Expression Variables in QField

QField supports various expression variables that can be used in forms, expressions, and field defaults. These include the expression variables available in QGIS and additional variables provided by QField to access positioning information and QFieldCloud data.

Positioning Variables

You can access positioning information through additional expression variables. These variables are available only when positioning is enabled.

These variables are commonly used in default values expressions to track the quality and details of individual measured points.

List of Positioning Variables

• @position_source_name - The name of the device providing the location information, as reported by the sensor. It differentiates between internal and external sensors. If the position is manually set and not snapped to the cursor, the source name is "manual". Note: If the cursor is not snapped to the position, all other @position_* variables will be null. Use the @gnss_* variables instead.
• @position_quality_description - A human-readable and translated description of the quality as reported by the sensor (e.g., "Fixed RTK"). Available only when the crosshair is snapped to the sensor.
• @position_coordinate - A point containing the WGS84 coordinate (longitude, latitude, altitude) as delivered by the sensor. Available only when the crosshair is snapped to the sensor.
• @position_horizontal_accuracy - The horizontal accuracy of the coordinate (in meters), as reported by the sensor. Available only when the crosshair is snapped to the sensor.
• @position_timestamp - The timestamp of the position in UTC, as reported by the sensor. Available only when the crosshair is snapped to the sensor.
• @position_direction - The direction of movement in degrees from true north, as reported by the sensor. Available only when the crosshair is snapped to the sensor.
• @position_orientation - The orientation of the device itself, regardless of its movement, relative to true north (from 0° to 359°).
• @position_ground_speed - Groundspeed (in m/s), as reported by the sensor. Available only when the crosshair is snapped to the sensor.
• @position_magnetic_variation - The angle between the magnetic field's horizontal component and true north (magnetic declination). A positive value indicates a clockwise direction from true north; a negative value indicates counter-clockwise. Available only when the crosshair is snapped to the sensor.
• @position_vertical_accuracy - The vertical accuracy of the coordinate (in meters), as reported by the sensor. Available only when the crosshair is snapped to the sensor.
• @position_3d_accuracy - The three-dimensional accuracy of the coordinate (in meters), as reported by the sensor. Available only when the crosshair is snapped to the sensor.
• @position_vertical_speed - The vertical speed (in m/s), as reported by the sensor. Available only when the crosshair is snapped to the sensor.
• @position_averaged_count - The number of collected positions from which an averaged position was calculated. If not averaged, the value is 0 (zero).
• @position_pdop - Position dilution of precision, as reported by the sensor. Available only when the crosshair is snapped to the sensor.
• @position_hdop - Horizontal dilution of precision, as reported by the sensor. Available only when the crosshair is snapped to the sensor.
• @position_vdop - Vertical dilution of precision, as reported by the sensor. Available only when the crosshair is snapped to the sensor.
• @position_number_of_used_satellites - The number of satellites used by the sensor. Available only when the crosshair is snapped to the sensor.
• @position_used_satellites - A list of satellites in use (PRI), as reported by the sensor. Available only when the crosshair is snapped to the sensor.
• @position_fix_status_description - The GPS fix status ("NoData", "NoFix", "Fix2D", or "Fix3D"), as reported by the sensor. Available only when the crosshair is snapped to the sensor.
• @position_fix_mode - The fix mode ("M" = Manual, "A" = Automatic), as reported by the sensor. Available only when the crosshair is snapped to the sensor.

Info

• I: Internal position source, E: External (NMEA) position source.
• Variables containing satellites are not available on iOS.

Note

All @position_* variables have a corresponding @gnss_* variable. The gnss_* variables always report the GNSS sensor values, even when the crosshair is not snapped. - When the crosshair is snapped to the sensor: - @gnss_horizontal_accuracy > Reports the sensor's horizontal accuracy (in meters). - @position_horizontal_accuracy > Reports the same value as the corresponding gnss value. - @position_source_name > Reports the sensor name. - When the crosshair is manually moved: - @gnss_horizontal_accuracy > Reports the sensor's horizontal accuracy (in meters). - @position_horizontal_accuracy > The value is NULL. - @position_source_name > The value is manual.

QFieldCloud

For QFieldCloud users, two expression variables can be used in forms or default values:

• @cloud_username - Returns the name of the currently logged-in QFieldCloud user.
• @cloud_useremail - Returns the email address of the currently logged-in QFieldCloud user.