Anyone knows what gps_metadata.enhanced_speed[m/s] in the .FIT files are used for?

Hi all,

I am analyzing my own .FIT files from my Garmin Fenix 6X Pro Solar Titanium and I have noticed that there are two different entries for enhanced_speed[m/s] and they differs quite a lot. The first is record.enhanced_speed[m/s] and the second is gps_metadata.enhanced_speed[m/s].

record.enhanced_speed[m/s] seems to be the data which is used for Speed and Pace in the watch data fields and also for the diagrams in Garmin Connect mobile app and web.

But, what is gps_metadata.enhanced_speed[m/s] used for? The data in gps_metadata.enhanced_speed[m/s] seems real weird... really low and differs a lot compared to real speed. The record.enhanced_speed[m/s] is also low and does not compare to real speed but its better than the gps_metadata.enhanced_speed[m/s].

I'm having big problems with the Speed and Pace on the device and it seems to be related to this in some way. I know that the accelerometer is involved in the Speed and Pace and that makes the problems even worse.

Anyone who can explain the two different enhanced_speed[m/s] for me?

0 silentvoyager over 4 years ago

I don't see gps_metadata.enhanced_speed in my FIT files - I used two different FIT file viewers to check. What software do you use to extract the data?

0 AndersB over 4 years ago in reply to silentvoyager

I'm using the Java converter (.FIT -> .CSV) in the SDK

0 AndersB over 4 years ago in reply to silentvoyager

Here you can see the differences a bit more clear.

Green lines are calculated GPS Pace (30 sec rolling average) and calculated GPS Distance
Blue lines are the built-in Pace and calculated Distance by Pace
Light orange lines are calculated gps_metadata.Pace (30 sec rolling average) and calculated Distance by gps_metadata.Pace

0 subra over 4 years ago

AndersB said:
But, what is gps_metadata.enhanced_speed[m/s] used for?

Have you enabled DEM in the watch settings?

https://www8.garmin.com/manuals/webhelp/fenix66s6xpro/EN-US/GUID-BC734846-01A7-4F33-86D4-DFBDBC06CDB4.html

0 AndersB over 4 years ago in reply to subra

Dont know which was the latest calibration method ive used. I have tested both DEM and GPS before. Which impact do you mean that it should have on enhanced_speed in .FIT files for the running activities?

0 subra over 4 years ago in reply to AndersB

I don't know how exactly it's calculated and what's the impact, as it's Gamin's trade secret. But I think that the metrics are enhanced by DEM, i.e. GPS Metadata. And as you can see in your table, the enhanced_altitude differ by ~10m and the enhanced_speed is also shifted.

0 AndersB over 4 years ago in reply to subra

Yes, ive noticed that the enhanced_altitude also differs. But record.enhanced_altitude seems more accurate than the gps_metadata.enhanced_altitude. I can calibrate using DEM and do a run tomorrow to see if i notice any difference. If i dont notice anything different i can try to calibrate with GPS and do another run in some days.

I dont think it will have impact on enhanced_speed but its worth a test

0 subra over 4 years ago in reply to AndersB

I assume if you switch to auto calibration or GPS, then the FIT doesn't contain gps_metadata anymore.

0 AndersB over 4 years ago in reply to subra

I already have Auto Calibration During Activity set to "At Start" and Not During Activity set to "On". Had it like that a long time.

0 AndersB over 4 years ago in reply to subra

Did a 10.633 km run after calibration of the altimeter with DEM this morning = gps_metadata still in the .FIT file.

Then I recalibrated the altimeter with GPS and did a short 1 km test run = gps_metadata still in the .FIT file.

So, the calibration type for the altimeter doesn't seem to have any impact on that.