Zany script idea

DL33T · 05-04-2003

I'm just curious as to if this sort of thing is feasible... Most handheld GPS units have built-in compasses - do these usually send compass bearings over the serial interface as well?

If so, here's the idea - mount the GPS on a rotating stand with a small yagi antenna. In theory, as the GPS/antenna mount is rotated a script could match the compass data with the SNR and Lat/Long of each AP hit to triangulate the exact position and strength of each antenna. One could either rotate the mount as they drive, or stop every few blocks or so and do a few sweeps.

Now of course, such a mount would draw plenty of unwanted attention if mounted on a roof, and it wouldn't be too easy to set up, but is such a thing even possible?

Madhadder · 05-05-2003

Gonna jump out on this one...

As far as I know And have seen, the GPS's that Output
NMEA via a cable DO NOT output a seperate signal for
a compas heading. It's not part of the NMEA protocol.

The software routing/location software you use, basis
the direction traveling/heading by the changes in the
location data "NMEA Strings" and plots it..

It was a nice Idea, but it won't work...

nashr · 05-05-2003

Not only is the compass software-based, but it doesn't take into account the orientation of the device. In other words, if you turn in a circle, the "compass orientation" won't account for this. It takes your direction of movement and plots the compass direction from that.

Thorn · 05-05-2003

This idea just keeps coming back from the dead. Just like some cheezy horror film villain.

Every three to six months. someone has this idea. DL33T if your serious, you might want to search on "fox hunt" and "DFX". Hams do this type of thing with antenna arrays, rather than a rotating yagi. There is plenty of stuff on the web regarding doing this at 2m. Some hams even have LED displays that look like a radar screen. It shows distance, bearing and RSSI. You'd have to change it to 2.4GHz, put the principles are the same.

DL33T · 05-09-2003

I figured it was something like that, nashr...

And Thorn, it sounds interesting, I'll have a look.

marius · 05-10-2003

Some GPS units (for example the eTrex Summit and Vista) do have a magnetic compass built in. They even output NMEA reporting the heading ($HCHDG sentence). NetStumbler ignores this.

05-04-2003	#1 (permalink)
DL33T Registered Member Join Date: Jan 2003 Location: Florida Posts: 14	Zany script idea I'm just curious as to if this sort of thing is feasible... Most handheld GPS units have built-in compasses - do these usually send compass bearings over the serial interface as well? If so, here's the idea - mount the GPS on a rotating stand with a small yagi antenna. In theory, as the GPS/antenna mount is rotated a script could match the compass data with the SNR and Lat/Long of each AP hit to triangulate the exact position and strength of each antenna. One could either rotate the mount as they drive, or stop every few blocks or so and do a few sweeps. Now of course, such a mount would draw plenty of unwanted attention if mounted on a roof, and it wouldn't be too easy to set up, but is such a thing even possible? __________________ o_O

05-05-2003	#3 (permalink)
nashr Uber Geek Join Date: Aug 2002 Location: Virginia Posts: 1,615	GPS Compass Not only is the compass software-based, but it doesn't take into account the orientation of the device. In other words, if you turn in a circle, the "compass orientation" won't account for this. It takes your direction of movement and plots the compass direction from that. __________________ Help! I've been Simpsonized!

05-05-2003	#4 (permalink)
Thorn Did you do the math? Join Date: Apr 2002 Location: Villa Straylight Posts: 10,096	This idea just keeps coming back from the dead. Just like some cheezy horror film villain. Every three to six months. someone has this idea. DL33T if your serious, you might want to search on "fox hunt" and "DFX". Hams do this type of thing with antenna arrays, rather than a rotating yagi. There is plenty of stuff on the web regarding doing this at 2m. Some hams even have LED displays that look like a radar screen. It shows distance, bearing and RSSI. You'd have to change it to 2.4GHz, put the principles are the same. __________________ Thorn "I'm The Doctor. I'm a Time Lord. I am from the planet Gallifrey in the constellation Kasterborous. I'm 903 years old and I am the man who is going to save your lives and all 6 billion people on the planet below... You got a problem with that?"

05-09-2003	#5 (permalink)
DL33T Registered Member Join Date: Jan 2003 Location: Florida Posts: 14	I figured it was something like that, nashr... And Thorn, it sounds interesting, I'll have a look. __________________ o_O

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05-05-2003	#2 (permalink)
Madhadder General "Noob Basher" Join Date: Apr 2002 Location: Munich, Germany Posts: 1,620	Gonna jump out on this one... As far as I know And have seen, the GPS's that Output NMEA via a cable DO NOT output a seperate signal for a compas heading. It's not part of the NMEA protocol. The software routing/location software you use, basis the direction traveling/heading by the changes in the location data "NMEA Strings" and plots it.. It was a nice Idea, but it won't work...

05-10-2003	#6 (permalink)
marius It's all my fault Join Date: Apr 2002 Location: Northern California Posts: 108	Some GPS units (for example the eTrex Summit and Vista) do have a magnetic compass built in. They even output NMEA reporting the heading ($HCHDG sentence). NetStumbler ignores this.