GPS Speedometer?

aphesis · 04-04-2004, 06:25 PM

Hi,

Well at the moment the speedometer in my dash doesnt seem to be working and seeing that I have a gps and car pc I was wondering if there was any standalone programs out there that would give me a speedometer?

Magnezium · 04-04-2004, 06:37 PM

SEARCH!!! There's a lot of topics on this!

aphesis · 04-04-2004, 06:51 PM

alright just searched through over 10 pages of search results and didn't find what i was looking for. Mind telling me what the program is called?

Nav_Attack · 04-04-2004, 07:46 PM

don't know of any standalones off hand, but I know that Street Atlas 2004 gives you your speed.

so that means I'm sure you can get one.. if not, get street atlas

you really should get that thing fixed.. or actually not. then you get 1 get-out-of-speeding-ticket free card.

Custommx3 · 04-04-2004, 08:47 PM

I asked the same question a while back regardi ng the same issue.
I emailed him and here was his reponse.

Quote:

The speed info is sent in the nmea stream you get from your GPS reciever.
Its pretty much just one type of stream that gives you that info.

It will look something like this

$GPRMC,224043.051,A,5152.435,N,00159.5732,W,000.0, 238.8,190603,003.7,W*6C

so the 7th or 8th value is the speed in knotts, which in this example is
000.0.

So the conversion to change knotts to mph is

000.0 * 1.151

From what I've seen with just dumping the nmea stream you only get 3 types
of strings coming in. At least from my reciever.

$GPRMC
$GPGSV
$GPGGA

There are a few websites out there that'll tell you everything about the
streams you'd ever want to know. So pretty much the reciever does all the
work, you just have to grab the right string and get the value and do the
math.

Mike

GRUNT · 04-05-2004, 08:31 PM

I have a speedometer running on my test software, uses $GPRMC data.

Give me some time, I will cut out the code and build a standalone Speedo.

If you have a graphic if the Speedo dial, and resolution you want to use.

PM me the graphic.

I can only try!!

god_of_cpu · 04-05-2004, 08:54 PM

Ok, let me get this straight, your speedometer which works off the basic principal of counting how fast your wheels are spinning isn't working so instead of fixing it your gonna rely on a multi billion dollar system of satellites and calculations the must be performed thousands of time a second just to get a speed approximation that isn't anywhere near as accurate... this sound's like a government project to me.

[iG] · 04-05-2004, 10:28 PM

Speedometers lie!!@ GPS doesnt! (Well it does, but its because of the government!)

Chairboy · 04-07-2004, 12:28 AM

While GPS doesn't update anywhere near as fast as your speedometer, it's a far more accurate indicator of your speed then the speedo on your dash. Speedometers have inaccuracies introduced by everything from tire wear to deliberate overreporting to reduce car accidents.

CdRsKuLL · 04-07-2004, 01:00 AM

the only reason I think hes doing it, is because he CAN.. lol and thats without doubt the best reason anyone can have. :-)

Steve

umsam · 04-07-2004, 11:49 AM

aphesis, email me, I have what your looking for. It's still in the test phase but it should do the job. I have a thread going in the OBDII forum, "GPS Speed Display". Take a look.

ukchris · 04-07-2004, 09:39 PM

You can try a prototype I was working on, it's called NMEATest and is here http://www.manwhoring.com/mp3car/ukchris/

Shoryuken · 04-08-2004, 08:36 AM

I have a delorme GPS and Street atlas 2k4, and I've found the speedometer in 2k4 to be a bit 'iffy'.

From 0 - ~60 mph the GPS speedometer matches my car's almost exactly.

From 60 - 70 mph, the GPS reads about 4 mph slower than my car speedometer
From 70 - 80 mph, the gps reads about 7 mph slower than my car speedometer.
From 80 - 90 mph the gps reads about 12 mph slower than my car speedometerr.

I haven't been much over 90mph.

At first, I thought it was my speedometer, but through extensive ghetto-testing (involving my wife following me and 2 cell phones) it appears that my car speedometer is correct ( +/- 1-2 mph).

Anyone else have any problems? This is over a fairly long sample, with the cruise control set in the car, the gps speed is consistantly off at higher speeds.

ukchris · 04-08-2004, 09:06 AM

Or your wife's speedo is just as bad...

How about a timed mile at 90mph? I'd trust the GPS personally, I had heard in the past that car speedos intentionally read over to try and keep you at a more sensible speed - who knows!

Chris.

stevieg · 04-08-2004, 05:10 PM

I've found the same using a road angel (Speed camera GPS databse device) and the GPS speedo is more accurate than the cars. for example... (roughly what i remember)

My old MR2
Car: 30 GPS: 27
Car: 40 GPS: 36
Car: 80 GPS: 72

New Focus
Car: 30 GPS:29
Car: 40 GPS:39
Car: 80 GPS:79

I've also went through a few speed cameras that are dead on the mark trusting the GPS and although the MR2 said I was doing almost 60 the GPS said 50 and I didn't get flashed, so I would go with the GPS rather than than the speedo

ALso remember the speedo can go out by a big amount just by putting the wrong tyres or larger wheels on the car, I too have heard that car manufacturers make the speedo error read over rather than under, maybe this is to compensate for tyre wear?

Also remember the mechanical speedo with work ona logorithmic scale so a little error at 30 will be a massive error at 120 (not that i'd know)

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