GPS giving wrong coordinates!

bmw318ISCoupe · 01-01-2006, 01:15 AM

I have a rather unusual problem that started when I was trying to import POIs over wireless networks in my hometown kirkenes in norway. I am using mapmonkey and netstumbler with xport to split com-signals. Everything works fine with mapmonkey giving me the right coordinates, but netstumbler says that my wireless network at home is some 34km away. I discovered this when i was trying to use nmeaGE and google earth, and the map showed that i was in russia. That could problarbly give me some problems when they see my log-file and they ask for a valid visa for the trip

or maybe it could give me a perfect alibi

Uh Uh Uh, You didn't say the magic word !

anyways, does anyone know what could be wrong? could it be xport? i find it weird that mneaGE and netstumbler get wrong coordinates, and mapmonkey get correct coordinates at the same time. Have attached a pic with netstumbler log and the poi from my house with the correct coordinates. HELP PLEASE!

Genesisfactor · 01-01-2006, 02:44 AM

You haven't ****ed off any major governments lately, have you?

Something like that means an algorithm wasint copied right or corrupted. This was a project in some people in my linear algebra classes did (they created and analyzed the GPS matrix algorithms. Don't ask me, i did matrix encryption). Install it on another PC and see if the same thing happens. Its the only way. Its amazing what one wrong bit will do to a complex calculation!

markbuts3 · 01-01-2006, 10:38 AM

Those co-ordinates aren't that far apart...

69° 41.564' = 69.69273 29° 59.694' = 29.9949

bmw318ISCoupe · 01-01-2006, 12:27 PM

Not so far away, no, but 34 km misguidance could give me a problem when i am trying to find a wireless network

could it be xport messing up the coordinates? anyone wxperiences the same?

Curiosity · 01-01-2006, 12:52 PM

XPort doing what?

No way!

Run netstumbler with XPort and look at the coordinates, then run it again without XPort, connecting directly to the GPS. You should see the same exact values. If not, tell me.

bmw318ISCoupe · 01-04-2006, 01:34 PM

Its not xports fault, in the pic you see that mapmonkey and nmeaGE has the right coordinates, and netstumbler has got the wrong coordinates. When I tryed to not use xport, only netstumbler, it gave the exact same coordinates as before. There must be something wrong with netstumbler i guess...

what could it be?

Curiosity · 01-04-2006, 03:43 PM

The GPS output is in degress + 2.3 places for minutes. When converting time to degrees some programmers round and some don't so there will always be a small difference. I wouldn't think that's a big deal.

Rob Withey · 01-04-2006, 04:10 PM

Quote: Originally Posted by bmw318ISCoupe

netstumbler has got the wrong coordinates.
what could it be?

Those coordinates are pretty much the same. One is expressed as degrees, one is expressed as degrees and minutes:

69.6621383333333 degrees = 69 degrees 0.6621383333333*60 minutes = 69 degrees 39.72829999999 minutes.
29.982055 degrees = 29 degrees, 0.982055*60 minutes = 29 degrees 58.9233 minutes.

Rounding explains the very small discrepancies as Curiosity said.

bmw318ISCoupe · 01-05-2006, 09:51 AM

Ahh, I see! Thanks for the help!
So if I want to write the coordinates from netstumbler expressed as degrees n minutes in just degrees, you just take the numbers after the point, and divide it with 60?

Something like this:
69 degrees 39.728299999 minutes =
69 + (39,728299999/60) =
69 + 0,662138333 =
69,662138333

Is there a web page or app that does this automaticly, or is there a option in netstumbler to show the coordinates as degrees?

DeltaFX · 01-05-2006, 04:06 PM

Officially, NEMEA coords are in dddMM.mmmm

ddd :degrees (can be 1, 2 or 3 digits long)
MM is a fixed-length number of minutes
mmmm is 1/10000 of a minute.

To convert to degrees :

DD:= Trunc(DM /100.000000);
MM:=DM - (DD*100.000000);
DD:=DD + (MM/60.000000);