Every GPS widget I use on my FR935 always shows my altitude based on what my barometer thinks is my current elevation. My known elevation for my residence is 470'. Depending on what my barometer is reading, I've started my GPS at that location with readings of 165' to 600'. I know I can calibrate altitude prior to starting an activity, but if I start an activity elsewhere I have to have a map or look on a website for the known elevation for that start point. It would be so much easier to get a GPS fix and have the elevation displayed from GPS only and then I can calibrate my watch correctly. Is this even possible? Thanks
It seems to me it is not possible with the current SDK to select which source to use.
Elevation is derived from the most accurate source: Barometer or GPS in order of descending accuracy. If no GPS is present, then barometer readings will be used.
I already tried that widget and have the same result. The elevation displayed is from the watch barometric altimeter reading too. Thanks for the suggestion though.
It would be so much easier to get a GPS fix and have the elevation displayed from GPS only and then I can calibrate my watch correctly. Is this even possible? Thanks
If you want to calibrate the altimeter using the current GPS altitude, why don't you just calibrate directly from GPS? Doesn't the F5 have this option? The F3 does.
I have the 935, but I'm being to think my device is faulty. My know elevation at home is 470'. I just got home and my watch reads 431'. I just tried calibrating with GPS and it gave me 433'. I also have the problem I mentioned to you in another post about my altimeter not calibrating to a known saved elevation during an activity. My elevation displays correctly in the activity data field (470'), but it is not calibrating the altimeter even when the activity is saved. Altitude is still showing 431' on the altimeter, and on 3 IQ widgets I have that show altitude. Elevation for the activity shows 470'.
I have the 935, but I'm being to think my device is faulty. My know elevation at home is 470'. I just got home and my watch reads 431'. I just tried calibrating with GPS and it gave me 433'. I also have the problem I mentioned to you in another post about my altimeter not calibrating to a known saved elevation during an activity. My elevation displays correctly in the activity data field (470'), but it is not calibrating the altimeter even when the activity is saved. Altitude is still showing 431' on the altimeter, and on 3 IQ widgets I have that show altitude. Elevation for the activity shows 470'.
The 433' is plenty within normal GPS accuracy. The inaccuracy of GPS altitude measurement is the reason that barometric altimeters are used. So nothing wrong with your experience there.
Regarding not calibrated to a known saved location, there may be two issues:
I don't know the exact behaviour of the 935. There may be differences to what I know from the F3, though it seems that several models share the F3 behaviour.
You mention "saved locations". I have seen different behaviour on saved locations. What seems to work for everyone is doing a manual altitude calibration while the GPS is running (meaning that you should press Start in a GPS activity, make sure you have Green Ring (if the 935 uses that to confirm GPS fix) and then go to Settings and do an altimeter calibration while the activity is still running). This will save the location to a table of known altitudes. This is not the same as a saved location.
But still, I can't explain why the altitude calibration in your last activity is not sticking when you end the activity. Except for my rather weak theory about forced Barometer Mode mentioned in the other thread.
I appear to be posting on the same subject across forums. I'll reply here and then continue on the 935 forum. Anyway, sorry about the confusion. I have both my running start point calibrated to a known elevation, as well as that same spot as saved location. The watch stopped recognizing the saved calibrated elevation from my previous runs. It worked yesterday for my first run and then stopped when I went to do a second run.
So actually what you are looking for is the means to query a data source for actual elevation based on a lat/long fix from the GPS and then update the calibration value of the device for altitude. This would require some coordination between the Connect app and the GPS in the watch, as well as being able query some database on this information (does Garmin have a service for this?). The GPS can do X,Y (Lat/Long) reasonably accurately, but is notoriously bad a Z because you cannot typically "see" satellites at the horizon and below, limiting the amount of accuracy you can derive in Z.
When it comes to elevation based on a barometer, you can only start with what the already inaccurate GPS reports, and try to account for any known weather, and adjust accordingly.
At the end of the day, it comes down to do we really care about absolute elevation, or just elevation change over the event you are trying to record. Adjustments in elevation could also be made after the event using the same proposed query database process then applying an offset to the recorded data.
This is exactly what I'm looking for. I tried contacting the developer to see if it can be made available for the FR935, but it's been awhile since there were any updates and I don't know if the developer still uses it. Is it possible someone can create something similar?
