GPSrChive Discussion Forum

Regarding the issues being reported with much higher Ascent and Descent readings, after doing some testing today on a route that I have done many times and looking back at past recordings that I could find, I personally feel that the issue is firmware related rather than hardware.
For example the 14.50 mile hike that I do, should be looking at digital map data, dem data etc around 2400 feet ascent and 2450 descent.
My recordings as follows:
April 2023 fw 4.80
Ascent 2677 Descent 2759
July 2023 fw 5.30
Ascent 2020 Descent 2080
November 2023 fw 6.60
Ascent 3964 Descent 4029
February 2024
Ascent 3707 Descent 3638

Over all of these dates bar February 2024 I have also used a Garmin Enduro 2 & Fenix 7x watch and they both recorded give or take 50 feet either way the same figures as the digital map / dem data.

the last hike on Monday at the seaside and lagoon, total real ascent 10m, the 67 displays 49m. My setting has not changed. Version 7.60.

Ahh don't think it will ever change, as Garmin refuse to accept it is a fault and it is perfectly normal.

RunnerAndrew wrote: ↑Sun Feb 04, 2024 3:14 pm Over all of these dates bar February 2024 I have also used a Garmin Enduro 2 & Fenix 7x watch and they both recorded give or take 50 feet either way the same figures as the digital map / dem data.

One major difference between the GPSMAP and Garmin smart watches is that the watches allow calibration of the altimeter based on DEM data, either from on device map or from internet (connected DEM).

Speculating, that could that be an explanation why the ascent/descent data on the Fenix / Epix / Enduro is more accurate than that from the GPSMAP? If so it would be nice if Garmin ported that functionality to the GPSMAP...

JungleJim wrote: ↑Wed Feb 07, 2024 2:12 pm One major difference between the GPSMAP and Garmin smart watches is that the watches allow calibration of the altimeter based on DEM data, either from on device map or from internet (connected DEM).

Calibration and the method of calibration do not affect the overstatement of data on increases
and decreases when automatic calibration is used (once).

The altimeter records changes in atmospheric pressure due to changes in altitude.

What is the best calibration setting to use, Continuous or Once? And is there any specific kind of environment where one works better than the other?

During not very long trips, automatic calibration (once) is more beneficial, especially if the trip falls within the daily pressure cycle.

During long-hour trips, continuous calibration may prove useful - altitude data based on the GPS signal can correct the altitude caused by the daily pressure cycle.

However, in areas with difficult access to a GPS signal, continuous calibration is not recommended.

You can calibrate manually based on a map with DEM data or based on other sources.

JungleJim wrote: ↑Wed Feb 07, 2024 2:12 pm

RunnerAndrew wrote: ↑Sun Feb 04, 2024 3:14 pm Over all of these dates bar February 2024 I have also used a Garmin Enduro 2 & Fenix 7x watch and they both recorded give or take 50 feet either way the same figures as the digital map / dem data.

One major difference between the GPSMAP and Garmin smart watches is that the watches allow calibration of the altimeter based on DEM data, either from on device map or from internet (connected DEM).

Speculating, that could that be an explanation why the ascent/descent data on the Fenix / Epix / Enduro is more accurate than that from the GPSMAP? If so it would be nice if Garmin ported that functionality to the GPSMAP...

Dem is all good if you're right near the contour line with the elevation but sometimes if you're on top of big flat hill top and the contour line isn't near you, you can suffer with the elevation being out.

You are considering maps with contours (isohipps), and JungleJim mentioned maps with DEM
data that can be based on as little as a 1m x 1m grid.

In maps, DEM data is probably based on a 100 m x 100 m grid or 50m x 50 m.

Years ago I had a 6000m Thommen temperature compensated altimeter. Now I wish I hadn’t sold it. I would calibrate it or check it against a known position on a contour line when feasible. It was very accurate. Too bad it appears Garmin can’t replicate it. Just goes to show new or electronic isn’t always better.