Questions Regarding Altitude Data Fields

[Denis54740]

Hello,
The data fields offer three options for altitude:
1 - Altitude
The altitude of your current position above or below sea level.
2 - GPS Altitude
The altitude of your current position as measured by GPS.
3 - Altitude above ground
The altitude of your current position above sea level.
I tested the first two, and they showed a significant discrepancy.
I need to test this at a location with a known, calibrated elevation.
In the meantime, any explanations would be welcome.
Thank you.

[GPSrChive]

The data fields offer three options for altitude:

There are no altitude data fields for the GPSMAP H1, or other Garmin outdoor handheld devices.

Please see Altitude vs Elevation for more information.

1 - Altitude
The altitude of your current position above or below sea level.

This data field does not exist.

Perhaps you are referring to 'Elevation - The distance between the current location and mean sea level (MSL)'?

Please see GPSrChive > Garmin > How To... > Data Fields for a complete list of available data fields.

2 - GPS Altitude
The altitude of your current position as measured by GPS.

This data field does not exist.

Perhaps you are referring to 'GPS Elevation - The distance between the current location and mean sea level (MSL) using only GPS data'?

Please see GPSrChive > Garmin > How To... > Data Fields for a complete list of available data fields.

3 - Altitude above ground
The altitude of your current position above sea level.

This data field does not exist, and the description is incorrect.

Perhaps you are referring to 'Elevation Above Ground - The distance between your current location and ground level'?

Please see GPSrChive > Garmin > How To... > Data Fields for a complete list of available data fields.

I tested the first two, and they showed a significant discrepancy.

What do you consider a 'significant' value?

'GPS Elevation' is historically less accurate than 'Elevation', which is primarily based on atmospheric pressure readings.

I need to test this at a location with a known, calibrated elevation.

I recommend finding a nearby Benchmark for this. See GPSrChive > Garmin > How To... > Altimeter > Manual Calibration for some calibration tips!

In the meantime, any explanations would be welcome.
Thank you.

Hopefully the responses and links above will help.