Lee_M
Guru
scrap that just saw roberts reply, so over 50 miles the difference is less than 500 yards?
personally I think thats accurate enough for me
GPS How Accurate?
- Thread starter Rob Brookes
- Start date
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scrap that just saw roberts reply, so over 50 miles the difference is less than 500 yards?
personally I think thats accurate enough for me
OP
OP
Rob Brookes
Active Member
Tha'ts more than accurate enough for me and will free up some space for the winter light I have my eyes on.
fossyant
Ride It Like You Stole It!
- Location
- South Manchester
What you do is get a GPS with cadence and speed sensors too, then it's really accurate.
I calibrated my VDO C5 from my Garmin 800 and kept tweaking it till it would almost match and I find that I rarely get a difference of two tenths of a mile regardless of the distance and at the most its around half a mile difference , even on a 200+ miles ride, its always around the same error. Yesterdays very short ride, my "800" recorded 34.32 miles and the VDO, 34.15 miles. Also I only use GPS on the "800" and not the sensor on the back wheel/chain stay to record speed.
Rob3rt
Man or Moose!
- Location
- Manchester
I was just stating the relative advantages of either technology! Not arguining that GPS is not good enough. However, GPS is notorious for spikes in speed and other glitches, cutting corners or over shooting on tight bends etc. So depending on the route, the error exhibited with a GPS can be substantial, example, I have rode a 5km (3.1 mile) lap which is quite twisty a couple of times, the GPS has quoted distances as low as 2.67 mile and on average about 2.8 mile. I know the distance is 5km around the racing line (shortest possible way round), as it is a certified loop by the UKA for running races (which I organise, so I know I went the right way). That's a substantial error!
It really depends on the course!
Some images for your consideration!
Often software like Garmin connect force the route drawn onto nearest roads, making it look ok, when actually it was some way off, here is a non corrected trace:
I use the option Fossy refer's to, Garmin with a GSC10 sensor! Best of both worlds!
If anyone is interested there used to be a lot of technical specs about how the garmin calculated GPS available on the net. You can even do the maths of it if you like with the six well known parameters for errors. Not my kind of thing though.
Rob3rt
Man or Moose!
- Location
- Manchester
400bhp
Guru
From your posts you seem to have a similar thought process to me and guessed you would be doing something mathematical related.
Not that having a similar thought process to me is something to be proud of
