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manual:user_guide:tools:altitude [2015/03/31 09:29] – created mstupka | manual:user_guide:tools:altitude [2024/02/16 12:11] (current) – mstupka | ||
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- | ====== Altitude Manager ====== | + | {{ : |
---- | ---- | ||
- | < | ||
- | ....................................... | ||
- | Altitude offset | ||
- | Use altitude offset | ||
- | Define offset between real and GPS altitude | ||
- | Pressure | + | Altitude Manager enables you to fine-tune the altitude values Locus Map receives from your mobile device. It is divided into three main tabs: |
- | Use pressure sensor | + | * **Settings** |
- | Measure precise altitude by pressure sensor | + | * **Offset** |
- | | + | * **Pressure** |
- | Altitude filter | + | ===== Settings ===== |
- | Apply filter | + | Contains general switches of offset and pressure sensor |
+ | ==== Elevation data ==== | ||
+ | <wrap info> | ||
+ | {{ : | ||
+ | * **Don' | ||
+ | * **Optimize GPS values** - uses offline elevation data to optimize GPS altitude values. Optimized elevation has similar accuracy to an average GPS but does not contain serious errors GPS units usually make. Elevation data can be downloaded [[manual: | ||
+ | * **Replace GPS values** - uses offline elevation data only for displaying elevation and calculating elevation gain and charts | ||
+ | <WRAP round alert > | ||
+ | **Warning for pilots**: optimizing or replacing GPS altitude by elevation data is not recommended for activities when you are **not moving | ||
+ | </ | ||
+ | ==== Altitude filter ==== | ||
- | Offset | + | Applies a filter to altitude measurement to reduce deviations. Heavier filters cause less fuzzy altitude values but slower reactions to altitude changes. The scale ranges from no filtration to an ultra-heavy filter. |
- | ........... | + | ===== Altitude offset ===== |
- | Enable | + | {{ : |
- | ... | + | Altitude |
- | Pressure | + | Locus Map can define this offset by three methods: |
- | ............. | + | * **Manual correction** - the basic method used when the exact offset value is known |
- | Enable | + | * **Automatic correction** - a method used in most cases - Locus Map can compute the offset of the whole world from a Geoid model. This method is accurate enough for use in mobile phones and sufficiently precise for all locations (the offset slightly varies based on location). <wrap info> |
+ | * **NMEA correction** - mobile device communicates with GPS unit over special messages called NMEA. These messages contain values of Geoid height that Locus Map can read and apply them to correct this offset.<wrap alert> | ||
+ | |||
+ | ===== Pressure sensor ===== | ||
+ | {{ : | ||
+ | Some devices are equipped with a 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 a certain altitude you can calculate altitude changes between the 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: | ||
+ | * **Automatic** - Locus Map uses GPS altitude or elevation files and current barometric pressure as basic values and relates all other measurements to these values. It also checks measured values in 2-hour intervals and eventually re-calibrates the pressure sensor.< | ||
+ | * **Pressure** - current pressure value at a particular sea level as the reference can be obtained from the Internet. The resulting altitude calculation is also quite accurate but the base pressure changes in time so it can be a problem. | ||
+ | * **Altitude** - uses some other source of ground altitude - external maps, measuring, tourist guide posts, etc. as the reference. Locus Map then calibrates the pressure sensor according to this value. | ||
+ | < | ||
+ | </ | ||
+ | ===== Altitude measurement workflow ===== | ||
+ | Locus Map applies the above-mentioned computations in the following order: | ||
+ | |||
+ | * received altitude from the GNSS unit | ||
+ | * using elevation data files (if enabled) | ||
+ | * using the pressure sensor | ||
+ | * final filtering | ||
+ | If step 2 is missing, the pressure sensor calibration uses directly received altitude values. | ||
+ | |||
+ | <WRAP center round tip> | ||
+ | The **recommended setup** is using elevation data (fully replacing GNSS) without a pressure sensor or using the elevation data only to optimize altitude (useful to eliminate unwanted peaks) + pressure sensor if it's available. | ||
+ | </ | ||
- | Automatic | ||
- | Automatic calibration according to GPS |