View Full Version : How accurate is GPS?
In my "new to me beemer" If I am cruising along the freeway at 100K the GPS is only showing me at roughly 92-93? What do I believe? Mebee it's all a conspiracy? WTF? Rounding errors by NASA again?
I hear that GPS is really not accurate for tracking your speed.
In my "new to me beemer" If I am cruising along the freeway at 100K the GPS is only showing me at roughly 92-93? What do I believe? Mebee it's all a conspiracy? WTF? Rounding errors by NASA again?
100kph. Wot, still running it in? :D
I have no idea about GPS's, I like reading maps. :gomer:
Most speedo's read a little over true speed, especially Italian cars.
Turbodog
01-06-08, 09:27 AM
In my "new to me beemer" If I am cruising along the freeway at 100K the GPS is only showing me at roughly 92-93? What do I believe? Mebee it's all a conspiracy? WTF? Rounding errors by NASA again?
I have a TomTom One XL and it seems to be within 1 mph of my exact speed.
100kph. Wot, still running it in? :D
I have no idea about GPS's, I like reading maps. :gomer:
Most speedo's read a little over true speed, especially Italian cars.
Ummm..... Martin.... BMW is German. :gomer:
nissan gtp
01-06-08, 09:45 AM
In my "new to me beemer" If I am cruising along the freeway at 100K the GPS is only showing me at roughly 92-93? What do I believe? Mebee it's all a conspiracy? WTF? Rounding errors by NASA again?
more likely your speedometer is reading high. typical for an Italian car :rofl:
read here (http://gpsinformation.net/main/gpsspeed.htm)
perhaps 0.5mph accuracy in typical automobile applications would be what you can count on.
lots of details on how it all works on wikipedia (http://en.wikipedia.org/wiki/Gps)
more likely your speedometer is reading high. typical for an Italian car :rofl:
Again.... When did BMW become an Italian marque? :saywhat:
Ummm..... Martin.... BMW is German. :gomer:
It's late and I've had a lot of beer. :p :laugh:
It's late and I've had a lot of beer. :p :laugh:
we also just kicked your arse across the street in the 20/20. :thumbup:
eiregosod
01-06-08, 11:04 AM
GPS is only as accurate as the owners of the system allow.
Andrew Longman
01-06-08, 12:30 PM
I haven't heard about speed, but I've read that the civilian version of the system is accurate to about 50ft (which I could see calculating speed off by a few mph), but IIRC the military system uses additional encrypted signals that make it accurate to just a few feet.
I haven't heard about speed, but I've read that the civilian version of the system is accurate to about 50ft (which I could see calculating speed off by a few mph), but IIRC the military system uses additional encrypted signals that make it accurate to just a few feet.
True but anymore there are several different GPS systems in use worldwide, each with different levels of accuracy. The original plan was for the civilian side of the technology to be "sort of" accurate. But over the years, other systems were put into space and those, while not always available in every local, can be much more accurate. I'm not sure what system is used down under.
rumor also has it that in times of emergency, the military throws in an intentional error.
Talking to a guy in GWI, artillery, he said that you could watch the mil's version change as you took each step.
cameraman
01-06-08, 04:37 PM
The current multisensor gps surveying systems are accurate to less than a centimeter.
High Sided
01-06-08, 05:20 PM
i thought cheesewhiz explained that it's a "bimmer" you're driving? :p
i thought cheesewhiz explained that it's a "bimmer" you're driving? :p
Beat me to it...Bimmer == car, Beemer == bike. :gomer:
http://en.wikipedia.org/wiki/BMW
The term "beemer" started as an acronym for the abbreviation "BMW," adapted from the early-20th century British pronunciation of BSA (as "beeser" or "beezer"), whose motorcycles were often racing BMWs. Over time, the term became closely associated with BMW motorcycles.
In the United States, the term "bimmer" was later coined to refer (exclusively) to BMW automobiles. As such, use of the word "beemer" to refer to a BMW automobile is frowned upon by some BMW enthusiasts,[3] because it is the term used for motorcycles. Although the distinction is completely arbitrary, to this day, the media, movies, and most people still use the term "beemer" to refer to the automobiles.
Cam's Ozzie, so everything's bassackwards for them down under folk. :p
Back on topic, my Tom Tom One seems to be accurate, based the radar speed thingies around our local schools, etc. Based on those, my bimmer's speedo is ~ 5mph low, and the GPS matches that observation. I usually need to go ~25mph for 20mph in a school zone. Go figger.
-Kevin
If you drive fast enough, long enough you'll be able to get some radar verification on those GPS numbers from your local law enforcement for around $50-100.
Unless you get the ticket fixed, then the GPS verification calibration costs increase.
:p
If you drive fast enough, long enough you'll be able to get some radar verification on those GPS numbers from your local law enforcement for around $50-100.
Unless you get the ticket fixed, then the GPS verification calibration costs increase.
:p
Well, I certainly NEVER speed, yo. (awaits lightning) ;)
I shoulda added that the GPS is pretty much exact in my wife's truck. So unless her speedo is off by +5mph..... :\
-Kevin
Well, I certainly NEVER speed, yo. (awaits lightning) ;)
I shoulda added that the GPS is pretty much exact in my wife's truck. So unless her speedo is off by +5mph..... :\
-Kevin
I had the GPS verified this past week. There was one of those speed limit thingos that the cops put out there with the posted speed and a readout that shows what you are doing. I had the speedo at 60 K's and the sign was showing me at ~54k's. So the speedo is definitely slow. :irked:
I had the GPS verified this past week. There was one of those speed limit thingos that the cops put out there with the posted speed and a readout that shows what you are doing. I had the speedo at 60 K's and the sign was showing me at ~54k's. So the speedo is definitely slow. :irked:
Ahh! 22's with spinners will do that Cam! :D
I had the GPS verified this past week. There was one of those speed limit thingos that the cops put out there with the posted speed and a readout that shows what you are doing. I had the speedo at 60 K's and the sign was showing me at ~54k's. So the speedo is definitely slow. :irked:
As I trying to say before; most speedo's do show the car doing faster than it's really doing. The faster you go, the bigger the error.
I would have thought your German car a little more accurate than a 6 kph difference at 60 kph, though.
JT265 is right, check your tyre sizes and compare them to what's on the manufacturer's sticker. If there is a difference, then there's your culprit.
Ahh! 22's with spinners will do that Cam! :D
Spinners? Ppppffffttttt..... Around here you really don't want to stick out in the eyes of the constabulary that much. Believe me!
As I trying to say before; most speedo's do show the car doing faster than it's really doing. The faster you go, the bigger the error.
I would have thought your German car a little more accurate than a 6 kph difference at 60 kph, though.
JT265 is right, check your tyre sizes and compare them to what's on the manufacturer's sticker. If there is a difference, then there's your culprit.
They be the stock. No after market stuff on it. I was at a clients the other day and he was telling me that his wifes, that is older than mine, is out by about the same amount.
ferrarigod
01-14-08, 08:09 PM
most auto makers try to over estimate speed so as not to set people up for tickets or liability. the auto's would rather go over than under.
My friends new Yamaha R6 read 135 on the highway the other day, but we were only doing 121 on GPS. Bikes have a tendency to be off more. His 2002 Yamaha R6 had a speedo helper to adjust, he just hasn't gotten around to buying one for his '08 yeat.
I've had the same issues when switching rims/tyres, but have since gotten it accuratized. :gomer:
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