GNSS bundle - Elevations, transformations, providers by alex-cit · Pull Request #727 · MerginMaps/docs

alex-cit · 2026-02-19T19:36:42Z

new page for elevations describing the providers and options
added note to height variables that they may not be available for all providers
List of known supported GPS devices updated: all "yes" for iOS devices set to "yes (mock)", fixed references in the table

Withalion · 2026-03-03T16:34:39Z

src/gis/elevations/index.md

+
+[[toc]]
+
+When collecting data in the field, <MobileAppName /> provides information your position and also elevation. By default, GPS receivers provide an *ellipsoidal height* that is related to the reference ellipsoid. However, for most applications, a *physical height* (also known as height above the sea level) is more appropriate.


Suggested change

When collecting data in the field, <MobileAppName /> provides information your position and also elevation. By default, GPS receivers provide an *ellipsoidal height* that is related to the reference ellipsoid. However, for most applications, a *physical height* (also known as height above the sea level) is more appropriate.

When collecting data in the field, <MobileAppName /> provides information about your position and also elevation. By default, GPS receivers provide an *ellipsoidal height* that is related to the reference ellipsoid. However, for most applications, a *physical height* (also known as height above the sea level) is more appropriate.

Withalion · 2026-03-03T16:36:06Z

src/gis/elevations/index.md

+
+When collecting data in the field, <MobileAppName /> provides information your position and also elevation. By default, GPS receivers provide an *ellipsoidal height* that is related to the reference ellipsoid. However, for most applications, a *physical height* (also known as height above the sea level) is more appropriate.
+
+An *orthometric* height is a physical height referred to a *geoid*, a special surface that is resembles the mean sea level. The difference between ellipsoidal and orthometric height is called the *geoid separation* (also known as geoid height or undulation) and it can be applied to transform these heights.


Suggested change

An *orthometric* height is a physical height referred to a *geoid*, a special surface that is resembles the mean sea level. The difference between ellipsoidal and orthometric height is called the *geoid separation* (also known as geoid height or undulation) and it can be applied to transform these heights.

An *orthometric* height is a physical height referred to a *geoid*, a special surface that resembles the mean sea level. The difference between ellipsoidal and orthometric height is called the *geoid separation* (also known as geoid height or undulation) and it can be applied to transform between these heights.

Withalion · 2026-03-03T17:12:35Z

src/gis/elevations/index.md

+## Internal provider (no external device)
+
+### Android
+In Android, the [internal (fused)](../../field/mobile-app-ui/#gps-settings) GPS provider is used by default. It reports ellipsoidal heights that <MainPlatformName /> transforms to **orthometric heights using the EGM96 geoid model** by default and displays them in the [GPS info panel](../../field/mobile-app-ui/#current-position-and-gps-info).


I'm not 100% sure but using "On Android" feels more natural to me

Withalion · 2026-03-03T17:13:41Z

src/gis/elevations/index.md

+**Custom geoid**: :white_check_mark: It is possible to use the <QGISPluginNameShort /> to [set up a different geoid model](#using-custom-geoid) and transform the elevations to a different vertical reference system.
+
+### iOS
+In iOS, the GPS provider can provide orthometric and ellipsoidal heights.


Same note as with android

Withalion · 2026-03-03T17:29:38Z

src/gis/elevations/index.md

+
+**Position variables**: :white_check_mark: ellipsoidal elevation, :white_check_mark:  orthometric elevation, :white_check_mark: geoid separation values are available and can be stored using [position variables](../../layer/variables/#position-variables).
+
+**Custom geoid**: :white_check_mark: It is possible to use the <QGISPluginNameShort /> to [set up a different geoid model](#using-custom-geoid) and transform the elevations to a different vertical reference system. The defined geoid model is displayed in the <MobileAppNameShort />.


Suggested change

**Custom geoid**: :white_check_mark: It is possible to use the <QGISPluginNameShort /> to [set up a different geoid model](#using-custom-geoid) and transform the elevations to a different vertical reference system. The defined geoid model is displayed in the <MobileAppNameShort />.

**Custom geoid**: :white_check_mark: It is possible to use the <QGISPluginNameShort /> to [set up a different geoid model](#using-custom-geoid) and transform the elevation to a different vertical reference system. The defined geoid model is displayed in the <MobileAppNameShort />.

this should be singular no?

Withalion · 2026-03-03T17:49:37Z

src/gis/elevations/index.md

+
+## Using custom geoid
+
+The geoid model can be specified in [<MainPlatformName /> Project Properties](../../manage/plugin/#mergin-maps-project-properties) in QGIS. The grid shift file then needs to be packages with the project.


Suggested change

The geoid model can be specified in [<MainPlatformName /> Project Properties](../../manage/plugin/#mergin-maps-project-properties) in QGIS. The grid shift file then needs to be packages with the project.

The geoid model can be specified in [<MainPlatformName /> Project Properties](../../manage/plugin/#mergin-maps-project-properties) in QGIS. The grid shift file then needs to be packaged with the project.

I believe we agreed during designing that QGIS plugin will package the grid file behind the scenes, users will just specify which CRS they want to use.

Withalion · 2026-03-03T17:51:03Z

src/layer/variables/index.md

- - `@position_elevation_ellipsoid` - Ellipsoidal height
- - `@position_geoid_separation` - Geoid or quasi-geoid height (undulation)
+ - `@position_longitude` - Longitude 
+ - `@position_elevation` - Orthometric or normal height. *May not be available for some providers, see [Elevations](../../gis/elevations/) for more detail.*


@position_altitude is still supported with the same value as @position_elevation

Withalion · 2026-03-03T17:53:10Z

src/layer/variables/index.md

   - for internal GPS, returns "<NoSpellcheck id="devicegps" />"
-   - for external GPS, returns the MAC address
+   - for [external GPS](../../field/external_gps/), returns the MAC address
+   - for [external GPS](../../field/external_gps/) if mock location is detected, returns "External (Mock)"


this line should be under @position_provider_name

Withalion · 2026-03-03T17:56:27Z

src/layer/variables/index.md

-   - for external GPS, returns the name of the external device
+   - for [external GPS](../../field/external_gps/), returns the name of the external device
 - `@position_provider_address` - GPS device address.
   - for internal GPS, returns "<NoSpellcheck id="devicegps" />"


can be also android_fused & android_gps

Withalion · 2026-03-03T17:58:15Z

src/layer/variables/index.md

-   - for external GPS, returns "external"
+   - for [external GPS](../../field/external_gps/), returns "external"
 - `@position_provider_name` - GPS device name.
   - for internal GPS, returns "Internal"


can be also Internal (fused) & Internal (gps)

alex-cit added 3 commits February 26, 2026 14:09

elevations page

76192ed

spellcheck

f664c21

variables, supported gps

562d0aa

alex-cit force-pushed the iss_701-describing-providers branch from e69ff61 to 562d0aa Compare February 26, 2026 13:31

alex-cit added 2 commits February 26, 2026 20:34

elevations

2bea703

fix

1b012bc

alex-cit requested review from Withalion February 26, 2026 19:39

Withalion reviewed Mar 3, 2026

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GNSS bundle - Elevations, transformations, providers#727

GNSS bundle - Elevations, transformations, providers#727
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alex-cit commented Feb 19, 2026 •

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		[[toc]]

		When collecting data in the field, <MobileAppName /> provides information your position and also elevation. By default, GPS receivers provide an ellipsoidal height that is related to the reference ellipsoid. However, for most applications, a physical height (also known as height above the sea level) is more appropriate.


		When collecting data in the field, <MobileAppName /> provides information your position and also elevation. By default, GPS receivers provide an ellipsoidal height that is related to the reference ellipsoid. However, for most applications, a physical height (also known as height above the sea level) is more appropriate.

		An orthometric height is a physical height referred to a geoid, a special surface that is resembles the mean sea level. The difference between ellipsoidal and orthometric height is called the geoid separation (also known as geoid height or undulation) and it can be applied to transform these heights.


		Position variables: :white_check_mark: ellipsoidal elevation, :white_check_mark: orthometric elevation, :white_check_mark: geoid separation values are available and can be stored using [position variables](../../layer/variables/#position-variables).

		Custom geoid: :white_check_mark: It is possible to use the <QGISPluginNameShort /> to [set up a different geoid model](#using-custom-geoid) and transform the elevations to a different vertical reference system. The defined geoid model is displayed in the <MobileAppNameShort />.


		## Using custom geoid

		The geoid model can be specified in [<MainPlatformName /> Project Properties](../../manage/plugin/#mergin-maps-project-properties) in QGIS. The grid shift file then needs to be packages with the project.

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alex-cit commented Feb 19, 2026 •

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