Obecné nástroje¶

Layers Panel¶

The layers Panel lists all the layers in the project and helps you manage their visibility. 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.

At the top of the Layers panel, a toolbar allows you to:

• ^{Open the layer styling dock}: toggle the layer styling panel on and off.
• ^{Add new group}
• ^{Manage Visibility}: control visibility of layers and preset layers combination.
• ^{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}: helps you apply an expression to remove from the selected layer tree styles that have no feature satisfying the condition. This can be used for example 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 set.
• ^{Expand All} or ^{Collapse All} layers and groups in the layers panel.
• and ^{Remove Layer/Group} currently selected.

Layer Toolbar in Layers Panel

Overview of the context menu of the Layers panel¶

At the bottom of the toolbar, the main component of the Layers panel is the frame listing vector or raster layers added to the project and, those layers can be organized in groups. Depending on the item selected in the panel, a right-click shows a dedicated set of options presented below.

Option	Vector Layer	Raster Layer	Group
Zoom to Layer/Group
Show in Overview
Zoom to Native Resolution (100%)
Stretch Using Current Extent
Remove
Duplicate
Set Layer Scale Visibility
Zoom to Visible Scale
Set Layer/Group CRS
Set Project CRS from Layer
Styles ‣
Copy Style
Paste Style
Open Attribute Table
Toggle Editing
Current Edits ‣	(in Edit mode)
Save As...
Save As Layer Definition File...
Filter...
Show Feature Count
Properties
Move to Top-level
Rename
Group Selected
Set Group WMS Data
Mutually Exclusive Group
Add Group

Table: Context menu from Layers Panel items

For GRASS vector layers, ^{Toggle editing} is not available. See section Digitizing and editing a GRASS vector layer for information on editing GRASS vector layers.

Working with the Legend independent layer order¶

There is a panel that allows you to define an independent drawing order for the layers panel. You can activate it in the menu Settings ‣ Panels ‣ Layer Order Panel. This feature allows you to, for instance, order your layers in order of importance, but still display them in the correct order (see figure_layer_order; you can notice that the airports features are displayed over the alaska polygon despite their layers placement in the Layers panel). Unchecking the Control rendering order box underneath the list of layers will cause a revert to default behavior.

Define a legend independent layer order

Layer Styling Panel¶

This panel is somehow a shortcut to some of the features of the layer properties dialog. It indeed offers you a quick and handy way to define the rendering and the behavior of a layer, and to visualize its effects without opening the layer properties dialog.

Besides avoiding you dealing with the modal and blocking dialog of the layer properties, it also avoids you cluttering the screen with features dialogs given that it embeds most of them (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 its symbology, transparency, and histogram in case of raster layer. These options are the same available in Raster Properties Dialog
• set its symbology, and labels. These options are the same available in The Vector Properties Dialog
• manage the associated style(s) as described in Managing Custom Styles
• follow the whole history of changes you applied to the layer style in the current project; you can therefore cancel or restore to any state by selecting it in the list and hit [Apply] button.

Another powerful feature of this panel is the Live update checkbox. Tick it and your changes are automatically rendered in the map canvas as you go on. You no longer need to hit the [Apply] button.

Defining a layer symbology from the layer styling panel

Statistical Summary Panel¶

This panel can show some statistics on a specific vector layers. The panel allows users to choose:

• the vector layer;
• the column or the expression;
• filter statistics to selected features;
• refresh the informations;
• the statistics information to display with the bottom right button.

Statistic information available are (depending on the field’s type):

Statistics	String	Integer	Float	Date
Count
Count Distinct Value
Count Missing value
Sum
Mean
Standard Deviation
Standard Deviation on Sample
Minimal value
Maximal value
Range
Minority
Majority
Variety
First Quartile
Third Quartile
Inter Quartile Range
Minimum Length
Maximum Length

Table: Statistics available for each field type

Show statistics on a field

QGIS Overview Panel¶

In QGIS, you can use an overview panel that provides a full extent view of layers added to it. Within the view is a rectangle showing the current map extent. This allows you to quickly determine which area of the map you are currently viewing. Note that labels are not rendered to the map overview even if the layers in the map overview have been set up for labelling. If you click and drag the red rectangle in the overview that shows your current extent, the main map view will update accordingly.

Log Messages Panel¶

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.

Undo/Redo Panel¶

For each layer being edited, this panel shows the list of actions done, allowing to quickly undo a set of actions by simply selecting the action listed above. More details at Undo and Redo edits.

Vykreslování v závislosti na měřítku¶

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 General tab, tick the Scale dependent visibility checkbox and enter the Minimum (exclusive) and Maximum (inclusive) scale values.

You can also activate the 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.

The ^{Set to current canvas scale} button helps you use the current map canvas scale as boundary of the range visibility.

Kontrolování vykreslení mapy¶

Vykreslování mapy může být ovládáno různými způsoby, které jsou popsány níže.

Managing Custom Styles¶

When a vector layer is added to map canvas, QGIS uses by default a random symbol/color to render its features. You can however set a default symbol in Project ‣ Project Properties ‣ Default styles that will be applied to each newly added layer according to its geometry type.

But, most of the time, you’d prefer to have a custom and more complex style that can be applied automatically or manually (with less efforts) to the layers. You can achieve this goal using the Style combobox at the bottom of the Layer Properties dialog. This combobox provides you with functions to create, load and manage styles.

A style stores any information set in the layer properties dialog to render or interact with the features (including symbology, labeling, action, diagram... settings) for vector layer, or the pixels (band or color rendering, transparency, pyramids, histogram ...) for raster.

Vector layer style combobox options

By default, the style applied to a loaded layer is named default. Once you have got the ideal and appropriate rendering for your layer, you can save it by clicking the Style combobox and choose:

• Rename Current: The active style gets renamed and updated with the current options
• Add: A new style is created using the current options. By default, it will be saved in the QGIS project file. See below to save the style in another file or a database
• Remove: delete unwanted style, in case you have more than one style defined for the layer.

At the bottom of the Style drop-down list, you see the styles set for the layer and the active one is checked.

Note that each time you validate the layer properties dialog, the active style is updated with the changes you’ve done.

You can create as many styles as you wish for a layer but only one can be active at a time. Combined to layer visibility preset, this offers a quick and powerful way to manage complex projects with few layers (no need to duplicate any layer in the map legend).

Storing Style in a File or a Database¶

While created styles from the Style combobox are by default saved inside the project and can be copied and pasted from layer to layer in the project, it’s also possible to save them outside the project so that they can be loaded in another project.

Save in database¶

Vector layer style can also be stored in a database if the layer datasource is a database provider. Supported formats are PostGIS, GeoPackage, SpatiaLite, MSSQL and Oracle. The layer style is saved inside a table (named layer_styles) of the database. Click on Save Style ‣ Save in database item then fill in the dialog to define a style name, add a description, a .ui file if applicable and check if the style should be the default style.

You can save several styles for a single table in the database. However each table can have only one default style. Default style can be saved in the layer database or in the QGIS local database, a SQLite database in the ~/.qgis2/ directory (where QGIS stores its local settings).

Save Style in database Dialog

Tip

Sharing style files between databases

You can only save your style in a database if the layer comes from such a database. You can’t mix databases (layer in Oracle and style in MSSQL for instance). Use instead a plain text file if you want the style to be shared among databases.

Poznámka

You may encounter issues to restore the layer_styles table from a PostgreSQL database backup. Follow QGIS layer_style table and database backup to fix that.

With the mouse wheel¶

You can press the mouse wheel to pan inside of the main window (on macOS, you may need to hold 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.

With the arrow keys¶

Panning the map is possible with the arrow keys. Place the mouse cursor inside the map area, and click on the right arrow key to pan east, left arrow key to pan west, up arrow key to pan north, and down arrow key to pan south.

You can also use the space bar to temporarily cause mouse movements 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 enabled for the map tools which are not selection tools (since they use Shift for adding to selection) nor edit tools.

General information¶

QGIS provides four means of measuring geometries:

• the interactive measurement tools ,
• measuring in the ^{Field Calculator},
• derived measures in the Identify Features tool,
• and a vector analysis tool: Vector ‣ Geometry Tools ‣ Export/Add Geometry Columns

Measuring works within projected coordinate systems (e.g., UTM) and unprojected data. The first three measuring tools behave equally to global project settings:

• If “on the fly” CRS transformation (see Define On The Fly (OTF) CRS Transformation) is enabled, the default measurement metric is - different from most other GIS - ellipsoidal, using the ellipsoid defined in File ‣ Project properties ‣ General. 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” (File ‣ Project properties ‣ CRS). However, with a geographic (= unprojected) CRS defined for the data and project, area and distance measurement will be ellipsoidal.
• If “on the fly” CRS transformation is disabled, the measurement metric is planimetric when the project coordinate system is projected and ellipsoidal when the project coordinate system is unprojected / geographic.

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: Vector ‣ Geometry Tools ‣ Export/Add Geometry Columns. Here, measurement is by default planimetric except if you choose the ellipsoidal measure.

Measure length, areas and angles interactive¶

Click the icon in the Attribute toolbar to begin measurements. The downward arrow near the icon helps you switch to the convenient tool to measure length, area or angle. The default unit used in the dialog is the one set in Project ‣ Project Properties ‣ General menu.

All measuring modules use the snapping settings from the digitizing module (see section Nastavení přichytávací tolerance a vyhledání poloměru). 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}: QGIS 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 your right mouse button.

Note that you can use the drop-down list near the total to interactively change the measurement units while measuring. This unit is kept for the widget until a new or another project is opened.

The Info section in the dialog explains how calculations are made according to CRS settings available.

Measure Distance

^{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.

Measure Area

^{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 measure is displayed in a pop-up dialog.

Measure Angle

Selecting manually in the map canvas¶

To select one or several features with the mouse, you can use one of the following tools:

• ^{Select Features by area or single click}
• ^{Select Features by Polygon}
• ^{Select Features by Freehand}
• ^{Select Features by Radius}

While using the Select Feature(s) tool, holding Shift or Ctrl toggles whether feature is selected (ie either adds to the current selection or remove from it).

For the other tools, different behaviors can be performed holding:

• 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 to Shift or Ctrl keys, you can add or substract features to/from the current selection.

Automatic selection¶

The other selection tools, also available from the Attribute table, perform a selection based on 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 attribute table, it will be selected in map canvas also):

• ^{Select By Expression...} allows user to select features using expression dialog.
• ^{Select Features By Value...} or press F3
• ^{Deselect Features from All Layers} or press Ctrl+Shift+A to deselect all selected features in all layers.
• ^{Select All Features} or press Ctrl+A to select all features in the current layer.
• ^{Invert Feature Selection} to invert the selection in the current layer.

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, you open the Fields and Values menu and choose the field that you want to query. Double-click the field ‘TYPE_2’ and also click [Load all unique values] in the right panel. From the list, choose and double-click ‘Borough’. In the Expression field, then you’d write the following query:

"TYPE_2"  =  'Borough'

From the expression builder dialog, you can also use the Function list ‣ Recent (Selection) to make a selection that you used before. The dialog remembers the last 20 used expressions. See Výrazy chapter for more information and some example.

Select Features By Value¶

This selection tool opens the layer’s feature form allowing the user to choose, for each field, which value to look for, if the search should be case sensitive, and the operation that should be used.

Filter/Select features using form dialog

Alongside each field, there is a drop-down list with the operation options to control the search behaviour. The common options are:

• Exclude Field - The field will not be used for searching
• Equal to (=)
• Not equal to
• Is missing (null)
• Is not missing (not null)

For numeric and datetime fields, the additional options are:

• Greater than (>)
• Less than (<)
• Greater than or equal to (>=)
• Less than or equal to (<=)
• Between (inclusive)
• Is not between (inclusive)

For text fields, the additional options are:

• Contains
• Does not contain

For the text options above, it is also possible to use the Case sensitive option.

After setting all search options, you can use the Select features button to select the matching features. The drop-down options are:

• Select features
• Add to current selection
• Filter current selection
• Remove from current current selection

You can also clean all search options using the Reset form button.

Using the Identify Features tool¶

QGIS offers two ways to identify features with the ^{Identify Features} tool:

• left click will identify features according to the mode set in the Identify Results panel
• right click will fetch all the snapped features from all the visible layers. This will open a context menu, allowing the user to choose more precisely the features to identify.

If you click on feature(s), the Identify Results dialog will list information about the clicked feature(s). The default view is a tree view where 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 Layer Properties ‣ Display. Then follows all the other information about the feature.

Feature informations¶

The Identify Results dialog can be customized to display custom fields, but by default it will display three kinds of information:

• 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 form for 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. This includes:
  • general information about the feature and its geometry: feature id, length or perimeter and area in map units depending on its geometry, the count of spatial parts and the number of the clicked part in case of multi-geometry, the count of vertices in the feature and the number of the closest one to the point clicked
  • coordinates information: the X and Y (and Z/M if available) coordinate values of the clicked point, the feature closest vertex and its first and last vertices. In case you click on a curved line using the info tool, QGIS will also display the radius of that section in the panel result.
• Data attributes: This is the list of attribute fields and values for the feature that has been clicked.

Identify Results dialog

The Identify Results dialog¶

At the top of the window, you have seven icons:

• ^{Expand tree}
• ^{Collapse tree}
• ^{Default behavior} to define whether next identified features information should be collapsed or expanded
• ^{View the feature form}
• ^{Clear Results}
• ^{Copy selected feature to clipboard}
• ^{Print selected HTML response}

At the bottom of the window, you have the Mode and View comboboxes. With the Mode combobox you can define from which layers features should be identified:

• Current layer : only features from the selected layer are identified. The layer may not be visible in the canvas.
• Top down, stop at first: for only features from the upper visible layer.
• Top down: for all features from the visible layers. The results are shown in the panel.
• and Layer selection: opens a context menu where the user selects the layer to identify features from. Operates like 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.

The identify tool allows you to Auto open a form. If checked, each time a single feature is identified QGIS will open a form showing its attributes. This is a handy way to quickly edit a feature’s attributes.

Další funkce lze nalézt v kontextovém menu identifikovaného prvku. Například, z kontextového menu můžete:

• Zobrazit tvar prvku

• Přiblížit na prvek

• Kopírovat prvek: zkopírovat všechnu geometrii a atributy prvku

• Toggle feature selection: Adds identified feature to selection

• Kopírovat hodnotu atributu: zkopírovat pouze hodnotu atributu, na který kliknete

• Copy feature attributes: Copy the attributes of the feature

• Vymazat výsledek: odstranit výsledky v okně

• Vymazat zvýrazněné: odstranit z mapy zvýraznění prvků

• Zvýraznit všechny

• Zvýraznit vrstvu

• Aktivovat vrstvu: zvolit vrstvu, aby byla aktivní

• Vlastnosti vrstvy: otevřít okno s vlastnostmi vrstvy

• Rozbalit vše

• Sbalit vše

Html annotations¶

The ^{Html Annotation} tools in the attribute toolbar provides the possibility to place the content of an html file in a balloon on the QGIS map canvas. Using the Html Annotation tool, click into the map canvas and add the path to the html file into the dialog.

SVG annotations¶

The ^{SVG Annotation} tool in the attribute toolbar provides the possibility to place an SVG symbol in a balloon on the QGIS map canvas. Using the SVG Annotation tool, click into the map canvas and add the path to the SVG file into the dialog.

Form annotations¶

Additionally, you can also create your own annotation forms. The ^{Form Annotation} tool is useful to display attributes of a vector layer in a customized Qt Designer form (see figure_custom_annotation). This is similar to the designer forms for the Identify features tool, but displayed in an annotation item. Also see this video https://youtu.be/0pDBuSbQ02o?t=2m25s from Tim Sutton for more information.

Customized qt designer annotation form

Tvoření záložek¶

Abyste vytvořili záložku:

1. Přibližte se nebo posuňte na oblast zájmu.

2. Select the menu option View ‣ New Bookmark or press Ctrl-B. The Spatial Bookmark panel opens with the newly created bookmark.

3. Zadejte popisný název záložky (až 255 znaků).

4. Check the In Project box if you wish to save the bookmark in the project file.
5. Press Enter to add the bookmark or click elsewhere.

Můžete mít více záložek se stejným názvem.

Práce se záložkami¶

To use or manage bookmarks, select the menu option View ‣ Show Bookmarks. The Spatial Bookmarks panel allows you to:

• 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 pull down menu in the Spatial Bookmarks dialog. All the bookmarks are transferred.

Mřížka¶

^Mřížka vám umožňuje přidat do mapového okna souřadnicovou síť a její popisky.

Dialog mřížky

1. Select from menu View ‣ Decorations ‣ Grid. The dialog starts (see figure_decorations_grid).
2. Activate the Enable grid checkbox and set grid definitions according to the layers loaded in the map canvas.
3. Activate the Draw annotations checkbox and set annotation definitions according to the layers loaded in the map canvas.
4. Click [Apply] to verify that it looks as expected or [OK] if you’re satisfied.

Značka copyrightu¶

^{Copyright label} adds a copyright label using the text you prefer to the map.

Dialog dekorace popisku s copyrightem

1. Select from menu View ‣ Decorations ‣ Copyright Label. The dialog starts (see figure_decorations_copyright).
2. Make sure the Enable Copyright Label checkbox is checked.
3. Enter the text you want to place on the map. You can use HTML as shown in the example.
4. Choose the placement of the label from the Placement combo box.
5. You can refine the placement of the item by setting a Horizontal and/or Vertical Marging from (Canvas) Edge. These values can be a distance in Millimeter or Pixels or set as Percentage of the width or height of the map canvas.
6. You can change the color to apply.
7. 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 lower right-hand corner of the map canvas.

Směrová růžice¶

^{North Arrow} places a simple north arrow on the map canvas. Currently, there is only one style available. You can adjust the angle of the arrow or let QGIS set the direction automatically. If you choose to let QGIS determine the direction, it makes its best guess as to how the arrow should be oriented. For placement of the arrow, you have four options, corresponding to the four corners of the map canvas. You can refine the placement of the arrow by setting a Horizontal and/or Vertical Marging from (Canvas) Edge. These values can be a distance in Millimeter or Pixels or set as Percentage of the width or height of the map canvas.

The North Arrow Dialog

Měřítko¶

^{Scale Bar} adds a simple scale bar to the map canvas. You can control the style and placement, as well as the labelling of the bar.

Dialog měřítka

QGIS only supports displaying the scale in the same units as your map frame. So if the units of your layers are in 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.

Přidání měřítka

1. Select from menu View ‣ Decorations ‣ Scale Bar. The dialog starts (see figure_decorations_scale).
2. Make sure the Enable scale bar checkbox is checked.
3. Choose the style from the Scale bar style combo box.
4. Select the color for the bar Color of bar or use the default black color.
5. Set the Size of bar .
6. Optionally, check Automatically snap to round number on resize to display values easy-to-read.
7. Choose the placement from the Placement combo box.
8. You can refine the placement of the item by setting a Horizontal and/or Vertical Marging from (Canvas) Edge. These values can be a distance in Millimeter or Pixels or set as Percentage of the width or height of the map canvas.
9. Click [Apply] to verify that it looks as expected or [OK] if you’re satisfied.