Whenever you need help on a specific topic, you can access the corresponding page in the current User Manual via the Help button available in most dialogs — please note that third-party plugins can point to dedicated web pages.
By default, QGIS provides many panels to work with. Some of these panels are described below while others may be found in different parts of the document. A complete list of default panels provided by QGIS is available via the Panels.menu and mentioned at
The Layers panel (also called the
map legend) lists all
the layers in the project and helps you
manage their visibility. You can show or hide it by pressing Ctrl+1.
A layer can be selected and dragged up or down in the
legend to change the Z-ordering. Z-ordering means that layers listed nearer the
top of the legend are drawn over layers listed lower down in the legend.
The Z-ordering behavior can be overridden by the Layer Order panel.
At the top of the Layers panel, a toolbar allows you to:
Filter Legend by Map Content: only the layers that are set visible and whose features intersect the current map canvas have their style rendered in the layers panel. Otherwise, a generic NULL symbol is applied to the layer. Based on the layer symbology, this is a convenient way to identify which kind of features from which layers cover your area of interest.
Filter Legend by Expression: apply an expression to remove styles from the selected layer tree that have no feature satisfying the condition. This can be used to highlight features that are within a given area/feature of another layer. From the drop-down list, you can edit and clear the expression currently applied.
Tools to manage the layers panel are also available for map and legend items in print layouts
Beyond the simple control of layer visibility, the Manage Map Themes menu allows you to configure Map Themes in the legend and switch from one map theme to another. A map theme is a snapshot of the current map legend that records:
the layers set as visible in the Layers panel
and for each visible layer:
To create a map theme:
Check a layer you want to show
Configure the layer properties (symbology, diagram, labels…) as usual
Expand the Add… to store the settings as a new style embedded in the projectmenu at the bottom and click on
A map theme does not remember the current details of the properties: only a reference to the style name is saved, so whenever you apply modifications to the layer while this style is enabled (eg change the symbology rendering), the map theme is updated with new information.
Repeat the previous steps as necessary for the other layers
If applicable, expand or collapse groups or visible layer nodes in the Layers panel
Enter the map theme’s name and click OK
You can create as many map themes as you need: whenever the current combination in the map legend (visible layers, their active style, the map legend nodes) does not match any existing map theme contents as defined above, click on Add Theme… to create a new map theme, or use to update a map theme. Use the button to delete the active theme.
Map themes are helpful to switch quickly between different preconfigured combinations: select a map theme in the list to restore its combination. All configured themes are also accessible in the print layout, allowing you to create different map items based on specific themes and independent of the current main canvas rendering (see Map item layers).
Layers in the legend window can be organized into groups. There are two ways to do this:
Select some layers, right-click in the legend window and choose Group Selected. The selected layers will automatically be placed in a new group.
To move a layer out of a group, drag it out, or right-click on it and choose Move Out of Group: the layer is moved from the group and placed above it. Groups can also be nested inside other groups. If a layer is placed in a nested group, Move Out of Group will move the layer out of all nested groups.
To move a group or layer to the top of the layer panel, either drag it to the top, or choose Move to Top. If you use this option on a layer nested in a group, the layer is moved to the top in its current group.
The checkbox for a group will show or hide all the layers in the group with one click.
Enabling the Mutually Exclusive Group option means you can make a group have only one layer visible at the same time. Whenever a layer within the group is set visible the others will be toggled not visible.
It is possible to select more than one layer or group at the same time by holding down the Ctrl key while clicking additional layers. You can then move all selected layers to a new group at the same time.
You may also delete more than one layer or group at once by selecting several items with the Ctrl key and then pressing Ctrl+D: all selected layers or groups will be removed from the layers list.
In some circumstances, icons appears next to the layer or group in the Layers panel to give more information about the layer/group. These symbols are:
to indicate a filter applied to the layer. Hover over the icon to see the filter expression and double-click to update the setting
to identify an embedded group or layer and the path to their original project file
to remind you that the layer is a temporary scratch layer and its content will be discarded when you close this project. To avoid data loss and make the layer permanent, click the icon to store the layer in any of the OGR vector formats supported by QGIS.
From the Layers panel, you have shortcuts to change the layer rendering quickly and easily. Right-click on a vector layer and selectin the list in order to:
see the styles currently applied to the layer. If you defined many styles for the layer, you can switch from one to another and your layer rendering will automatically be updated on the map canvas.
copy the current style, and when applicable, paste a copied style from another layer
rename the current style, add a new style (which is actually a copy of the current one) or delete the current style (when multiple styles are available).
The previous options are also available for raster layers.
Whether the features in the vector layer all have the same unique symbol or they are classified (in which case the layer is displayed in a tree structure with each class as a sub-item), the following options are available at layer level or class level:
Edit Symbol… to open the The Symbol Selector dialog to change any properties of the layer or feature symbol (symbol, size, color…). Double-clicking on a feature also opens the Symbol Selector dialog.
Color Selector with a Color Wheel from which you can click a color to update the symbol fill color automatically. For convenience, Recent colors are available at the bottom of the color wheel.
Quickly share a layer style
From the context menu, copy the style of a layer and paste it to a group or a selection of layers: the style is applied to all the layers that are of the same type (vector/raster) as the original layer and, for vector layers, have the same geometry type (point, line or polygon).
The Layer Styling panel (also enabled with Ctrl+3) is a shortcut to some of the functionalities of the Layer Properties dialog. It provides a quick and easy way to define the rendering and the behavior of a layer, and to visualize its effects without having to open the layer properties dialog.
In addition to avoiding the blocking (or «modal») layer properties dialog, the layer styling panel also avoids cluttering the screen with dialogs, and contains most style functions (color selector, effects properties, rule edit, label substitution…): e.g., clicking color buttons inside the layer style panel causes the color selector dialog to be opened inside the layer style panel itself rather than as a separate dialog.
From a drop-down list of current layers in the layer panel, select an item and:
Set raster layer Symbology, Transparency, and Histogram properties. These options are the same as those in the Свойства растра.
Set vector layer Symbology, 3D View and Labels properties. These options are the same as those in the Свойства векторного слоя.
Manage the associated style(s) in the Style Manager (more details at Managing Custom Styles).
Add custom tabs to the Layer Styling panel
Using PyQGIS, you can set new tabs to manage layer properties in the Layer Styling Panel. See https://nathanw.net/2016/06/29/qgis-style-dock-part-2-plugin-panels/ for an example.
By default, layers shown on the QGIS map canvas are drawn following their order in the Layers panel: the higher a layer is in the panel, the higher (hence, more visible) it’ll be in the map view.
You can define a drawing order for the layers independent of the order in the
layers panel with the Layer Order panel enabled
in menu or with Ctrl+9.
Check Control rendering order underneath
the list of layers and reorganize the layers in the panel as you want. This
order becomes the one applied to the map canvas.
For example, in figure_layer_order, you can see that the
features are displayed over the
alaska polygon despite those layers“
respective placement in the Layers panel.
The Overview panel (Ctrl+8) displays a map with a full extent view of some of the layers. The Overview map is filled with layers using the Show in Overview option from the menu or in the layer contextual menu. Within the view, a red rectangle shows the current map canvas extent, helping you quickly to determine which area of the whole map you are currently viewing. If you click-and-drag the red rectangle in the overview frame, the main map view extent will update accordingly.
Note that labels are not rendered to the map overview even if the layers used in the map overview have been set up for labeling.
When loading or processing some operations, you can track and follow messages that appear in different tabs using the Log Messages Panel. It can be activated using the most right icon in the bottom status bar.
For each layer being edited, the Undo/Redo (Ctrl+5) panel shows the list of actions carried out, allowing you quickly to undo a set of actions by selecting the action listed above. More details at Undo and Redo edits.
The Statistics panel (Ctrl+6) provides summarized information on any vector layer. This panel allows you to select:
the vector layer to compute the statistics on
the column to use, or an expression
the statistics to return using the drop-down button at the bottom-right of the dialog. Depending on the field’s (or expression’s values) type, available statistics are:
Count Distinct Value
Count Missing value
Standard Deviation on Sample
Inter Quartile Range
Table: Statistics available for each field type
The statistical summary can be:
Sometimes, you’d like to keep some layers in different projects, but with the same style. You can either create a default style for these layers or embed them from another project to save time and effort.
Embed layers and groups from an existing project has some advantages over styling:
All types of layers (vector or raster, local or online…) can be added
Fetching groups and layers, you can keep the same tree structure of the «background» layers in your different projects
While the embedded layers are editable, you can’t change their properties such as symbology, labels, forms, default values and actions, ensuring consistency across projects
Modify the items in the original project and changes are propagated to all the other projects
If you want to embed content from other project files into your project, select:
Click the … button to look for a project: you can see the content of the project (see figure_embed_dialog)
The selected layers and groups are embedded in the Layers panel and displayed on the map canvas. An icon is added next to their name for recognition and hovering over displays a tooltip with the original project file path.
Change rendering of an embedded layer
It’s not possible to change the rendering of an embedded layer, unless you make the changes in the original project file. However, right-clicking on a layer and selecting Duplicate creates a layer which is fully-featured and not dependent on the original project. You can then safely remove the linked layer.
By default, QGIS renders all visible layers whenever the map canvas is refreshed. The events that trigger a refresh of the map canvas include:
adding a layer
panning or zooming
resizing the QGIS window
changing the visibility of a layer or layers
QGIS allows you to control the rendering process in a number of ways.
Scale-dependent rendering allows you to specify the minimum and maximum scales at which a layer (raster or vector) will be visible. To set scale-dependent rendering, open the Properties dialog by double-clicking on the layer in the legend. On the Rendering tab, tick Scale dependent visibility and enter the Minimum (exclusive) and Maximum (inclusive) scale values.
You can also activate scale dependent visibility on a layer from the Layers panel. Right-click on the layer and in the context menu, select Set Layer Scale Visibility.
When a layer is not rendered in the map canvas because the map scale is out of its visibility scale range, the layer is greyed in the Layers panel and a new option Zoom to Visible Scale appears in the layer context menu. Select it and the map is zoomed to the layer’s nearest visibility scale.
Map rendering can be controlled in various ways, as described below.
To suspend rendering, click the Render checkbox in the bottom-right corner of the status bar. When Render is not checked, QGIS does not redraw the canvas in response to any of the events described in the section Рендеринг. Examples of when you might want to suspend rendering include:
adding many layers and symbolizing them prior to drawing
adding one or more large layers and setting scale dependency before drawing
adding one or more large layers and zooming to a specific view before drawing
any combination of the above
You can set an option to always load new layers without drawing them. This means the layer will be added to the map, but its visibility checkbox in the legend will be unchecked by default. To set this option, choose menu option Rendering tab. Uncheck By default new layers added to the map should be displayed. Any layer subsequently added to the map will be off (invisible) by default.and click on the
To stop the map drawing, press the Esc key. This will halt the refresh of the map canvas and leave the map partially drawn. It may take a bit of time between pressing Esc for the map drawing to halt.
It is currently not possible to stop rendering — this was disabled in the Qt4 port because of User Interface (UI) problems and crashes.
There are some settings that allow you to improve rendering speed. Open the QGIS options dialog using Rendering tab and select or deselect the following checkboxes:, go to the
The map renders in the background onto a separate image and each Map Update interval, the content from this (off-screen) image will be taken to update the visible screen representation. However, if rendering finishes faster than this duration, it will be shown instantaneously.
With Enable Feature simplification by default for newly added layers, you simplify features“ geometry (fewer nodes) and as a result, they display more quickly. Be aware that this can cause rendering inconsistencies.
QGIS provides tools to zoom and pan to your area of interest.
Apart from using the pan and zoom-in/ zoom-out icons on the toolbar with the mouse, you can also navigate with the mouse wheel, spacebar and arrow keys. A Zoom factor can be set under the menu to define the scale behavior while zooming.
You can press the mouse wheel to pan inside of the main window (on macOS, you may need to hold down the cmd key). You can roll the mouse wheel to zoom in and out on the map; the mouse cursor position will be the center of the zoomed area of interest. Holding down Ctrl while rolling the mouse wheel results in a finer zoom.
Panning the map is possible with the arrow keys. Place the mouse cursor inside the map area, and click on the arrow keys to pan up, down, left and right.
You can also use the space bar to cause mouse movements temporarily to pan the map. The PgUp and PgDown keys on your keyboard will cause the map display to zoom in or out following the zoom factor set. Pressing Ctrl++ or Ctrl+- also performs an immediate zoom in/out on the map canvas.
When certain map tools are active (Identify, Measure…), you can perform a zoom by holding down Shift and dragging a rectangle on the map to zoom to that area. This is not enabled for selection tools (since they use Shift for adding to selection) or edit tools.
Spatial Bookmarks allow you to «bookmark» a geographic location and return to
it later. By default, bookmarks are saved on the computer, meaning that they are available
from any project in the same computer. If you wish to store the bookmark in the project
.qgs) then you can do this by selecting the In Project checkbox.
Для создания закладки:
Масштабируйте или панорамируйте карту до интересующей вас территории.
Select the menu option Spatial Bookmarks panel opens with the newly created bookmark.or press Ctrl+B. The
введите описательное имя для закладки (до 255 символов)
Check the In Project box if you wish to save the bookmark in the project file.
Press Enter to add the bookmark or click elsewhere.
Помните, что можно иметь множество закладок с одинаковыми названиями.
To use or manage bookmarks, select Spatial Bookmarks panel allows you to:or press Ctrl+7. The
Zoom to a Bookmark: select the desired bookmark and then click Zoom To Bookmark. You can also zoom to a bookmark by double-clicking on it.
Delete a Bookmark: select the bookmark and click Delete Bookmark. Confirm your choice.
Import or Export a bookmark: To share or transfer your bookmarks between computers you can use the Import/Export Bookmarks drop-down menu to export all bookmarks to an
.xmlfile or import bookmarks from such a file.
You can also zoom to saved bookmarks by typing the bookmark name in the locator.
Decorations include Grid, Copyright Label, North Arrow, Scale Bar and Layout Extents. They are used to „decorate“ the map by adding cartographic elements.
Selectto open the dialog
Enter the text you want to place on the map. You can include expressions (using the Insert an Expression button).
Refine the placement of the item by setting a horizontal and/or vertical Margin from Edge. These values can be in Millimeters or Pixels or set as a Percentage of the width or height of the map canvas.
You can change the color to apply
Click Apply to verify that it looks as expected or OK if you’re satisfied.
In the example above, which is the default, QGIS places a copyright symbol followed by the date in the bottom-right corner of the map canvas.
To add a north arrow:
Selectto open the dialog.
Optionally change the color and size, or choose a custom SVG.
Optionally change the angle or choose Automatic to let QGIS determine the direction
Optionally choose the placement from the Placement combo box
Optionally refine the placement of the arrow by setting a horizontal and/or vertical Margin from (Canvas) Edge. These values can be in Millimeters or Pixels or set as a Percentage of the width or height of the map canvas.
Click Apply to verify that it looks as expected and OK if you’re satisfied.
QGIS only supports displaying the scale in the same units as your map frame. So, if the units of your project’s CRS are meters, you can’t create a scale bar in feet. Likewise, if you are using decimal degrees, you can’t create a scale bar to display distance in meters.
Для добавления масштабной линейки:
Selectto open the dialog
Select the Color of bar by choosing a fill color (default: black) and an outline color (default: white). The scale bar fill and outline can be made opaque by clicking on the down arrow to the right of the color input.
You can refine the placement of the item by setting a horizontal and/or vertical Margin from (Canvas) Edge. These values can be in Millimeters or Pixels or set as a Percentage of the width or height of the map canvas.
Click Apply to verify that it looks as expected or OK if you’re satisfied.
Layout Extents adds the extents of map item(s) in print layout(s) to the canvas. When enabled, the extents of all map items within all print layouts are shown using a lightly dotted border labeled with the name of the print layout and map item. You can control the style and labeling of the displayed layout extents. This decoration is useful when you are tweaking the positioning of map elements such as labels, and need to know the actual visible region of print layouts.
To add layout extent(s):
Selectto open the dialog
Optionally change the symbol and labeling of the extents
Click Apply to verify that it looks as expected and OK if you’re satisfied
When you save a QGIS project file, any changes you have made to Grid, North Arrow, Scale Bar, Copyright and Layout Extents will be saved in the project and restored the next time you load the project.
Annotations are information added to the map canvas and shown within a balloon. This information can be of different types and annotations are added using the corresponding tools in the Attributes Toolbar:
Form Annotation: useful to display attributes of a vector layer in a customized
uifile (see figure_custom_annotation). This is similar to the custom attribute forms, but displayed in an annotation item. Also see this video https://youtu.be/0pDBuSbQ02o?t=2m25s from Tim Sutton for more information.
To add an annotation, select the corresponding tool and click on the map canvas. An empty balloon is added. Double-click on it and a dialog opens with various options. This dialog is almost the same for all the annotation types:
At the top, a file selector to fill with the path to an
uifile depending on the type of annotation. For text annotation, you can enter your message in a text box and set its rendering with the normal font tools.
Linked layer: associates the annotation with a map layer, making it visible only when that layer is visible.
Map marker: using QGIS symbols, sets the symbol to display at the balloon anchor position (shown only when Fixed map position is checked).
Frame style: sets the frame background color, transparency, stroke color or width of the balloon using QGIS symbols.
Contents margins: sets interior margins of the annotation frame.
Annotations can be selected when an annotation tool is enabled. They can then be moved by map position (by dragging the map marker) or by moving only the balloon. The Move Annotation tool also allows you to move the balloon on the map canvas.
To delete an annotation, select it and either press the Del or Backspace button, or double-click it and press the Delete button in the properties dialog.
If you press Ctrl+T while an Annotation tool (move annotation, text annotation, form annotation) is active, the visibility states of the items are inverted.
Layout the map with annotations
You can print or export annotations with your map to various formats using:
map canvas export tools available in themenu
print layout, in which case you need to check Draw map canvas items in the corresponding map item properties
QGIS provides four means of measuring geometries:
derived measurements in the Identifying Features tool
the vector analysis tool:
Measuring works within projected coordinate systems (e.g., UTM) and unprojected data. The first three measuring tools behave equally to global project settings:
Unlike most other GIS, the default measurement metric is ellipsoidal, using the ellipsoid defined in. This is true both when geographic and projected coordinate systems are defined for the project.
If you want to calculate the projected/planimetric area or distance using cartesian maths, the measurement ellipsoid has to be set to «None/Planimetric» (). However, with a geographic (ie unprojected) CRS defined for the data and project, area and distance measurement will be ellipsoidal.
However, neither the identify tool nor the field calculator will transform your data to the project CRS before measuring. If you want to achieve this, you have to use the vector analysis tool:. Here, measurement is planimetric, unless you choose the ellipsoidal measurement.
Configuring the measure tool
While measuring length or area, clicking the Configuration button at the bottom of the widget opens the menu, where you can select the rubberband color, the precision of the measurements and the unit behavior. You can also choose your preferred measurement or angle units, but keep in mind that those values are overridden in the current project by the selection made in the menu, and by the selection made in the measurement widget.
All measuring modules use the snapping settings from the digitizing module (see section Настройка порога прилипания и радиуса поиска). So, if you want to measure exactly along a line feature, or around a polygon feature, first set its layer snapping tolerance. Now, when using the measuring tools, each mouse click (within the tolerance setting) will snap to that layer.
By default, Measure Line measures real distances between given points according to a defined ellipsoid. The tool then allows you to click points on the map. Each segment length, as well as the total, shows up in the measure window. To stop measuring, click the right mouse button.
Note that you can use the drop-down list near the total to change the measurement units interactively while working with the measure tool („Meters“, „Kilometers“, „Feet“, „Yards“, „Miles“, „Nautical miles“, „Centimeters“, „Millimeters“, „Degrees“, „Map units“). This unit is retained for the widget until a new project is created or another project is opened.
The Info section in the dialog explains how calculations are made according to the CRS settings available.
Measure Area: Areas can also be measured. In the measure window, the accumulated area size appears. Right-click to stop drawing. The Info section is also available as well as the ability to switch between different area units („Square meters“, „Square kilometers“, „Square feet“, „Square yards“, „Square miles“, „Hectares“, „Acres“, „Square centimeters“, „Square millimeters“, „Square nautical miles“, „Square degrees“, „Map units“).
Measure Angle: You can also measure angles. The cursor becomes cross-shaped. Click to draw the first segment of the angle you wish to measure, then move the cursor to draw the desired angle. The measurement is displayed in a pop-up dialog.
QGIS provides several tools to select features on the map canvas. Selection tools are available in the Attributes toolbar.menu or in the
Selection tools work with the currently active layer.
To select one or more features with the mouse, you can use one of the following tools:
Use the Select Features by Polygon tool to use an existing polygon to select overlapping features. Right-click in the polygon and choose it from the context menu that shows a list of all the polygons that contain the clicked point. All the overlapping features from the active layer are selected.
For the other tools, different behaviors can be performed by holding down:
Shift: add features to the current selection
Ctrl: substract features from the current selection
Ctrl+Shift: intersect with current selection, ie only keep overlapping features from the current selection
Alt: select features that are totally within the selection shape. Combined with Shift or Ctrl keys, you can add or substract features to/from the current selection.
The other selection tools, also available from the Attribute table, perform a selection based on a feature’s attribute or its selection state (note that attribute table and map canvas show the same information, so if you select one feature in the attribute table, it will be selected on the map canvas too):
For example, if you want to find regions that are boroughs from
regions.shp of the QGIS sample data, you can use the
Select features using an Expression icon. Then, expand the
Fields and Values group and choose the field that you want to query.
Double-click the field „TYPE_2“ and also click All Unique in the
panel that shows up. From the list, choose and double-click „Borough“. In the
Expression field, write the following query:
"TYPE_2" = 'Borough'
From the expression builder dialog, you can also use Expressions for more information and examples.to make a selection that you have used before. The dialog remembers the last 20 expressions used. See
Save your selection into a new file
Users can save selected features into a New Temporary Scratch Layer or a New Vector Layer usingand in the desired format.
This selection tool opens the layer’s feature form allowing the user to choose which value to look for for each field, whether the search should be case-sensitive, and the operation that should be used. The tool has also autocompletes, automatically filling the search box with existing values.
Alongside each field, there is a drop-down list with options to control the search behaviour:
Field search option
Exclude Field from the search
Equal to (=)
Not equal to (≠)
Greater than (>)
Less than (<)
Greater than or equal to (≥)
Less than or equal to (≤)
Not between (inclusive)
Does not contain
Is missing (null)
Is not missing (not null)
After setting all search options, click Select features to select the matching features. The drop-down options are:
Add to current selection
Filter current selection
Remove from current current selection
You can also clear all search options using the Reset form button.
Once the conditions are set, you can also either:
Zoom to features on the map canvas without the need of a preselection
Flash features, highlighting the matching features. This is a handy way to identify a feature without selection or using the Identify tool. Note that the flash does not alter the map canvas extent and would be visible only if the feature is within the bounds of the current map canvas.
The Identify tool allows you to interact with the map canvas and get information on features in a pop-up window. To identify features, use:
right click with Identify Feature(s) as selection mode set in the Identify Results panel fetches all snapped features from all visible layers. This opens a context menu, allowing the user to choose more precisely the features to identify or the action to execute on them.
right click with Identify Features by Polygon as selection mode in the Identify Results panel identifies the features that overlap with the chosen existing polygon, according to the selection mask set in the Identify Results panel
Filter the layers to query with the Identify Features tool
Under Layer Capabilities in , uncheck the Identifiable column next to a layer to avoid it being queried when using the Identify Features tool in a mode other than Current Layer. This is a handy way to return features from only layers that are of interest for you.
If you click on feature(s), the Identify Results dialog will list information about the feature(s) clicked. The default view is a tree view in which the first item is the name of the layer and its children are its identified feature(s). Each feature is described by the name of a field along with its value. This field is the one set in . All the other information about the feature follows.
The Identify Results dialog can be customized to display custom fields, but by default it will display the following information:
The feature display name;
Actions: Actions can be added to the identify feature windows. The action is run by clicking on the action label. By default, only one action is added, namely
View feature formfor editing. You can define more actions in the layer’s properties dialog (see Actions Properties).
Derived: This information is calculated or derived from other information. It includes:
general information about the feature’s geometry:
depending on the geometry type, the cartesian measurements of length, perimeter or area in the layer’s CRS units
depending on the geometry type and if an ellipsoid is set in the project properties dialog for Measurements, the ellipsoidal values of length, perimeter or area using the specified units
the count of geometry parts in the feature and the number of the part clicked
the count of vertices in the feature
coordinate information, using the project properties Coordinates display settings:
Ycoordinate values of the point clicked
the number of the closest vertex to the point clicked
Ycoordinate values of the closest vertex (and
if you click on a curved segment, the radius of that section is also displayed.
Data attributes: This is the list of attribute fields and values for the feature that has been clicked.
Links in the feature’s attributes are clickable from the Identify Results panel and will open in your default web browser.
At the top of the window, you have a handful of tools:
selection mode to use to fetch features to identify:
At the bottom of the window are the Mode and View comboboxes. Mode defines from which layers features should be identified:
Current layer: only features from the selected layer are identified. The layer need not be visible in the canvas.
Top down, stop at first: only features from the upper visible layer.
Top down: all features from the visible layers. The results are shown in the panel.
Layer selection: opens a context menu where the user selects the layer to identify features from, similar to a right-click. Only the chosen features will be shown in the result panel.
The View can be set as Tree, Table or Graph. „Table“ and „Graph“ views can only be set for raster layers.
Other functions can be found in the context menu of the identified item. For example, from the context menu you can:
View the feature form
Увеличить до объекта
Copy feature: Copy all feature geometry and attributes
Toggle feature selection: Add identified feature to selection
Copy attribute value: Copy only the value of the attribute that you click on
Copy feature attributes: Copy the attributes of the feature
Clear result: Remove results in the window
Clear highlights: Remove features highlighted on the map
Подсветить всё в слое
Activate layer: Choose a layer to be activated
Layer properties: Open layer properties window
In QGIS, you can use variables to store useful recurrent values (e.g. the
project’s title, or the user’s full name) that can be used in expressions.
Variables can be defined at the application’s global level, project level,
layer level, layout level, and layout item’s level. Just like CSS
cascading rules, variables can be overwritten - e.g., a project level
variable will overwrite any application global level variables set with
the same name. You can use these variables to build text strings or other
custom expressions using the
@ character before the variable name. For
example in print layout creating a label with this content:
This map was made using QGIS [% @qgis_version %]. The project file for this map is: [% @project_path %]
Will render the label like this:
This map was made using QGIS 3.4.4-Madeira. The project file for this map is: /gis/qgis-user-conference-2019.qgs
Besides the preset read-only variables, you can define your own custom variables for any of the levels mentioned above. You can manage:
global variables from themenu
project variables from the Project Properties dialog (see Свойства проекта)
vector layer variables from the Layer Properties dialog (see Свойства векторного слоя);
layout variables from the Layout panel in the Print layout (see The Layout Panel);
and layout item variables from the Item Properties panel in the Print layout (see Layout Items Common Options).
To differentiate from editable variables, read-only variable names and values are displayed in italic. On the other hand, higher level variables overwritten by lower level ones are strike through.
QGIS has the facility to store/retrieve authentication credentials in a secure manner. Users can securely save credentials into authentication configurations, which are stored in a portable database, can be applied to server or database connections, and are safely referenced by their ID tokens in project or settings files. For more information see Authentication System.
A master password needs to be set up when initializing the authentication system and its portable database.
In QGIS, there are some options you’ll often have to work with. For convenience, QGIS provides you with special widgets that are presented below.
The Select Color dialog will appear whenever you click the icon to choose a color. The features of this dialog depend on the state of the Use native color chooser dialogs parameter checkbox in . When checked, the color dialog used is the native one of the OS on which QGIS is running. Otherwise, the QGIS custom color chooser is used.
The custom color chooser dialog has four different tabs which allow you to select colors by Color ramp, Color wheel, Color swatches or Color picker. With the first two tabs, you can browse to all possible color combinations and apply your choice to the item.
In the Color swatches tab, you can choose from a list of color palettes (see Colors Settings for details). All but the Recent colors palette can be modified with the Add current color and Remove selected color buttons at the bottom of the frame.
The … button next to the palette combobox also offers several options to:
copy, paste, import or export colors
create, import or remove color palettes
add the custom palette to the color selector widget with the Show in Color Buttons item (see figure_color_selector)
Another option is to use the Color picker which allows you to sample a color from under your mouse cursor at any part of the QGIS UI or even from another application: press the space bar while the tab is active, move the mouse over the desired color and click on it or press the space bar again. You can also click the Sample Color button to activate the picker.
Whatever method you use, the selected color is always described through color
HSV (Hue, Saturation, Value) and
RGB (Red, Green, Blue)
values. The color is also identifiable in HTML notation.
Modifying a color is as simple as clicking on the color wheel or ramp or on any of the color parameters sliders. You can adjust such parameters with the spinbox beside or by scrolling the mouse wheel over the corresponding slider. You can also type the color in HTML notation. Finally, there is an Opacity slider to set transparency level.
The dialog also provides a visual comparison between the Old color (applied to object) and the Current one (being selected). Using drag-and-drop or pressing the Add color to swatch button, any of these colors can be saved in a slot for easy access.
Quick color modification
Drag-and-drop a color selector widget onto another one to apply its color.
Click the drop-down arrow to the right of the color button to display a widget for quick color selection. This shortcut provides access to:
a color wheel to pick a color from
an alpha slider to change color opacity
the color palettes previously set to Show in Color Buttons
copy the current color and paste it into another widget
pick a color from anywhere on your computer display
choose a color from the color selector dialog
Color ramps are a practical way to apply a set of colors to one or many features. Their creation is described in the Градиент section. As for the colors, pressing the color ramp button opens the corresponding color ramp type dialog allowing you to change its properties.
The drop-down menu to the right of the button gives quick access to a wider set of color ramps and options:
Invert Color Ramp
a preview of the
catalog: cpt-citycolor ramps flagged as Favorites in the Style Manager dialog
All Color Ramps to access the compatible color ramps database
Create New Color Ramp… of any supported type that could be used in the current widget (note that this color ramp will not be available elsewhere unless you save it in the library)
Edit Color Ramp…, the same as clicking the whole color ramp button
Save Color Ramp…, to save the current color ramp with its customizations in the style library
QGIS offers different options for special rendering effects with these tools that you may previously only know from graphics programs. Blending modes can be applied on layers and features, and also on print layout items:
Normal: This is the standard blend mode, which uses the alpha channel of the top pixel to blend with the pixel beneath it. The colors aren’t mixed.
Lighten: This selects the maximum of each component from the foreground and background pixels. Be aware that the results tend to be jagged and harsh.
Screen: Light pixels from the source are painted over the destination, while dark pixels are not. This mode is most useful for mixing the texture of one item with another item (such as using a hillshade to texture another layer).
Dodge: Brighten and saturate underlying pixels based on the lightness of the top pixel. Brighter top pixels cause the saturation and brightness of the underlying pixels to increase. This works best if the top pixels aren’t too bright. Otherwise the effect is too extreme.
Addition: Adds pixel values of one item to the other. In case of values above the maximum value (in the case of RGB), white is displayed. This mode is suitable for highlighting features.
Darken: Retains the lowest values of each component of the foreground and background pixels. Like lighten, the results tend to be jagged and harsh.
Multiply: Pixel values of the top item are multiplied with the corresponding values for the bottom item. The results are darker.
Burn: Darker colors in the top item cause the underlying items to darken. Burn can be used to tweak and colorize underlying layers.
Overlay: Combines multiply and screen blending modes. Light parts become lighter and dark parts become darker.
Soft light: Very similar to overlay, but instead of using multiply/screen it uses color burn/dodge. This is supposed to emulate shining a soft light onto an image.
Hard light: Hard light is also very similar to the overlay mode. It’s supposed to emulate projecting a very intense light onto an image.
Difference: Subtracts the top pixel from the bottom pixel, or the other way around, in order always to get a positive value. Blending with black produces no change, as the difference with all colors is zero.
Subtract: Subtracts pixel values of one item from the other. In the case of negative values, black is displayed.
Next to many options in the vector layer properties dialog or settings in the print layout, you will find a Data defined override icon. Using expressions based on layer attributes or item settings, prebuilt or custom functions and variables, this tool allows you to set dynamic values for parameters. When enabled, the value returned by this widget is applied to the parameter regardless of its normal value (checkbox, textbox, slider…).
Description… that indicates if the option is enabled, which input is expected, the valid input type and the current definition. Hovering over the widget also pops up this information.
Store data in the project: a button allowing the property to be stored using to the Auxiliary Storage Properties mechanism.
Field type: an entry to select from the layer’s fields that match the valid input type.
An entry to list the Variable available.
Edit… button to create or edit the expression to apply, using the Expression String Builder dialog. To help you correctly fill in the expression, a reminder of the expected output’s format is provided in the dialog.
Paste and Copy buttons.
Clear button to remove the setup.
For numeric and color properties, Assistant… to rescale how the feature data is applied to the property (more details below)
Use right-click to (de)activate the data override
When the Data-defined override button is associated with a numeric or color parameter, it has an Assistant… option that allows you to change how the data is applied to the parameter for each feature. The assistant allows you to:
Define the Input data, ie:
the attribute to represent, using the Field listbox or the Set column expression function (see Expressions)
the range of values to represent: you can manually enter the values or use the Fetch value range from layer button to fill these fields automatically with the minimum and maximum values returned by the chosen attribute or the expression applied to your data
Apply transform curve: by default, output values (see below for setting) are applied to input features following a linear scale. You can override this logic: enable the transform option, click on the graphic to add break point(s) and drag the point(s) to apply a custom distribution.
Define the Output values: the options vary according to the parameter to define. You can globally set:
the minimum and maximum values to apply to the selected property (n case of a color setting, you’ll need to provide a color ramp)
the Scale method of representation which can be Flannery, Exponential, Surface or Radius
the Exponent to use for data scaling
the output value or color to represent features with NULL values
When compatible with the property, a live-update preview is displayed in the right-hand side of the dialog to help you control the value scaling.
The values presented in the varying size assistant above will set the size „Data-defined override“ with:
coalesce(scale_exp(Importance, 1, 20, 2, 10, 0.57), 1)