So I am the seaside at the moment and wanted to calibrate the altitude. I expected the GPS to report a 0 or 1 m altitude, bu i'm getting -12. Anyone know what the issue is here?
I've had that too, I've also had the "calibrate with GPS" be inaccurate in other locations (away from the sea) but I have no idea why, other than to assume that the GPS calibration isn't always accurate. I've had it where commencing an activity with auto correct enabled has given me an elevation of 100m when the correct altitude was more like 24m, I assumed that this was because the watch didn't have a clear view of the sky but it has also happened when it has so I have turned auto correct off.
Sorry its called "Auto Cal" No, when you start an activity if you have "auto cal" enabled the GPS will set the altitude based on GPS position at the start of the activity. If you leave it turned off then it will stick with what it was already showing. I have found auto cal not to be reliable.
So I am the seaside at the moment and wanted to calibrate the altitude. I expected the GPS to report a 0 or 1 m altitude, bu i'm getting -12. Anyone know what the issue is here?
From the garmin support:
With the Auto Calibration feature turned on, the altimeter accuracy can range from +/- 50 to 125 feet (same as GPS elevation). With a strong GPS connection with WAAS, it's possible to obtain an accuracy of +/- 25 to 50 feet.
When manually calibrating (Auto Calibration off) to a known elevation it is possible to achieve accuracy of +/- 10 feet for the first 15 minutes. If needing accurate elevation, it is recommended to calibrate the altimeter hourly to maintain its accuracy because of possible pressure changes.
_______ And I read in some web about altimeter accuracy on watch: Expect the general accuracy +/- 15m. So when you lying on beach seaside, expect the elevation -15 to 15m :)
Well, the primary question is: why do you expect it be it at 0 at all? There is no such thing as a common global sea level. Sea levels at different places differ. This has been been an issue in constructions between different countries (e.g. tunnels)
What is considered 0 altitude even differs from country to country. E.g. Germany's 0 (reference is in Amsterdam) is not the same as Switzerland's 0 (reference is in Marseille) . Although they are neighbors.
This article describes how this problem is solved in GPS and this also tells us why it can be fine to have negative readings:
