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Ortung (GNSS)

QField kann das interne GNSS (Global Navigation Satellite System, wie GPS, GLONASS, Galileo oder Beidou) nutzen. QField kann auch eine Verbindung mit externen Antennen durch NMEA-Streams über Bluetooth, TCP oder UDP Verbindung herstellen.

GNSS-Geräte sind in der Lage, neben der aktuellen 2D Position auf der Erdoberfläche auch die Höhe zu messen.

Visualisierung

Wenn die Ortung aktiviert ist, wird Ihre Position in blauer Farbe auf der Karte angezeigt. Ihre Position ist entweder als blauer Punkt sichtbar, wenn Sie stillstehen, oder als Pfeil, der Ihre Bewegungsrichtung anzeigt wenn Sie sich bewegen.

Der blaue Strahl zeigt die aktuelle Ausrichtung Ihres Geräts an, wenn das Gerät über einen einen integrierten Magnetkompass verfügt.

Ein Kreis um die aktuelle Position zeigt die Genauigkeit an, die vom Ortungsgerät gemeldet wird.

Konfiguration

Die folgenden Einstellungen sind auf der Registerkarte "Positionierung" der QField-Einstellungen verfügbar.

Messung Wert (M)

Wenn eine Geometrie auf eine Vektorebene digitalisiert wird, die ein M-Wert enthält, fügt QField automatisch Messwerte zu einzelnen Knotenpunkten hinzu, wenn der Koordinatencursor an der aktuellen Position eingerastet ist.

By default, the value will represent the captured position's timestamp (milliseconds since epoch). You can change this value using the combo box in the settings' positioning tab.

The available values to chose from are timestamp, ground speed, bearing, horizontal accuracy and vertical accuracy as well as PDOP, HDOP and VDOP.

Genauigkeitsanforderung

Es kann eine gewünschte Mindestgenauigkeit für Messungen festgelegt werden. Die Qualität wird in drei Klassen angegeben: schlecht (rot), ok (gelb) und ausgezeichnet (grün). Diese Farben werden als Punkt oben auf der GNSS-Schaltfläche angezeigt.

The thresholds can be defined in the settings' positioning tab.

If the Enable accuracy requirement setting is activated, you will not be able to collect new measurements with the coordinate cursor locked to the current position with an accuracy value which is bad (red).

Höhenausgleich der Antenne

Die Höhe des verwendeten Antennenstange kann in den Einstellungen festgelegt werden. Jede gemessene Höhe wird um diesen Wert korrigiert.

Höhenkorrektur / vertikale Gitterverschiebung

Die Höhenwerte können mit vertikalen Raster Grid Dateien korrigiert werden, um orthometrische Höhe zu berechnen.

Vertical grid shift files have to be made available to QField by putting them into the QField app folder <drive>:/Android/data/ch.opengis.qfield/files/QField/proj.

Once the grid shift file is placed there, it is available in QField in the Positioning settings under Vertical grid shift in use.

If you are using altitude correction and an external positioning device is used, consider turning Use orthometric altitude from device off.

Die aktuell unterstützten Dateiformate sind:

  • GeoTIFF (.tif, .tiff)
  • NOAA Vertical Datum (.gtx)
  • NTv2 Datum Grid Shift (.gsb)
  • Natural Resources Canada's Geoid (.byn)

For example: For the transformation from ETRS89 (reference ellipsoid GPS) to NAP (Dutch) users can download the file nlgeo2018.gtx from NSGI and put it in the directory.

Verwendung

Feldarbeit

A short press on the GNSS button will turn on the GNSS and center to the current location once positioning information is available.

Activate edit mode and press on the target button, the cross in the center means it is using GNSS positioning.

A long press on the GNSS button will show the positioning menu.

Inside the positioning menu you can turn on the Show position information which will show the current coordinates which are reprojected into the project CRS along with precision information.

Note

If you see WGS 84 lat/lon information instead of information in your project CRS, you probably have no signal yet.

Verwendung eines externen GNSS Empfängers

Feldarbeit

QField unterstützt die Verbindung zu externen GNSS-Positionierungsgeräten über NMEA-Streams durch Bluetooth-, TCP, oder UDP-Verbindungen.

Unter Einstellungen > Positionierung finden Sie eine Reihe von Schaltflächen zum Hinzufügen, Bearbeiten oder Löschen externer Geräte sowie eine Dropdown-Liste, um zwischen internen und gespeicherten externen GNSS-Geräten zu wechseln.

Zusammenfassung der Verbindungsmöglichkeiten nach Betriebssystem:

Android iOS Windows Linux MacOS
Bluetooth *
TCP
UDP
Serieller Anschluss

(*) Bluetooth support on Windows occurs through the virtual serial port automatically created by the operating system when it connects to the GNSS device.

The NMEA sentences currently supported are GGA, RMC, GSA, GSV, VTG, and HDT.

Note

Make sure no other app like mock location providers are using the same connection.

External receiver log

In Settings > Positioning if you have selected an external receiver as the positioning device, you will find a switch Log NMEA sentences from device to file. If this is activated, all NMEA sentences coming from external positioning devices will be logged to a file.

The logs will be placed in Android/data/ch.opengis.qfield/files/QField/logs.

Note

Be aware that if the log is always turned on, it will fill up all the storage.

Mock location

Feldarbeit

It is possible to provide a mock location via a separate android app to QField. There are several options for this, one of them is Android NTRIP Client.

To use this you have to enable mock locations on your Android device.

Averaged positioning functionality

Feldarbeit

Note

The coordinate cursor must be locked to the current location via the Lock to position button

There is a function that allows you to digitize using averaged positions.

The survey will start by pressing and holding the add vertex button, which will start collecting positions.

While collecting, an indicator will appear on top of the coordinate cursor showing a text reflecting the current number of collected positions. If an averaged position minimum count requirement is active, a progress bar will also be present indicating the progress towards meeting that requirement.

The setting to activate an average position minimum count threshold can be found in QField settings's positioning panel. When active, holding the add vertex button is not required, a short tap on the button will begin the collection of positions and automatically add the averaged position when the minimum count requirement is met.

When using @gnss_* or @position_ variables on averaged positions, the variable will also represent the average over all collected samples.

Project configuration

Vorbereitung am Schreibtisch

Positionierungsvariablen

Du hast Zugriff auf die Positionierungsinformationen über zusätzliche Ausdrucksvariablen, die im Attributformular zugänglich sind. Diese sind nur verfügbar, wenn die Positionierung aktiviert ist.

These variables are commonly used as part of default values expressions for fields to keep track of the quality of individual measured points.

All @position_* variables have a corresponding @gnss_* variable. The gnss variables always report the gnss sensor values, even when the crosshair is not snapped.

  • @position_source_name - The name of the device that gave location information as Um zwischen internen und externen Sensoren zu unterscheiden. Falls die Position manuell gesetzt wurde, und die Position nicht auf die aktuelle Position eingerastet ist, wird der "manual". In case the cursor is not snapped to the position, all other variables will be null, if you need this, use the gnss_ variables statt dessen.
  • @position_quality_description - A human readable and translated string for the quality asvom Sensor gemeldet wird. Z.B. "Fixed RTK". Sie ist nur verfügbar verfügbar, wenn das Fadenkreuz am Sensor eingerastet ist.
  • @position_coordinate - A point with the coordinate in WGS84. Lon, Lat, Altitude as delivered by the sensor. It is only available when the crosshair is snapped to the sensor. - x(@position_coordinate) - IE
  • @position_horizontal_accuracy - The horizontal accuracy of the coordinate (in meters) as reported by the sensor. It is only available when the crosshair is snapped to the sensor. - IE
  • @position_timestamp - The timestamp of the position in UTC as reported by the sensor. It is only available when the crosshair is snapped to the sensor. - IE
  • @position_direction - The direction of movement in degrees from true north as reported by the sensor. It is only available when the crosshair is snapped to the sensor. - IE
  • @position_ground_speed - Groundspeed (in m/s) as reported by the sensor. It is only available when the crosshair is snapped to the sensor. - IE
  • @position_magnetic_variation - The angle between the horizontal component of the magnetic field and true north, in degrees as reported by the sensor. Also known as magnetic declination. A positive value indicates a clockwise direction from true north and a negative value indicates a counter-clockwise direction. It is only available when the crosshair is snapped to the sensor. - IE
  • @position_vertical_accuracy - The vertical accuracy of the coordinate (in meters) as reported by the sensor. It is only available when the crosshair is snapped to the sensor. - IE
  • @position_3d_accuracy - The 3 dimensional accuracy of the coordinate (in meters), 3D-RMS as reported by the sensor. It is only available when the crosshair is snapped to the sensor. - IE
  • @position_vertical_speed - The vertical speed (in m/s) as reported by the sensor. It is only available when the crosshair is snapped to the sensor. - IE
  • @position_averaged_count - This variable holds the number of collected positions from which an averaged position was calculated when digitizing in this mode. For non-averaged positions, the value will be set to 0 (zero). - IE
  • @position_pdop - Position dilution of precision as reported by the sensor. It is only available when the crosshair is snapped to the sensor. - E
  • @position_hdop - Horizontal dilution of precision as reported by the sensor. It is only available when the crosshair is snapped to the sensor. - E
  • @position_vdop - Vertical dilution of precision as reported by the sensor. It is only available when the crosshair is snapped to the sensor. - E
  • @position_number_of_used_satellites - Number of satellites as reported by the sensor. It is only available when the crosshair is snapped to the sensor. - IE
  • @position_used_satellites - A list of satellites in use (pri) as reported by the sensor. It is only available when the crosshair is snapped to the sensor. - array_to_string(array_foreach(@position_used_satellites, @element), ', ') - E
  • @position_fix_status_description - The GPS Fix Status "NoData", "NoFix", "Fix2D" or "Fix3D" as reported by the sensor. It is only available when the crosshair is snapped to the sensor. - E
  • @position_fix_mode - Fix mode (where "M" = Manual, forced to operate in 2D or 3D or "A" = Automatic, 3D/2D) as reported by the sensor. It is only available when the crosshair is snapped to the sensor. - E

Info

  • I: Internal position source E: External (NMEA) position source.
  • Variables that contain satellites are not available on iOS.
Beispiele:
  • when the crosshair is snapped to the sensor - @gnss_horizontal_accuracy > The horizontal accuracy of the coordinate (in meters) as reported by the sensor. - @position_horizontal_accuracy > The horizontal accuracy of the coordinate (in meters) as reported by the sensor. - @position_source_name --> sensor name.
  • when the crosshair is manually moved - @gnss_horizontal_accuracy > The horizontal accuracy of the coordinate (in meters) as reported by the sensor. - @position_horizontal_accuracy > The value is NULL. - @position_source_name > The value is manual.

Vertex logger

It is possible to setup a log layer of the collected vertices. This allows to keep track of meta data for each vertex like GNSS quality attributes and more. To set this up, a point layer can be added to the project and attributes configured to store this information.

Then you should assign the role digitizing logger to a point layer.

Gehe zu QFieldSync > Projekt Einstellungen

Um möglichst effektiv zu sein, sollten die Layerattribute Standardwerte haben, die sich auf die oben aufgezählten Positionsvariablen stützen.