What GPS hardware should I get?

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primal
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What GPS hardware should I get?

Post by primal » Thu May 21, 2009 7:06 pm

First of all, to all of those involved, thank you for making vistumbler! I am happy to report that vistumbler was extremely easy to set up and worked effortlessly. i have a hp dv5t with a realtek wireless adapter. My question however is regarding GPS hardware. I appologize if this is posted somewhere else but I couldn't find a clear answer to this. What GPS hardware is compatible with vistumbler? I preferably am looking for something as that works out of the box just like vistumbler worked perfectly with my wireless card, but I am willing to do some extra setup if it improves some sort of functionality.

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Re: What GPS hardware should I get?

Post by ACalcutt » Fri May 22, 2009 7:04 am

I have only used 3 gps devices myself. These are all compatible

Microsoft GPS-500 (pharos) - this is what i am using now
Microsoft GPS-360
Progin SGM-108 (cheap ebay gps)

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Re: What GPS hardware should I get?

Post by primal » Fri May 22, 2009 3:01 pm

Thanks for the response. Which one of those is the best and why? Does it make a difference or should I just go for the cheapest?

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Re: What GPS hardware should I get?

Post by ACalcutt » Fri May 22, 2009 5:51 pm

Mainly for me it was about availability. The microsoft GPS was available at most stores and was usually very close in price to the others and also came with a up to date version of streets and trips. The two microsoft GPSs were bought as quick replacements, so I never really price checked online ;-).

I have liked the gps-500 the best so far, It is more accurate than the gps-360 and gets a gps fix faster. The gps-360 is bigger, but worked well. The progin one had a magnet on it...which was helpful...but this one didn't last long and wasn't as compatible(OS wise)

The only advice I have if you get the GPS 360 or 500 is be careful of the cable connector that plugs into the gps.....I have ruined 2 of these cables ends and they aren't easy to get without buying another gps(unless that has changed from the last time :-) )

Picture from somewhere...Gps-500(w/new connector) on the left and Gps-360 on the right
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Re: What GPS hardware should I get?

Post by mysticvirgo67 » Sun Jun 28, 2009 5:01 pm

I have same GPS gear.. for $50 with software.. can't beat it. Would be nice if 'stumbler worked with MS Streets and trips software, though
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Re: What GPS hardware should I get?

Post by ACalcutt » Mon Jun 29, 2009 12:57 am

mysticvirgo67 wrote:Would be nice if 'stumbler worked with MS Streets and trips software, though
Trust me, i've looked into the streets and trips format and would love to support it. I just find very little information on the format and haven't yet figured out how to make a s&t file. If only MS would support a standard format...like GPX or something ;-).

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Re: What GPS hardware should I get?

Post by mysticvirgo67 » Mon Jun 29, 2009 11:17 am

Well.. my other hobby is Geocaching and there is a peice of code called GSAK that does that conversion from LOC and GPX http://www.gsak.net/ Umm.. If you could provide Vistumbler with a CSV text format, MSST will import from those. Won't be realtime, but will be a start?
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Re: What GPS hardware should I get?

Post by kvg » Fri Apr 16, 2010 5:49 pm

Some one Please suggest can I use TOM TOM GPS for war chalking?

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Re: What GPS hardware should I get?

Post by ACalcutt » Fri Apr 16, 2010 6:21 pm

I don't think so. you need a NMEA compatible GPS like the ones above. From what I see it does not look like the tom tom outputs nmea data over serial or usb cable.

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Re: What GPS hardware should I get?

Post by TT13E » Thu Feb 16, 2012 4:48 pm

I've got a TomTom.
I merge nmea data log files with Vistumbler files at journey's end.
The results aren't bad !

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Re: What GPS hardware should I get?

Post by ChuckE » Thu Jan 16, 2014 12:59 pm

I'm new at this and am still trying to figure out what to do with this but I think I've had success using a Magellan Triton GPSr with Vistumbler . I found that if I connect to my Dell laptop with the USB serial cable and the GPS set to NMEA-USB I get readings on the chart. I'm trying to do it again (it worked last night) but it's not working so I opened last night's saved session. I have the GPS unit set to NMEA-USB NMEA Option V2.1 GSA Baud Rate 4800,8,N,1.
GPStumb.JPG
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I'm not quite sure how this is happening but my list of detected APs shows on Google Earth with my approximate location in a plot along with all of those detected. It isn't really precise as the screenshot shows a balloon where I am but that's not my network. If it's visible on the attachment, the point that's red is the one that brings up a balloon with my AP details. As I'm doing this I can't picture at this time driving around with it yet. Last night as I was trying this out Google Earth (or Vistumbler) had one point flashing that was labeled "Current Location" and I had trouble keeping zoomed in. Everytime I stopped zooming the screen would zoom back out.

What I'm really wondering though is how is the location of these other APs on my list calculated? When I get used to this do I just drive around and Vistumbler keeps a log of all of the APs that I pass and their approximate locations?

Like I said, I'm new at this and if anyone can point me to other posts that would help me understand this a bit better please do. I guess I did sort of answer the question as to one GPS that seems to work.
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Re: What GPS hardware should I get?

Post by ChuckE » Thu Jan 16, 2014 1:00 pm

I really have to start looking at the dates on forums that I join to see how old they are! :oops:
I don't get lost. Where I'm going gets lost.....

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Re: What GPS hardware should I get?

Post by ChuckE » Fri Jan 17, 2014 10:47 am

wOw I ended up having to go for a drive yesterday and put the laptop in the back seat with the Triton hooked up to it and found 608 APs on the trip and 519 on the return trip with a different route. Amazing program. :D
I don't get lost. Where I'm going gets lost.....

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What GPS hardware should I get?

Post by arizonajon » Thu Feb 05, 2015 10:54 am

Hi ChuckE -

I just joined the forum yesterday hoping that anyone was left. I'm having an issue getting my GPS stream to be read reliably by Vistumbler.

To answer your question "What I'm really wondering though is how is the location of these other APs on my list calculated? When I get used to this do I just drive around and Vistumbler keeps a log of all of the APs that I pass and their approximate locations?"

Unless you're a madman :D , you won't ever drive to the exact location of the A/P, as it's generally inside someone's home or business. But, the signal from that A/P radiates all over the place, and as your setup gets close enough to first hear the signal and record the SSID, it also records your current lat/lon and the A/P's current received signal strength indication (RSSI). If you keep moving around and the RSSI for that A/P becomes stronger than the previous measurement, then VStumb replaces the previous lat/lon with the new position. In theory, if the a/p were outdoor, hanging on a light pole (like they have here) you could literally drive right up to it and perhaps get almost nearly the exact position.

Hope that helps.

Cheers - Jon

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What GPS hardware should I get?

Post by arizonajon » Thu Feb 05, 2015 12:19 pm

More information on my GPS read issue:

Underneath the lines Active APs: and Actual loop time: is a field which, when the Use GPS button has been clicked, shows either the GPS sentences or the message "Seconds Since GPS Update: GPGGA: n/30 - GPRMC: m/30" where n and m are integers.

I see in this field regular GPRMC messages but the counter m in the "Seconds since..." does not return to zero. Less often, I see GPGGA sentences but even when I see them the GPGGA n counter does not return to zero.

After n reaches 30, the Latitude: and Longitude fields reset to N 0.000000 and E 0.000000 for about 1 second, then is repopulated with the correct lat/lon.

This happens whether or not the Scan APs button is clicked.

Cheers - Jon

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What GPS hardware should I get?

Post by arizonajon » Fri Feb 06, 2015 9:35 am

Another update on my GPS issues:

As I think I mentioned before, I have both native serial ports and serial to USB dongles with either Prolific or FTDI chips.

Yesterday morning, I started up the box using the native serial port COM1. I drove a route to and return from the local Frys' Electronics store, and netted about 2k access points along the way. The whole time I was having the usual "Seconds since..." message even though the lat/lon fields were updating on an every few seconds basis (not great, but ok). When the "seconds since..." for GPGGA reached 30/30, lat/lon would reset to N 0.0000 / E 0.0000 and a second later there'd be the correct lat/lon instead. Unfortunately, for that moment of time, any access points received would get the 0/0 location. If I didn't hear them again, then they'd remain in the Gulf of Guinea. In analyzing the results from the run, about 5% of the surveyed aps were in that part of the Atlantic Ocean.

BTW, at some locations I was getting loop times on the order of 17 to 25 seconds (17000 to 25000 milliseconds). One intersection in particular, if I got caught at the light, the loop times were astonishingly long.

Later in the day, I switched to the Prolific serial to USB adapter. Same setup otherwise. Rebooted the computer to get to a fresh state. Did a drive around town. Within a few minutes the GPS stopped reporting, timed out and got a sound that I assume is generated by VStumb when the GPS goes off line. No way could I get the GPS to return, except by rebooting the box.

Today, I will try the FTDI dongle and see if that's any better.

Cheers - Jon

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What GPS hardware should I get?

Post by marco » Fri Feb 26, 2016 11:41 pm

What do the red lines in ChuckE picture represent? I get red lines too. I at first thought they were driving history but upon closer inspection some zig zag like ChuckE's. What could the problem be?

craig

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What GPS hardware should I get?

Post by pferland » Sat Feb 27, 2016 12:35 am

If you are just sitting in one location and not moving around, it is inherent to GPS. Your position will hop around due to the way GPS works and how many GPS satellites you can see.
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What GPS hardware should I get?

Post by arizonajon » Sat Feb 27, 2016 10:15 am

As Phil indicates, your computed position according to your GPS is a function of how that GPS works.

US GPS is based upon a constellation of spacecraft (s/c) that orbit the earth in six different orbital planes. For a nice animated .gif of the constellation, see

https://upload.wikimedia.org/wikipedia/ ... ionGPS.gif

The lat/lon your receiver indicates is the result of mathematical calculations based upon the offset of the timing codes transmitted by the s/c and received by your GPS. In an ideal environment on the surface of the earth, you see based upon the above .gif that even then the number of s/c seen at any one moment will vary. In theory, all you need are 4 s/c to make a valid lat/lon estimate, but more is always better.

The path between your GPS receiver and all the s/c should be clear and unfettered by trees, buildings, mountains, and other obstacles to the radio transmission from the s/c. Unfortunately, we don't live on an ideal smooth sphere and so the signals that get to your receiver from the s/c are impacted by these obstacles. Even a tree swaying in the breeze can cause some variation, or a truck passing by, and the signal received from any s/c that is not in true line-of-sight (no blockages) will vary in time and in strength. These variations impact the ability of your GPS receiver to calculate a reliable position.

Another and just as important thing here is that the US GPS constellation provides different grades of ultimate position accuracy to civilian vs military. A quick check on Google brings up this statement found on StackExchange.

http://gis.stackexchange.com/questions/ ... acy-of-gps

So, even if you are on an ideal smooth globe, the constellation itself will provide only a 4 meter RMS (7.8 meter 95% Confidence Interval) horizontal (lat/lon) position accuracy. The 7.8 m 95% confidence interval indicates that 95% of the observations that a perfect GPS receiver in an ideal location will calculate, will lie within a 7.8 m radius circle around your true lat/lon. That's about a 25 foot radius circle.

If you stop at a specific location and remain stationary, some GPS receivers use a filtering algorithm and will "decide" that you've stopped and will output only one specific lat/lon until such time that the GPS determines you're moving again. Other GPS receivers will let you have the unfiltered lat/lon estimates even when stationary. This might explain the apparent wandering that was evidenced in ChuckE's picture. Not knowing where his GPS receiving antenna was precisely, and not knowing the local blockages to the necessary s/c, we can't even determine whether his GPS will attempt to filter his position over time.

A long answer, but hopefully it's mostly useful.

Cheers - Jon N7UV

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