SatMap - Calibrate your Altimeter
The SatMap Active12 GPS has a built-in Barometric Altimeter, this is more accurate than using a GPS signal only for elevation data.
The default setting in your GPS is for elevation data from the maps.
Each map is supplied with a "height data set" that provides spot heights at regular horizontal intervals (post spacing). Typically these are between 50m-100m. This method works well when the ground is less steep, with fewer cliffs around.
For a more accurate reading you can go into Settings - Elevation and change the Elevation Data Source to Elevation from Pressure.
This setting is especially useful over short periods of time where the weather is relatively stable, since pressure also generally falls when bad weather is approaching.
When using Elevation from Pressure you should calibrate your Altimeter on a regular basis, please click on the link below to watch a video on how to do this.