Whilst evaluating the data from the APEX Pro, I spotted some inadequacies that I've not seen mentioned before now.

I've written them up for you all (link below) and within the page, I've also provided links to the detailed analysis, etc.

http://logiqx.github.io/gps-guides/devices/coros/apex-pro/data-issues.html

p.s. This also affects the VERTIX in the same way.

Hi,

Just checked out some of the information you shared on the webpage, it's not really clear what kind of tracks you have used for this and what tools (like gps-results etc etc), please keep in mind that the .FIT extension has several field extensions, and not all of that custom data fields are computed correctly when exported to other formats like .sbp or .gpx. For best results , please use the latest version of GPS Results, the latest version of the firmware for Coros and only use .FIT files. 

I used a combination of GPSResults and GPS Speedreader for the analysis. My original observations were in GPSResults then I switched to GPS Speedreader bceause it makes direct comparison of two GPS tracks easier.

All analysis was using the FIT data. I also used the FitCSVTool from Garmin's FIT SDK to examine the contents of the FIT file.

The SDK allowed me to see the precense of the developer fields added by COROS; e.g. COG, SDOP and Sats.

Typo above... should have said "COG, HDOP, Sats"

Hi, just noticed that some additional info has been posted at the initial website, it  would be nice to share the original files from both the Coros devices and the GT31 for comparison, and to share them with Coros also.  Could you send them with wetransfer to info@gps-speedsurfing.com ? 

Hi. I've now added links to the bottom of the relevant pages to help people locate the data.

All of the tracks for this analysis can be accessed via GitHub: https://github.com/Logiqx/gps-guides

The folder containing the tracks for this particular piece of analysis is sessions/20220326/tracks.

:I'd be happy to contact COROS, should I just use support@coros.com?

Sorry, I'm half asleep... sessions/20220327/tracks

I've also put these specific files on Dropbox.

An e-mail should now have been sent to info@gps-speedsurfing.com

Hello! I have compared old good Locosys GT-31, newer GW-60 with Coros Vertix and unfortunately 2 sec, 10 sec, avg and all other speeds differ too much (much lower readings with Coros). Strange that Coros defines itself as Doppler device, but readings are so different...

Speeds are often slightly lower on the COROS (typically 0.1 - 0.3 knots iirc) but on rare occasions they are sometimes a little higher than my GT-31 / GW-60.

The "resolution" issue that I've identified goes some way to explaining this as it is effectively rounding by around 0.1 knots when calculating speeds. If there are multiple interim calculations then these errors could potentially accumulate and I don't know if any smoothing or filtering is going on internally. This will all be masked by the fact that we see the speed results with 2 or 3 decimal digits of "apparent" precision.

I'm going to re-test with the latest firmware (released 4 days ago) and will contact COROS if my Doppler observations still apply; repeated speeds and low resolution.