GPS bread crumb& Signal % help

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GISGUY
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GPS bread crumb& Signal % help

Post by GISGUY » Mon Dec 28, 2009 8:46 pm

Hello... I'm a GIS grad student looking for a way to have a GPS bread crumb (ie a series of waypoints) that is appended with AP information. Specifically signal strength.

Right now it seems that the signal strength is not logged per waypoint. But rather its averaged per AP and attached to a waypoint. I would like to have day 10,15,20... waypoints for a single AP. Then generate a detailed map based on those waypoint values.

I'm running vista so netstumbler won't work for me... Any suggestions?

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Re: GPS bread crumb& Signal % help

Post by ACalcutt » Mon Dec 28, 2009 9:03 pm

The closest thing i have with vistumbler is the export to KML. Export to KML has the option of mapping signal strength (http://forum.techidiots.net/forum/viewt ... f=33&t=278)

The vistumbler VS1 file also keeps all the information you are looking for, but AP data would need to be matched up with GPS data (the VS1 format information is here: http://sourceforge.net/apps/mediawiki/v ... VS1_Format)

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Re: GPS bread crumb& Signal % help

Post by ACalcutt » Tue Dec 29, 2009 3:28 am

there is also the option of Text NS1. Even though scanning does not work with netstumbler, you can import a Text NS1 from vistumbler, and use whatever methods worked with netstumbler

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Re: GPS bread crumb& Signal % help

Post by GISGUY » Mon Jan 11, 2010 6:57 pm

Hey great info Andrew.
Thanks for getting back to me.

Sorry for the delay I was expecting an email notice of a reply. so I hadn't checked back here in awhile.

So have a lot of questions hope you don't mind?

Wifi isn't my forte so please forgive my lack of background knowledge.

I've got a few of options now. Here is what I have.

1. I can use a old xp laptop with a new EnGenius external USB wifi adapter. But come find out it works but its not supported by NetStumbler so I guess it won't / might not give me true SNR values.

Special note: I don't really know what SNR values are but I would like something that is relativity accurate. I didn't know NetStumber was configured to work with special hardware.
The idea is I would use the signal range to map the APs but NetStumber uses SNR. My Netstumber setup gives me [ SNR Sig Noise ] something like this:

[ 40 89 49 ]
[ 7 56 49 ]
[ 40 89 49 ]
[ 7 56 49 ]
[ 7 56 49 ]
[ 40 89 49 ]
[ 7 56 49 ]
[ 40 89 49 ]
[ 40 89 49 ]
[ 7 56 49 ]


Notice how all the last values are always 49... I question that these would always be the same as they are here.
Below isn't from the dataset above but When I export NS1 from VistaStumberI and open it in NetStumber the resulting [ SNR Sig Noise ] data looks similar in format except the last value is always 50...

[ 70 120 50 ]
[ 70 120 50 ]
[ 76 126 50 ]
[ 76 126 50 ]
[ 60 110 50 ]
[ 60 110 50 ]
[ 60 110 50 ]
[ 66 116 50 ]
[ 66 116 50 ]

So I'm not sure what numbers to use and which would be most appropriate using the netstumber export.

I did a test run using the xp/EnGenius NetStumbler data and it worked somewhat... or at least a got a map. However if my Wifi adapter isn't officaly supported I'm wondering if I really had something legitimate or if it was erroneous because of the hardware wasn't supported.

2. I can use VistaStumber using the VS1 file extension and reformat it in excel. I have some question on how to do that exactly, especially if I have several APs. It seems that it would be easier to export to NS1 and use netstumber to format it.
The other question is about the SNR... I'm not sure if its important in my case or how to use those values. VistaStumber seems to use signal history how does that relate to SNR? Will signal history be more accurate or different for me compared to Netstumber in my situation when using non supported hardware?

3. I can export from VistaStumbler the NS1 to NetStumber and then export out the data. But as noted above I get values that I'm just sure how to use or are correct.
Does NetStumble somehow convert the VistaStumbler NS1file for its own use?

Thanks again Andrew...
My apologies for the long post

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Re: GPS bread crumb& Signal % help

Post by ACalcutt » Mon Jan 11, 2010 7:22 pm

The main issue with exporting to NS1 is that Vistumbler does not have a source of SNR, Noise, or dbi signal values. Netsh, which is what vistumbler uses to get wifi data, gives signal strength in a percentage value.

This means, to export to NS1 I basically had to make my own SNR values. The export to NS1 was made a long time ago, and could probably use some work, but basically this is what vistumbler outputs.

[ SNR Sig Noise ]
[ " & $Signal & " " & $Signal + 50 & " 50 ]"
so if signal is 25 it would display
[ 25 75 50 ]"

which was based on a netstumbler forum post that stated "Signal - Noise = SNR". Since i do not have a noise value, 50 was assumed.

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Re: GPS bread crumb& Signal % help

Post by ACalcutt » Mon Jan 11, 2010 7:28 pm

On another note. If there's anything I could do to make vistumbler easier to use, please let me know. I could add a more detailed output that could be put into a spreadsheet easier.

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Re: GPS bread crumb& Signal % help

Post by ACalcutt » Mon Jan 11, 2010 11:38 pm

I put out a beta update tonight (v9.81 Beta 1) with a few improvements. (its only available though auto-update or svn right now)

One thing i added is a detailed csv export which has all AP data and GPS data in a nice csv format.

Detailed CSV exports the following data with full history
SSID,BSSID,MANUFACTURER,SIGNAL,AUTHENTICATION,ENCRYPTION,RADIO TYPE,CHANNEL,BTX,OTX,NETWORK TYPE,LABEL,LATITUDE,LONGITUDE,SATELLITES,HDOP,ALTITUDE,HEIGHT OF GEOID,SPEED(km/h),SPEED(MPH),TRACK ANGLE,DATE(UTC),TIME(UTC)

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Re: GPS bread crumb& Signal % help

Post by GISGUY » Tue Jan 12, 2010 2:39 am

Hi Andrew
I've installed the vs.

The detailed spread sheet looks really good... Having the detailed spread sheet is much easier to work with and to customize. The new spreadsheet format is much better than what NetStumbler is exporting. My thanks for that!


I'm trying to understand SNR and why it is used or why it important. First off in your opinion is the SNR an important value to have/know? How does it compare to the Signal Value of Vistumbler?

With Vistumbler and NetStumblerthe Signal values are currently represented in tens. In Vistumbler Is it possible represent the Signal values in tenths or even hundredths?

During my tests while in motion the NS Signal don't seem to change much. This makes the resulting map jagged / jumpy. For example I would move 50 feet and have a value remain constant. It would be useful if the value had a little more resolution to it if possible.

What are your thoughts?

Again thanks helping me understand this material.

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Re: GPS bread crumb& Signal % help

Post by ACalcutt » Tue Jan 12, 2010 10:14 am

Vistumbler represents signal as a percentage 0% - 100% which is pulled from the netsh output. I imagine, but don't know for sure that this value is derived from some combination of signal and noise. Basically the percent value represents quality of the signal in percent. There is not really much i can do to change this.

Netstumbler (from what i understand) works at a higher level with the hardware to read direct dbi Signal and Noise values. These Signal and Noise values are used to make the SNR value, which also represents quality of the signal (but in dbi). From what i've seen, usually netstumbler ranges from -80dbi to - 30dbi


over at the INSSIDER forums I read that there is no real standard for how a wireless card is supposed to show signal, so output may differ greatly between different brands of network card.

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