Varying Heights

[FrequentFlyer]

While out walking today, I placed my A12 on top of a local Trig Point
The local OS map has it at 245 Mtrs
My A12 Barometer Height showed 238 Mtrs (Hot day!)
Switching to GPS mode, showed 244 Mtrs.

Not sure what you can glean from all this !? Just use GPS ?

[dales]

What I can gather from the Garmin wiki site, is that a GPS is good at calculating horizontal distances, but much less accurate at calculating vertical height. So GPS elevation is probably OK at a break stop where the calculations have had time to average out, but not quite as accurate on the march uphill.

In contrast, with the altimeter set to Barometric, then the Garmin unit will start with the known elevation as input by the user at calibration time, and will trend this towards GPS elevation during usage. (Obviously nasty weather changes will inflence these readings).

Finally, if you select a point on the map and click through, you will get the DEM elevation ie the height per the map and its digital interpolation thereof.

Take your pick ! Perhaps use the GPS or Map (DEM) elevation, but not Barometer, as you say !!

Dales
_________________
nuvi 2599LMT-D, oregon 700, basecamp, memory-map.

[dales]

What I can gather from the Garmin wiki site, is that a GPS is good at calculating horizontal distances, but much less accurate at calculating vertical height. So GPS elevation is probably OK at a break stop where the calculations have had time to average out, but not quite as accurate on the march uphill.

In contrast, with the altimeter set to Barometric, then the Garmin unit will start with the known elevation as input by the user at calibration time, and will adjust this elevation for air pressure changes during usage. (Obviously nasty weather changes will inflence these readings).

Finally, if you select a point on the map and click through, you will get the DEM elevation ie the height per the map and its digital interpolation thereof.

Take your pick ! Perhaps use the GPS or Map (DEM) elevation, but not Barometer, as you say !!

Dales
_________________
nuvi 2599LMT-D, oregon 700, basecamp, memory-map.

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