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| Posted by jiananmail How fast am I traveling Hi everyone When I drive, the speed displayed by TOMTOM XL250 is usually 5km slower than my car speedometer, so basically when my car speedometer shows I am driving at 80, TOMTOM only shows 75. And it is the same for both of my two cars, so which one is more accurate? My cars or the GPS: https://www.gps-data-team.com/convert/speed.php Thanks |
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| Posted by redadder car speedo v gps
Hi, The gps speed is correct. Car speedos always read a bit low to err on the safety side of the fence. 8) |
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| Posted by mikmock Re: How fast am I traveling My Astra estate says I'm doing 10% more than the TomTom and digital speed indicators on the side of the road. |
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| Posted by GDT More... Some posts are not listed here. See all posts here: How fast am I traveling GPS Data Team |
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| Posted by duane4 Re: Bouncing markers / having a coffee at 2.5mph
Many have proven to be inaccurate too, people have beaten them in court.
This isn't correct, they can't be in a geostationary orbit and still cover the polar regions, 20,180 km (12,540 mi) according to wikipedia. IIRC they have an 11 hour orbit.
They can be a lot more accurate and inaccurate then this, but for the most part they generally come within 3m accuracy, the faster you go the more accurate they get (to a point). Also as more birds become available, especially with multi-bands to get round atmospheric delays they're only going to get more and more accurate.
Having a log updated per second can get you off.
What evidence do you have to back this up?
As above the faster you go the more accurate it becomes, walking speeds aren't that great. |
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| Posted by Guest Re: Bouncing markers / having a coffee at 2.5mph
To answer your last question first: My evidence level is ZZ (somewhere in between "I guess" and "I believe"). I trust that you, and anyone else, are much better GPS experts than I am. BUT, the error can only increase as car goes faster. There is no logic that the GPS signal accuracy improves with speeding, BUT on the other side, as my friend explained to me, statistically, the confidence increases as the margin of error decreases. Standing speed 0km/h - GPS shows 2.5 km/h - error = infinite Walking speed 5km/h - GPS shows 2.5 km/h - error = 50% Walking speed 5km/h - GPS shows 7.5 km/h - error = 50% Driving speed 50km/h - GPS shows 47.5 km/h - error = 5% Driving speed 50km/h - GPS shows 52.5 km/h - error = 5% Driving speed 100km/h - GPS shows 97.5 km/h - error = 2.5% Driving speed 100km/h - GPS shows 102.5 km/h - error = 2.5% 1. Any way, GPS does not show the exact speed! GPS software uses averaging to ESTIMATE your speed. Car speedometer uses exact MEASUREMENT to display your speed. In my opinion (evidence level: ZZ) car speedometer wins. 2. Smartphones share processor speed with any background running application. These apps delay internal clock reading and increase the time dependant calculation errors Dedicated GPS units use a dedicated fraction of a processor time to get (more accurate) location reading and use that (more accurate) time for calcs. I checked my speed with an old Apple iPhone, and a new Samsung smartphone. I am deeply sorry to say that Apple wins. Samsung's processor is too busy to give any good (time dependent) reading. (It does not mean that the iPhone is a better phone). Anyway, I prefer my standalone GPS as it does not drain my battery as fast as Samsung/iPhone/any-other-smartphone. |
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| Posted by duane4 Re: Bouncing markers / having a coffee at 2.5mph
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