index.md

description	Mergin Maps variables (username, user email or project name) or GPS position variables can be used in QGIS expressions and as default values in forms.

Variables

There are some useful variables that can be used as default values.

Here you can find the lists of:

• project and user variables introduced by that can be used to record information related to workspace, project or users
• position variables that can be used to record GPS information

Project and user variables

The adds several variables that can be used in QGIS expressions:

Variable name	Type	Sample value	Description
@mm_full_name	string	Joe Schmoe	Full name of the currently logged in user, blank if the full name is not set
@mm_username	string	joe-schmoe	Username of the user currently logged in to
@mm_user_email	string	joe.schmoe@mail.com	Email of the user currently logged in to
@mm_url	string	https://app.merginmaps.com	URL of the service
@mm_project_name	string	My project	Name of the active project
@mm_project_full_name	string	my-team/My project	Workspace and project name joined with a forward slash
@mm_project_version	integer	9	Current version of the active project

A common use case is to use @mm_username or @mm_user_email as the default value for one of the fields in a survey layer to automatically track who has added (and/or modified) a particular record.

::: tip mergin_ variable names still work! QGIS variables listed here previously used the prefix mergin_. Now we use the prefix mm_ standing for .

Both naming options are functional and will continue to work in the future: @mergin_user_email and @mm_user_email provide the same value when used in QGIS expressions. :::

Position Variables

With , it is possible to access GPS information using extra position variables. Note that location permission has to be allowed and location service enabled.

Extra position variables can be used as default values in feature forms.

Variable name	Type	Description
@position_coordinate	geometry	A point with the coordinates in WGS84
@position_latitude	decimal	Latitude
@position_longitude	decimal	Longitude
@position_elevation	decimal	Orthometric or normal height
@position_elevation_ellipsoid	decimal	Ellipsoidal height
@position_geoid_separation	decimal	Geoid or quasi-geoid height (undulation)
@position_direction	integer	The bearing measured in degrees clockwise from true north to the direction of travel
@position_ground_speed	decimal	The ground speed, in meters/sec
@position_vertical_speed	decimal	The vertical speed, in meters/sec
@position_magnetic_variation	decimal	The angle between the horizontal component of the magnetic field and true north, in degrees. Also known as magnetic declination. A positive value indicates a clockwise direction from true north and a negative value indicates a counter-clockwise direction.
@position_horizontal_accuracy	decimal	The accuracy of the provided latitude-longitude value, in meters
@position_vertical_accuracy	decimal	The accuracy of the provided altitude value, in meters
@position_from_gps	Boolean	True if recorded/edited feature's geometry corresponds with current user's position (position marker has the same location as the crosshairs marker)
@position_satellites_visible	integer	Number of visible satellites
@position_satellites_used	integer	Number of satellites used to calculate the position
@position_gps_fix	string	GPS fix, e.g. "RTK float"
@position_gps_antenna_height	decimal	Antenna height as defined in GPS settings
@position_provider_type	string	GPS device type (for internal GPS, returns "internal", for external GPS, returns "external")
@position_provider_name	string	GPS device name (for internal GPS, returns "Internal", for external GPS, returns the name of the external device)
@position_provider_address	string	GPS device address (for internal GPS, returns "", for external GPS, returns the MAC address)
@position_hdop	decimal	Horizontal dilution of precision (HDOP)
@position_vdop	decimal	Vertical dilution of precision (VDOP)
@position_pdop	decimal	Position (3D) dilution of precision (PDOP)

:::tip Dilution of precision (DOP) is a useful value that reflects the confidence level of achieved position precision. In addition to the horizontal and vertical accuracy, the appropriate DOP value (horizontal, vertical, or 3D) can be used to assess the overall quality of your survey accuracy.

You can read more about this topic e.g. on Wikipedia. :::