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Incorrect Speed after a stop-start movement

Former Member over 15 years ago

Hi all,

I was doing my daily commute to the office and discovered this weird output in the profile after the upload

I noticed the unit was bleeping a lot as I took off and it appeared to be auto-resuming

However, what is strange is the speed around the 2min mark!

Avg Speed: 14.4 mph
Avg Moving Speed: 14.6 mph
Max Speed: 27.7 mph

So the profile chart for speed is incorrect.

Why would this be?

Carl

0 DW152 over 15 years ago

I've seen similar speed spikes on my Garmin fitness devices. GPS isn't the best for calculating maximum speed. The problem comes from the inaccuracy of your position (which is always present), and then calculating the speed based on two inaccurate points (or even just one inaccurate point), which makes the speed calculation a bit noisy. The problem can be mitigated a bit by smoothing or averaging.

0 Former Member over 15 years ago

Well I have to admit I was in a downtown area with tall buildings. It might explain why the unit was making beeping noises for a few moments.

Though my issue is if the device only reports a Max speed of 27.7MPH, where does this ~50MPH spike come from?

The peak of 27.7MPH can be observed around the 8min mark.

0 BBECKER39 over 15 years ago

Which device are you using? A few of our newest devices that actually record speed directly, but the speed graph for other units is generated based on the distance and time for each trackpoint. The max speed is recorded directly in the activity summary.

Poor GPS reception can cause spikes in the post-processed speed graph that aren't reflected in the maximum speed metric.

0 Former Member over 15 years ago

I am using the EDGE 305