Garmin GPS sampling rate?

We have a Garmin in our Healey and use it as a speedometer (the Toyota trans/speedometer combination is set up for a 3.54 ratio diff. vs our 3.91, and the speedo itself seems inconsistent, relative to the GPS). However, it seems to jump around more that I would expect (i.e. speed changes of several km/hr without the regular speedometer shifting nor with an obvious change in engine noise etc.).

ANyone know what the sampling rate is that the Garmin would use? (couldn't find anything on the Internet) I'm wondering if perhaps the sample rate isn't high enough to smoothly pick up speed changes. Any other ideas?

Thanks

Doug

I don't know the answer to your question, but the answer to your problem may be to use any of a number of speedometer apps on your smart phone.

I like:

GPS Speedometer and Odometer by Nikhil Kumar
https://apps.apple.com/us/app/gps-speedometer-and-odometer/id1448024273

...and...

Speedometer Simple by Tevfik Yucek
https://apps.apple.com/us/app/speedometer-simple/id939507215

I'm sure there are also many more.

I believe there is a very slight "reporting" delay with any satellite presentation but it is very accurate. More accurate than any car that does not use the original tires and with other modifications. I'm not sure what you meant by jumping around. I would believe the Garmin over 50+ year old technology.

I have a Wahoo device on my road cycle and notice that The speed will jump around when riding along narrow wooded
roads with high trees, it soon corrects itself, I guess when it gets a clearer signal.