Editando¶

Tolerância de Atracção¶

Snapping tolerance is the distance QGIS uses to search for the closest vertex and/or segment you are trying to connect to when you set a new vertex or move an existing vertex. If you aren’t within the snapping tolerance, QGIS will leave the vertex where you release the mouse button, instead of snapping it to an existing vertex and/or segment. The snapping tolerance setting affects all tools that work with tolerance.

1. A general, project-wide snapping tolerance can be defined by choosing Settings ‣ Options. On Mac, go to QGIS ‣ Preferences.... On Linux: Edit ‣ Options. In the Digitizing tab, you can select between ‘to vertex’, ‘to segment’ or ‘to vertex and segment’ as default snap mode. You can also define a default snapping tolerance and a search radius for vertex edits. The tolerance can be set either in map units or in pixels. The advantage of choosing pixels is that the snapping tolerance doesn’t have to be changed after zoom operations. In our small digitizing project (working with the Alaska dataset), we define the snapping units in feet. Your results may vary, but something on the order of 300 ft at a scale of 1:10000 should be a reasonable setting.
2. A layer-based snapping tolerance can be defined by choosing Settings ‣ (or File ‣) Snapping options... to enable and adjust snapping mode and tolerance on a layer basis (see figure_edit_1 ).

Note that this layer-based snapping overrides the global snapping option set in the Digitizing tab. So, if you need to edit one layer and snap its vertices to another layer, then enable snapping only on the snap to layer, then decrease the global snapping tolerance to a smaller value. Furthermore, snapping will never occur to a layer that is not checked in the snapping options dialog, regardless of the global snapping tolerance. So be sure to mark the checkbox for those layers that you need to snap to.

Figure Edit 1:

Edit snapping options on a layer basis

Raio de pesquisa¶

Search radius is the distance QGIS uses to search for the closest vertex you are trying to move when you click on the map. If you aren’t within the search radius, QGIS won’t find and select any vertex for editing, and it will pop up an annoying warning to that effect. Snap tolerance and search radius are set in map units or pixels, so you may find you need to experiment to get them set right. If you specify too big of a tolerance, QGIS may snap to the wrong vertex, especially if you are dealing with a large number of vertices in close proximity. Set search radius too small, and it won’t find anything to move.

The search radius for vertex edits in layer units can be defined in the Digitizing tab under Settings ‣ Options. This is the same place where you define the general, project- wide snapping tolerance.

Ampliando e movendo com a roda do rato¶

While digitizing, you can press the mouse wheel to pan inside of the main window, and you can roll the mouse wheel to zoom in and out on the map. For zooming, place the mouse cursor inside the map area and roll it forward (away from you) to zoom in and backwards (towards you) to zoom out. The mouse cursor position will be the center of the zoomed area of interest. You can customize the behavior of the mouse wheel zoom using the Map tools tab under the Settings ‣ Options menu.

Movendo a direcção com as setas do teclado¶

Panning the map during digitizing 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 without interrupting your digitizing session.

Activar edição topológica¶

The option Enable topological editing is for editing and maintaining common boundaries in polygon mosaics. QGIS ‘detects’ a shared boundary in a polygon mosaic, so you only have to move the vertex once, and QGIS will take care of updating the other boundary.

Evitar intersecções de novos polígonos¶

The second topological option in the Avoid Int. column, called Avoid intersections of new polygons, avoids overlaps in polygon mosaics. It is for quicker digitizing of adjacent polygons. If you already have one polygon, it is possible with this option to digitize the second one such that both intersect, and QGIS then cuts the second polygon to the common boundary. The advantage is that you don’t have to digitize all vertices of the common boundary.

Activar atracção nas intersecções¶

Another option is to use Enable snapping on intersection. It allows you to snap on an intersection of background layers, even if there’s no vertex on the intersection.

Adicionando Elementos¶

Pode usar os ícones ^{Adicionar Elemento}, ^{Adicionar Elemento} ou ^{Adicionar Elemento} da barra de ferramentas para por o cursor QGIS no modo de digitalização.

Para cada elemento, primeiro digitaliza a geometria, e de seguida introduz os atributos. Para digitalizar a geometria, clique com o botão direito do rato na área do mapa para criar o primeiro ponto do seu novo elemento.

Para linhas e polígonos, mantenha o clique com o botão direito do rato para cada ponto adicional que pretende capturar. Quando acabar de adicionar os pontos, clique com o direito do rato em qualquer sítio da área do mapa para confirmar a finalização da introdução da geometria desse elemento.

The attribute window will appear, allowing you to enter the information for the new feature. Figure_edit_2 shows setting attributes for a fictitious new river in Alaska. In the Digitizing menu under the Settings ‣ Options menu, you can also activate Suppress attributes pop-up windows after each created feature and Reuse last entered attribute values.

Figure Edit 2:

Introduza os Valores dos atributos na Janela após a digitalização do novo elemento vectorial

With the ^{Move Feature(s)} icon on the toolbar, you can move existing features.

Edições Actuais¶

This feature allows the digitization of multiple layers. Choose Save for Selected Layers to save all changes you made in multiple layers. You also have the opportunity to Rollback for Selected Layers, so that the digitization may be withdrawn for all selected layers. If you want to stop editing the selected layers, Cancel for Selected Layer(s) is an easy way.

The same functions are available for editing all layers of the project.

Ferramenta de Nós¶

For shapefile-based layers as well as SpatialLite, PostgreSQL/PostGIS, MSSQL Spatial, and Oracle Spatial tables, the ^{Node Tool} provides manipulation capabilities of feature vertices similar to CAD programs. It is possible to simply select multiple vertices at once and to move, add or delete them altogether. The node tool also works with ‘on the fly’ projection turned on, and it supports the topological editing feature. This tool is, unlike other tools in QGIS, persistent, so when some operation is done, selection stays active for this feature and tool. If the node tool is unable to find any features, a warning will be displayed.

It is important to set the property Settings ‣ Options ‣ Digitizing ‣ Search Radius: to a number greater than zero (i.e., 10). Otherwise, QGIS will not be able to tell which vertex is being edited.

Operações Básicas¶

Comece por activar a ^{Ferramenta de Nós} e seleccione um elemento clicando em cima de um, As caixas vermelhos irão aparecer em cada vértice deste elemento.

• Selecting vertices: You can select vertices by clicking on them one at a time, by clicking on an edge to select the vertices at both ends, or by clicking and dragging a rectangle around some vertices. When a vertex is selected, its color changes to blue. To add more vertices to the current selection, hold down the Ctrl key while clicking. Hold down Ctrl or Shift when clicking to toggle the selection state of vertices (vertices that are currently unselected will be selected as usual, but also vertices that are already selected will become unselected).
• Adding vertices: To add a vertex, simply double click near an edge and a new vertex will appear on the edge near to the cursor. Note that the vertex will appear on the edge, not at the cursor position; therefore, it should be moved if necessary.

• Eliminar vértices: Depois de selecionar os vértices para eliminar, clique na tecla Delete. Note-se que não pode usar a ^{Node Tool} para eliminar um elemento completo; QGIS vais assegurar que mantém o número mínimo de vértices necessários para o tipo de elemento que está a trabalhar. Para eliminar um elemente completo, utilize a ferramenta ^{Delete Selected}.

• Mover vértices: Selecione todos os vértices que pretende mover. Clique num vértice selecionado ou na extreminade e arraste na direção que pretende mover. Todos os vértices selecionados serão movidos em conjunto. Se a ferramenta snapping está ativa, toda a seleção pode saltar para o vértice ou linha mais próximos.

Each change made with the node tool is stored as a separate entry in the Undo dialog. Remember that all operations support topological editing when this is turned on. On-the-fly projection is also supported, and the node tool provides tooltips to identify a vertex by hovering the pointer over it.

Cortando, Copiando e Colando Elementos¶

Selected features can be cut, copied and pasted between layers in the same QGIS project, as long as destination layers are set to ^{Toggle editing} beforehand.

Features can also be pasted to external applications as text. That is, the features are represented in CSV format, with the geometry data appearing in the OGC Well-Known Text (WKT) format.

However, in this version of QGIS, text features from outside QGIS cannot be pasted to a layer within QGIS. When would the copy and paste function come in handy? Well, it turns out that you can edit more than one layer at a time and copy/paste features between layers. Why would we want to do this? Say we need to do some work on a new layer but only need one or two lakes, not the 5,000 on our big_lakes layer. We can create a new layer and use copy/paste to plop the needed lakes into it.

As an example, we will copy some lakes to a new layer:

1. Carregue a camada que quer copiar a partir (camada de origem)

2. Carregue ou crie a camada que quer copiar para (camada de destino)

3. Começar a editar a camada de destino

4. Active a camada de origem clicando nela na legenda

5. Use a ferramenta ^{Seleccione Elemento Único} para seleccionar os elemento(s) na camada fonte

6. Clique na ferramenta ^{Copiar Elementos}

7. Active a camada de destino clicando na legenda

8. Clique na ferramenta ^{Colar Elementos}

9. Parar a edição e guardar as alterações

What happens if the source and target layers have different schemas (field names and types are not the same)? QGIS populates what matches and ignores the rest. If you don’t care about the attributes being copied to the target layer, it doesn’t matter how you design the fields and data types. If you want to make sure everything - the feature and its attributes - gets copied, make sure the schemas match.

Apagando os Elementos Seleccionados¶

Se quisermos apagar o polígono todo, podemos faze-lo seleccionando o polígono usando a ferramenta ^{Seleccionar Elemento Único}. Pode seleccionar múltiplos elementos para apagar. Uma vez feita a selecção do conjunto, use a ferramenta ^{Apagar Seleccionados} para apagar os elementos.

The ^{Cut Features} tool on the digitizing toolbar can also be used to delete features. This effectively deletes the feature but also places it on a “spatial clipboard”. So, we cut the feature to delete. We could then use the ^{Paste Features} tool to put it back, giving us a one-level undo capability. Cut, copy, and paste work on the currently selected features, meaning we can operate on more than one at a time.

Guardando as Camadas Editadas¶

When a layer is in editing mode, any changes remain in the memory of QGIS. Therefore, they are not committed/saved immediately to the data source or disk. If you want to save edits to the current layer but want to continue editing without leaving the editing mode, you can click the ^{Save Layer Edits} button. When you turn editing mode off with ^{Toggle editing} (or quit QGIS for that matter), you are also asked if you want to save your changes or discard them.

If the changes cannot be saved (e.g., disk full, or the attributes have values that are out of range), the QGIS in-memory state is preserved. This allows you to adjust your edits and try again.

Retroceder e Retomar¶

The ^Undo and ^Redo tools allows you to undo or redo vector editing operations. There is also a dockable widget, which shows all operations in the undo/redo history (see Figure_edit_3). This widget is not displayed by default; it can be displayed by right clicking on the toolbar and activating the Undo/Redo checkbox. Undo/Redo is however active, even if the widget is not displayed.

Figure Edit 3:

Refazer e desfazer passos de digitalização

When Undo is hit, the state of all features and attributes are reverted to the state before the reverted operation happened. Changes other than normal vector editing operations (for example, changes done by a plugin), may or may not be reverted, depending on how the changes were performed.

To use the undo/redo history widget, simply click to select an operation in the history list. All features will be reverted to the state they were in after the selected operation.

Rodar Elemento(s)¶

Use ^{Rotate Feature(s)} to rotate one or multiple selected features in the map canvas. You first need to select the features and then press the ^{Rotate Feature(s)} icon. The centroid of the feature(s) appears and will be the rotation anchor point. If you selected multiple features, the rotation anchor point will be the common center of the features. Press and drag the left mouse button in the desired direction to rotate the selected features.

It’s also possible to create a user-defined rotation anchor point around which the selected feature will rotate. Select the features to rotate and activate the ^{Rotate Feature(s)} tool. Press and hold the Ctrl button and move the mouse pointer (without pressing the mouse button) to the place where you want the rotation anchor to be moved. Release the Ctrl button when the desired rotation anchor point is reached. Now, press and drag the left mouse button in the desired direction to rotate the selected feature(s).

Simplificar elemento¶

The ^{Simplify Feature} tool allows you to reduce the number of vertices of a feature, as long as the geometry doesn’t change and geometry type is not a multi geometry. First, select a feature. It will be highlighted by a red rubber band and a slider will appear. Moving the slider, the red rubber band will change its shape to show how the feature is being simplified. Click [OK] to store the new, simplified geometry. If a feature cannot be simplified (e.g. multi-polygons), a message will appear.

Adicionar Anél¶

You can create ring polygons using the ^{Add Ring} icon in the toolbar. This means that inside an existing area, it is possible to digitize further polygons that will occur as a ‘hole’, so only the area between the boundaries of the outer and inner polygons remains as a ring polygon.

Adicionar Parte¶

You can ^{add part} polygons to a selected multipolygon. The new part polygon must be digitized outside the selected multi-polygon.

Fill Ring¶

You can use the ^{Fill Ring} function to add a ring to a polygon and add a new feature to the layer at the same time. Thus you need not first use the ^{Add Ring} icon and then the ^{Add feature} function anymore.

Apagar Anél¶

The ^{Delete Ring} tool allows you to delete ring polygons inside an existing area. This tool only works with polygon layers. It doesn’t change anything when it is used on the outer ring of the polygon. This tool can be used on polygon and multi-polygon features. Before you select the vertices of a ring, adjust the vertex edit tolerance.

Apagar Parte¶

The ^{Delete Part} tool allows you to delete parts from multifeatures (e.g., to delete polygons from a multi-polygon feature). It won’t delete the last part of the feature; this last part will stay untouched. This tool works with all multi-part geometries: point, line and polygon. Before you select the vertices of a part, adjust the vertex edit tolerance.

Refazer elementos¶

You can reshape line and polygon features using the ^{Reshape Features} icon on the toolbar. It replaces the line or polygon part from the first to the last intersection with the original line. With polygons, this can sometimes lead to unintended results. It is mainly useful to replace smaller parts of a polygon, not for major overhauls, and the reshape line is not allowed to cross several polygon rings, as this would generate an invalid polygon.

Por exemplo, pode editar o limite de um polígono com esta ferramenta. Primeiro, clique na área interna do polígos junto do ponto onde pretende adicionar o novo vértice. Depois, atravesse o limite e adicione os vértices no exterior do polígono. Para finalizar, clique com o botão direito na área interna do polígono. A ferramente vai adicionar um nó automaticamente no ponto onde a linha atravessa o limite. Também é possível remover parte da área do polígono, começa-se a nova linha no exterior do polígono, adicionam-se vértices no interior e termina-se a linha no exterior do polígono com um clique no botão direito.

Curvas de Afastamento¶

The ^{Offset Curve} tool creates parallel shifts of line layers. The tool can be applied to the edited layer (the geometries are modified) or also to background layers (in which case it creates copies of the lines / rings and adds them to the the edited layer). It is thus ideally suited for the creation of distance line layers. The displacement is shown at the bottom left of the taskbar.

To create a shift of a line layer, you must first go into editing mode and then select the feature. You can make the ^{Offset Curve} tool active and drag the cross to the desired distance. Your changes may then be saved with the ^{Save Layer Edits} tool.

QGIS options dialog (Digitizing tab then Curve offset tools section) allows you to configure some parameters like Join style, Quadrant segments, Miter limit.

Dividir Elementos¶

Pode dividir elementos usando o ícone ^{Dividir Elementos} da barra de ferramentas. Apenas desenhe uma linha ao longo do elemento que quer dividir.

Split parts¶

In QGIS 2.0 it is now possible to split the parts of a multi part feature so that the number of parts is increased. Just draw a line across the part you want to split using the ^{Split Parts} icon.

Juntar elementos seleccionados¶

The ^{Merge Selected Features} tool allows you to merge features that have common boundaries. A new dialog will allow you to choose which value to choose between each selected features or select a fonction (Minimum, Maximum, Median, Sum, Skip Attribute) to use for each column.

Juntar os atributos dos elementos seleccionados¶

The ^{Merge Attributes of Selected Features} tool allows you to merge attributes of features with common boundaries and attributes without merging their boundaries. First, select several features at once. Then press the ^{Merge Attributes of Selected Features} button. Now QGIS asks you which attributes are to be applied to all selected objects. As a result, all selected objects have the same attribute entries.

Rodar Símbolos de Pontos¶

^{Rotate Point Symbols} allows you to change the rotation of point symbols in the map canvas. You must first define a rotation column from the attribute table of the point layer in the Advanced menu of the Style menu of the Layer Properties. Also, you will need to go into the ‘SVG marker’ and choose Data defined properties .... Activate Angle and choose ‘rotation’ as field. Without these settings, the tool is inactive.

Figure Edit 4:

Rodar Símbolos de Pontos

To change the rotation, select a point feature in the map canvas and rotate it, holding the left mouse button pressed. A red arrow with the rotation value will be visualized (see Figure_edit_4). When you release the left mouse button again, the value will be updated in the attribute table.

Criando uma nova camada Shapefile¶

To create a new shape layer for editing, choose New ‣ New Shapefile Layer... from the Layer menu. The New Vector Layer dialog will be displayed as shown in Figure_edit_5. Choose the type of layer (point, line or polygon) and the CRS (coordinate reference system).

Note that QGIS does not yet support creation of 2.5D features (i.e., features with X,Y,Z coordinates).

Figure Edit 5:

Janela de criação de uma nova camada Shapefile

To complete the creation of the new shapefile layer, add the desired attributes by clicking on the [Add to attributes list] button and specifying a name and type for the attribute. A first ‘id’ column is added as default but can be removed, if not wanted. Only Type: real , Type: integer , Type: string and Type:date attributes are supported. Additionally and according to the attribute type, you can also define the width and precision of the new attribute column. Once you are happy with the attributes, click [OK] and provide a name for the shapefile. QGIS will automatically add a .shp extension to the name you specify. Once the layer has been created, it will be added to the map, and you can edit it in the same way as described in section Digitalizar uma camada existente above.

Criando uma nova camada SpatialLite¶

Para criar uma nova camada SpatialLite para edição, escolha Novo ‣ Nova Camada SpatiaLite... do menu Camada. O diálogo Nova Camada SpatiaLite irá aparecer como é mostrado na Figure_edit_6.

Figure Edit 6:

Janela de criação de uma nova camada SpatialLite

The first step is to select an existing SpatiaLite database or to create a new SpatiaLite database. This can be done with the browse button to the right of the database field. Then, add a name for the new layer, define the layer type, and specify the coordinate reference system with [Specify CRS]. If desired, you can select Create an autoincrementing primary key.

To define an attribute table for the new SpatiaLite layer, add the names of the attribute columns you want to create with the corresponding column type, and click on the [Add to attribute list] button. Once you are happy with the attributes, click [OK]. QGIS will automatically add the new layer to the legend, and you can edit it in the same way as described in section Digitalizar uma camada existente above.

Further management of SpatiaLite layers can be done with the DB Manager. See Módulo Gestor BD.

Criando uma nova camada GPX¶

To create a new GPX file, you need to load the GPS plugin first. Plugins ‣ Plugin Manager... opens the Plugin Manager Dialog. Activate the GPS Tools checkbox.

When this plugin is loaded, choose New ‣ Create new GPX Layer... from the Layer menu. In the Save new GPX file as dialog, you can choose where to save the new GPX layer.

Seleccionando elementos na tabela de atributos¶

Cada linha selecionada na tabela de atributos representa os atributos de um determinado elemento da camada. Se o conjunto de elementos selecionados na janela principal é alterado, a seleção também é atualizada na tabela de atributos. Da mesma forma, se um conjunto de linhas selecionadas na tabela de atributos é modificada, o conjunto de elementos selecionado na janela principal será atualizado.

As linhas podem ser selecionadas ao clicar no número da linha, do lado esquerdo desta. Podem ser marcadas Linhas múltiplas manter a tecla Ctrl primida. Pode ser feita uma seleção contínua se manter primida a tecla Shift e clicar na entrada de várias linha, do lado esquerdo. Todas as linhas entre a posição atual do cursor e a linha clicada serão selecionados. Ao mover a posição do cursor na tabela de atributos, ao clicar um célula na tabela, não tem influência na seleção de linhas. Modificar a seleção na tela principal não altera a posição do cursor na tabela de atributos.

A tabela pode ser ordenada por qualquer coluna, clicando no cabeçalho da coluna. Uma pequena seta indica a forma de ordenação (apontar para baixo significa valores descendentes do topo da linha, apontar para cima significa valores descendentes do topo da linha).

For a simple search by attributes on only one column, choose the Column filter ‣ from the menu in the bottom left corner. Select the field (column) on which the search should be performed from the drop-down menu, and hit the [Apply] button. Then, only the matching features are shown in the attribute table.

To make a selection, you have to use the ^{Select features using an Expression} icon on top of the attribute table. ^{Select features using an Expression} allows you to define a subset of a table using a Function List like in the ^{Field Calculator} (see Calculadora de Campos). The query result can then be saved as a new vector layer. For example, if you want to find regions that are boroughs from regions.shp of the QGIS sample data, you have to open the Fields and Values menu and choose the field that you want to query. Double-click the field ‘TYPE_2’ and also [Load all unique values] . From the list, choose and double-click ‘Borough’. In the Expression field, the following query appears:

"TYPE_2"  =  'Borough'

Here you can also use the Function list ‣ Recent (Selection) to make a selection that you used before. The expression builder remembers the last 20 used expressions.

The matching rows will be selected, and the total number of matching rows will appear in the title bar of the attribute table, as well as in the status bar of the main window. For searches that display only selected features on the map, use the Query Builder described in section Ferramenta de Consulta.

To show selected records only, use Show Selected Features from the menu at the bottom left.

The other buttons at the top of the attribute table window provide the following functionality:

• ^{Toggle editing mode} to edit single values and to enable functionalities described below (also with Ctrl+E)
• ^{Save Edits} (also with Ctrl+S)
• ^{Unselect all} (also with Ctrl+U)
• ^{Move selected to top} (also with Ctrl+T)
• ^{Invert selection} (also with Ctrl+R)
• ^{Copy selected rows to clipboard} (also with Ctrl+C)
• ^{Zoom map to the selected rows} (also with Ctrl+J)
• ^{Pan map to the selected rows} (also with Ctrl+P)
• ^{Delete selected features} (also with Ctrl+D)
• ^{New Column} for PostGIS layers and for OGR layers with GDAL version >= 1.6 (also with Ctrl+W)
• ^{Delete Column} for PostGIS layers and for OGR layers with GDAL version >= 1.9 (also with Ctrl+L)
• ^{Open field calculator} (also with Ctrl+I)

Below these buttons is the Field Calculator bar, which allows calculations to be quickly applied attributes visible in the table. This bar uses the same expressions as the ^{Field Calculator} (see Calculadora de Campos).

Guardar elementos seleccionados como nova camada¶

The selected features can be saved as any OGR-supported vector format and also transformed into another coordinate reference system (CRS). Just open the right mouse menu of the layer and click on Save as to define the name of the output file, its format and CRS (see section Legenda do Mapa). To save the selection ensure that the Save only selected features is selected. It is also possible to specify OGR creation options within the dialog.

Paste into new layer¶

Features that are on the clipboard may be pasted into a new layer. To do this, first make a layer editable. Select some features, copy them to the clipboard, and then paste them into a new layer using Edit ‣ Paste Features as and choosing New vector layer or New memory layer.

This applies to features selected and copied within QGIS and also to features from another source defined using well-known text (WKT).

Trabalhando com tabelas de atributos não espaciais¶

QGIS allows you also to load non-spatial tables. This currently includes tables supported by OGR and delimited text, as well as the PostgreSQL, MSSQL and Oracle provider. The tables can be used for field lookups or just generally browsed and edited using the table view. When you load the table, you will see it in the legend field. It can be opened with the ^{Open Attribute Table} tool and is then editable like any other layer attribute table.

As an example, you can use columns of the non-spatial table to define attribute values, or a range of values that are allowed, to be added to a specific vector layer during digitizing. Have a closer look at the edit widget in section Menu Campos to find out more.

Foreign keys¶

Then you get another point layer or table with information about airports that are located in the regions and you also want to keep track of these. If you want to add them to the region layer, you need to create a one to many relation using foreign keys, because there are several airports in most regions.

Figure Relations 1:

Alaska region with airports

In addition to the already existing attributes in the airports attribute table another field fk_region which acts as a foreign key (if you have a database, you will probably want to define a constraint on it).

This field fk_region will always contain an id of a region. It can be seen like a pointer to the region it belongs to. And you can design a custom edit form for the editing and QGIS takes care about the setup. It works with different providers (so you can also use it with shape and csv files) and all you have to do is to tell QGIS the relations between your tables.

Layers¶

QGIS makes no difference between a table and a vector layer. Basically, a vector layer is a table with a geometry. So can add your table as a vector layer. To demostrate you can load the ‘region’ shapefile (with geometries) and the ‘airport’ csv table (without geometries) and a foreign key (fk_region) to the layer region. This means, that each airport belongs to exactly one region while each region can have any number of airports (a typical one to many relation).

Definition (Relation Manager)¶

The first thing we are going to do is to let QGIS know about the relations between the layer. This is done in Settings ‣ Project Properties. Open the Relations menu and click on Add.

• name is going to be used as a title. It should be a human readable string, describing, what the relation is used for. We will just call say “Airports” in this case.
• referencing layer is the one with the foreign key field on it. In our case this is the airports layer
• referencing field will say, which field points to the other layer so this is fk_region in this case
• referenced layer is the one with the primary key, pointed to, so here it is the regions layer
• referenced field is the primary key of the referenced layer so it is ID
• id will be used for internal purposes and has to be unique. You may need it to build custom forms once this is supported. If you leave it empty, one will be generated for you but you can assign one yourself to get one that is easier to handle.

Figure Relations 2:

Relation Manager

Forms¶

Now that QGIS knows about the relation, it will be used to improve the forms it generates. As we did not change the default form method (autogenerated) it will just add a new widget in our form. So let’s select the layer region in the legend and use the identify tool. Depending on your settings, the form might open directly or you will have to choose to open it in the identification dialog under actions.

Figure Relations 3:

Identification dialog regions with relation to airports

As you can see, the airports assigned to this particular region are all shown in a table. And there are also some buttons available. Let’s review them shortly

• The button is for toggling the edit mode. Be aware that it toggles the edit mode of the airport layer, although we are in the feature form of a feature from the region layer. But the table is representing features of the airport layer.
• The button will add a new feature to the airport layer. And it will assign the new airport to the current region by default.
• The button will delete the selected airport permanently.
• The symbol will open a new dialog where you can select any existing airport which will then be assigned to the current region. This may be handy if you created the airport on the wrong region by accident.
• The symbol will unlink the selected airport from the current region, leaving them unassigned (the foreign key is set to NULL) effectively.
• The two buttons to the right switch between table view and form view where the later let’s you view all the airports in their respective form.

If you work on the airport table, a new widget type is available which lets you embed the feature form of the referenced region on the feature form of the airports. It can be used when you open the layer properties of the airports table, switch to the Fields menu and change the widget type of the foreign key field ‘fk_region’ to Relation Reference.

If you look at the feature dialog now, you will see, that the form of the region is embedded inside the airports form and will even have a combobox, which allows you to assign the current airport to another region.

Figure Relations 4:

Identification dialog airport with relation to regions