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Menu > Settings > GPS and location > Altitude manager
Altitude manager enables to fine-tune obtaining altitude values from your mobile device. It is divided into three main tabs:
Warning for pilots: this method is not recommended for activities when you are not moving on the ground - displayed altitude values are influenced by the ground altitude measuring and calculation
Altitude calculated by internal or external (Bluetooth) GPS unit is related to a different method of referencing the Earth surface than that used in maps. The difference between them is called Geoid height which is distance between Geoid and reference elipsoid.
Locus Map can define this offset by three methods:
Some devices are equipped with barometric pressure sensor. Barometric sensors measure atmospheric pressure very precisely which can be used for calculating relative altitude changes. I.e. if you know certain pressure at certain altitude you can calculate altitude changes between known and current position.
The pressure sensor must be calibrated to a known altitude value so that it can be used for real altitude value calculations. Locus Map offers several methods:
Some devices like e.g. Samsung Galaxy Note II turn off the pressure sensor in standby mode. If you want to use pressure sensor during e.g. track recording, make sure your device maintains the pressure sensor on also when the screen goes off.