Multiple GPS inputs for better accuracy/speed?

**Marzer** · 07-31-2009, 12:17 PM

Hey guys,

I'm liking my BU-353, but it'd be nice if I could make it update a bit faster. Is it possible to add another one (seeing as they're pretty cheap) and average out the inputs for a better or faster feed? I noticed that GPSGate can multiplex inputs, but i'm not sure if this is merely a compression thing or if this is what I'm after.

Any ideas?

**DarquePervert** · 07-31-2009, 01:38 PM

I sincerely doubt that two GPS units is going to get you a faster lock.
You'll probably have better results moving your BU353 to a location that has a better view of the the open sky. If it's in a window that has a metallic tint, that could affect the operation of the GPS as well.

**Marzer** · 07-31-2009, 01:41 PM

Yea, I'm definitely not ruling that out. Currently it's on the parcel shelf and the rear window has a slight tint, so I'll have to do some testing.

The idea of multiple inputs is pretty sexy though, mainly just curious if it would work.

**malcom2073** · 07-31-2009, 01:43 PM

DP: That's not what he asked.

You could average the inputs, but if you average two inputs with +/- 10m accuracy, you're gonna have a result of +/- 10m accuracy. It would be faster sure, but no better.

**JC-S60** · 07-31-2009, 01:57 PM

I even doubt it would be faster as they run at 1Hz... You should get them to power up exactly 500 millisec apart to double the updating speed (and then write some software that takes both streams and outputs to one virtual serial port).
Oh, and your nav software has to support updates of 2Hz for it to work too

Try it and let us know as it sounds like a fun thing to do!

**psyrex** · 08-02-2009, 04:04 AM

Sure, there are always faster stuff. I was thinking of doing that myself for better accuracy. You can try a 10Hz module, hook it up to something like an arduino to average it all, but there's one giant limitation: your navigation software. If you're using something consumer like iGuidance, the software only checks once a second, so it doesn't matter however fast your gps unit is.

**DeltaFX** · 08-02-2009, 04:17 AM

yeah, but with a 10Hz you can write a piece of code to split five 2 Hz nmea sentences to 5 different apps, or select the best set (lowest hdop) to send to your 1hz app out of ten, or....

**TheSovereign** · 08-02-2009, 11:52 AM

Originally Posted by DeltaFX

yeah, but with a 10Hz you can write a piece of code to split five 2 Hz nmea sentences to 5 different apps, or select the best set (lowest hdop) to send to your 1hz app out of ten, or....

there are already port splitters such as Xport which can send NMEA sentences to multiple applications, and it doesn't matter what GPS speed is... or am I missing something here?

**2k1Toaster** · 08-02-2009, 12:14 PM

Originally Posted by TheSovereign

there are already port splitters such as Xport which can send NMEA sentences to multiple applications, and it doesn't matter what GPS speed is... or am I missing something here?

Only thing I can see you are overlooking is the programatically choosing which NMEA data to send to the program instead of the one closest to the time the app reads the serial port.

So if you have 8 readings all somewhat in the same spot or in the same line, and then 2 which are very far off (maybe a big tree or a bridge or something obstructed the time signals), then you would choose to send one of the 8 good ones. Regularly it would just be luck of the draw and you could get a bad one.