Vector Layer Settings
Most of the settings which QGIS offers are directly supported by QField without any extra effort.
All style settings from QGIS are directly supported by QField. This includes all renderer types like graduated, categorized, rule based, 2.5D as well as data defined symbology.
In QField, objects are identified with a name. The expression to generate this name can be defined by opening the attribute table in QGIS and switching to the form view. Choose the appropriate field or an expression in the list there. Starting from QGIS 3, this can be done directly from the :menuselection:`Vector Layer Properties --> Display` page.
The display expression is also used to search in layers.
Read only, non-identifiable and searchable layers
Some layers in a project are just there for pure visual purpose. Such layers should not show up when a user taps somewhere to identify objects.
Some other layers serve as source of information and shouldn't be modified by the user. It is possible to protect layers from editing attributes or adding and deleting features.
It is also possible to configure which layers are searchable.
To configure identify, readonly and searchable behavior, go to the :menuselection:`Project --> Project Properties --> Identify Layers` page and activate the checkboxes to match your desired behavior.
Forms and Fields
QField creates forms similar to, but not equal to QGIS.
Suppress Feature Form
The setting suppress feature form is directly applied to the QField form.
The field widgets from QGIS are supported on a best effort basis.
|External Resource||~||This field is combined with camera integration. Only images can be viewed so far. :ref:`make_it_grow`|
Drag and drop designer forms
Groups and Tabs from Drag and Drop designer forms are supported.
Groups can be hidden based on an expression. This is useful when certain attributes are only required under certain conditions. As an example imagine mapping trees. Some of them might have a disease and you have a list of possible deseases. To not clutter the form with many fields, make a group and configure a visibility expression for a group "diseases". Add a field "desease" with a checkbox. Only when the checkbox is checked, the list of diseases will be available to the user.
Attribute fields can have constraints attached. Constraints are expressions that needs to
1) in order to be able to save the form. Constraints
are configured on a per-field basis and a description can be added that will be shown to the
user if a constraint is not satisfied.
Common use cases
You cannot enter an elevation value higher than the highest mountain in this country.
"elevation" < 5000
It is required to fill in an identifier.
"identifier" IS NOT NULL
Fields can have default values configured. Default values are inserted into the attribute form when digitizing a new feature. They are visible to the user and can be modified as long as the field is editable. They can be based on the geometry or expression variables.
In QField, there are some additional variables available regarding the current positioning information.
- position_coordinate (Geometry in WGS84!) : Lon, Lat, Altitude as delivered by the sensor. Is also available when the crosshair is not snapped to the sensor.
- position_timestamp (DateTime) : Timestamp of the position information
- position_direction (float) : Direction in degrees from true north.
- position_ground_speed (float) : Groundspeed in meters / second.
- position_magnetic_variation (float) : 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 (float) : The horizontal accuracy of the coordinate (in meters).
- position_vertical_accuracy (float) : The vertical accuracy of the coordinate (in meters).
- position_vertical_speed (float) : The value of the vertical speed in meters per second.
Common use cases
Insert positioning information as variable:
Insert the current date and time:
Insert the length of the digitized line:
Configure global variables on the device and insert them.
If you want to assign a region code based on the location where a new feature is inserted, you can do so by using an aggregate expression:
aggregate( layer:='regions', aggregate:='max', expression:="code", filter:=intersects( $geometry, geometry( @parent ) ) )
The editable flag of fields is respected.
Remember last values
QField offers a much more fine-grained control over the last used values and ignores the QGIS setting.
While digitizing new features, new points can be snapped to existing geometries.
It is possible to snap new points
- only to nodes of existing geomtries
- only to segments of existing geomtries
- to nodes and segments of existing geomtries
Snapping to layers
It is also possible to only snap to one or a few layers.
The snapping tolerance can be specified in map units or pixels.
In almost any case, the units should be set to pixels. We made good experiences with a tolerance value of 20.
GPS devices are capable of measuring the altitude next to the current 2D position on the earth surface. This information can be saved