convert lat/lon to anything else. keep it
simple. If you want to get even better results then the last step would be
to average the results of all the averages of all the signal strength
readings to pick one single most likely spot for the transmitter.

If the signals can be identified by a node name or an IP address then by all
means keep the samples sorted by access point id as you perform the
averages. if every access point is using the same default id then the job
will be a little harder.

This almost sounds like more fun than Geocaching

Scott in Aztlan wrote in message ...
On Sun, 14 Sep 2003 05:14:48 GMT, "Craig Davidson"
wrote:

What frequency?

2.4GHz. :)

Sounds like a microwave oven. :-)

Or a cordless phone... Or an X-10 wireless camera... :) :)

Or an 802.11B wireless access point?

Hmm... Come to think of it, that might be a possibility, too! ;)

Lots of people make WiFi maps by "wardriving:"
driving/walking/biking/training
around with a laptop and a program like Network Stumbler
(http://www.netstumbler.com) and a GPS receiver. A typical map looks like
this:

http://www.wificharlottetown.org/loc...charlottetownm
ap.jpg


Scott, i recommend you write software to collect the lat/lon of only the
maximum signal strength readings. then average all the latitudes (add all
the latitudes up and then divide by the number of samples). This should
result in an "average latitude" line on a map. then do the same for all the
longitudes. This "average" result should give you the location of the
transmitter if you take enough samples.

If you want to get clever then take lat/lon samples of many signal strength
readings but keep them separate. Only perform the averaging process
described above on lat/lons that had the same signal strength reading. All
of these "averages" should cluster around the transmitter location in
lat/lon. There is no need to convert lat/lon to anything else. keep it
simple. If you want to get even better results then the last step would be
to average the results of all the averages of all the signal strength
readings to pick one single most likely spot for the transmitter.

If the signals can be identified by a node name or an IP address then by all
means keep the samples sorted by access point id as you perform the
averages. if every access point is using the same default id then the job
will be a little harder.

This almost sounds like more fun than Geocaching

Scott in Aztlan writes:

Since my WiFi card is built into my laptop, to use a directional antenna will
require disabling the internal WiFi card, buying a new PCMCIA card with an
external antenna jack, and buying a directional antenna - expenses I'd hoped to
avoid, but which now appear necessary.

If you want to try this with the internal antenna, you should be aware
that it is probably *far* from omnidirectional. Even if the antenna
design itself is something that would have an omnidirectional pattern in
the middle of an open field, the proximity of other metal within the
laptop itself will mean that the pattern "in situ" is far from
omnidirectional. You can see this to some extent by just rotating the
laptop while sitting in one place and watching the RSSI change.

Then when you put that laptop inside a car, the car will further modify
the reception pattern.

Dave

Scott in Aztlan writes:

Since my WiFi card is built into my laptop, to use a directional antenna will
require disabling the internal WiFi card, buying a new PCMCIA card with an
external antenna jack, and buying a directional antenna - expenses I'd hoped to
avoid, but which now appear necessary.

If you want to try this with the internal antenna, you should be aware
that it is probably *far* from omnidirectional. Even if the antenna
design itself is something that would have an omnidirectional pattern in
the middle of an open field, the proximity of other metal within the
laptop itself will mean that the pattern "in situ" is far from
omnidirectional. You can see this to some extent by just rotating the
laptop while sitting in one place and watching the RSSI change.

Then when you put that laptop inside a car, the car will further modify
the reception pattern.

Dave

Since my WiFi card is built into my laptop, to use a directional antenna will
require disabling the internal WiFi card, buying a new PCMCIA card with an
external antenna jack, and buying a directional antenna - expenses I'd hoped to
avoid, but which now appear necessary.


Back to Best Buy.


Friends don't let friends shop at Best Buy.


You need to check the weekly sales at Best Buy, Circuit City, Staples &
Office Depot to get the best deals. Everything I want goes on sale at
some point, I just have to wait a few weeks. I don't pay full retail.

Since my WiFi card is built into my laptop, to use a directional antenna will
require disabling the internal WiFi card, buying a new PCMCIA card with an
external antenna jack, and buying a directional antenna - expenses I'd hoped to
avoid, but which now appear necessary.


Back to Best Buy.


Friends don't let friends shop at Best Buy.


You need to check the weekly sales at Best Buy, Circuit City, Staples &
Office Depot to get the best deals. Everything I want goes on sale at
some point, I just have to wait a few weeks. I don't pay full retail.