Как сделать прилипание в qgis

14.4. Редактирование¶

QGIS has various capabilities for editing OGR, SpatiaLite, PostGIS, MSSQL Spatial and Oracle Spatial vector layers and tables.

Параллельное редактирование

This version of QGIS does not track if somebody else is editing the same feature at the same time as you are. The last person to save the edits wins.

14.4.1. Настройка порога прилипания и радиуса поиска¶

For optimal and accurate editing of vector layer geometries, we need to set an appropriate value of snapping tolerance and search radius for features vertices.

14.4.1.1. Порог прилипания¶

When you add a new vertex or move an existing one, the snapping tolerance is the distance QGIS uses to search for the closest vertex or segment you are trying to connect to. If you are not within the snapping tolerance, QGIS will leave the vertex where you release the mouse button, instead of snapping it to an existing vertex or segment.

The snapping tolerance setting affects all tools that work with tolerance.

There are three options to select the layer(s) to snap to:

All layers : quick setting for all visible layers in the project so that the pointer snaps to all vertices and/or segments. In most cases, it is sufficient to use this snapping mode, but beware when using it for projects with many vector layers, as it may affect performance.

Current layer : only the active layer is used, a convenient way to ensure topological consistency within the layer being edited.

Advanced Configuration : allows you to enable and adjust snapping mode and tolerance on a layer basis (see figure_edit_snapping). If you need to edit a layer and snap its vertices to another, make sure that the target layer is checked and increase the snapping tolerance to a higher value. Snapping will not occur to a layer that is not checked in the snapping options dialog.

Рис. 14.85 Snapping options (Advanced Configuration mode) ¶

By default, only visible features (the features whose style is displayed, except for layers where the symbology is «No symbols») can be snapped. You can enable the snapping on invisible features by checking Enable snapping on invisible features under the Settings ▶ Options ▶ Digitizing tab.

Enable snapping by default

You can set snapping to be enabled by default on all new projects in the Settings ▶ Options ▶ Digitizing tab. You can also set the default snapping mode, tolerance value, and units, which will populate the Snapping Options dialog.

14.4.1.2. Активация прилипания к пересечениям¶

14.4.1.3. Радиус поиска¶

Search radius for vertex edits is the distance QGIS uses to search for the vertex to select when you click on the map. If you are not within the search radius, QGIS will not find and select any vertex for editing. The search radius for vertex edits can be defined under the Settings ▶ Options ▶ Digitizing tab (this is where you define the snapping default values).

14.4.2. Топологическое редактирование¶

In addition to these snapping options, the Snapping options… dialog ( Project ▶ Snapping options ) and the Snapping toolbar allow you to enable / disable some other topological functionalities.

14.4.2.1. Включение топологического редактирования¶

Topological editing works with features from different layers, as long as the layers are visible and in editing mode.

14.4.2.2. Avoid overlap of new polygons¶

With avoid overlap enabled, if you already have one polygon, you can digitize a second one such that they intersect. QGIS will then cut the second polygon to the boundary of the existing one. The advantage is that you don’t have to digitize all vertices of the common boundary.

If the new geometry is totally covered by existing ones, it gets cleared, and QGIS will show an error message.

Use cautiously the Avoid overlap option

Since this option will cut new overlapping geometries of any polygon layer, you can get unexpected geometries if you forget to uncheck it when no longer needed.

14.4.2.3. Geometry Checker¶

14.4.2.4. Automatic Tracing¶

Usually, when using capturing map tools (add feature, add part, add ring, reshape and split), you need to click each vertex of the feature. With the automatic tracing mode, you can speed up the digitization process as you no longer need to manually place all the vertices during digitization:

Enable the Tracing tool (in the Snapping toolbar) by pushing the icon or pressing T key.

Snap to a vertex or segment of a feature you want to trace along.

Move the mouse over another vertex or segment you’d like to snap and, instead of the usual straight line, the digitizing rubber band represents a path from the last point you snapped to the current position.

QGIS actually uses the underlying features topology to build the shortest path between the two points. Tracing requires snapping to be activated in traceable layers to build the path. You should also snap to an existing vertex or segment while digitizing and ensure that the two nodes are topologically connectable through existing features edges, otherwise QGIS is unable to connect them and thus traces a single straight line.

Click and QGIS places the intermediate vertices following the displayed path.

Unfold the Enable Tracing icon and set the Offset option to digitize a path parallel to the features instead of tracing along them. A positive value shifts the new drawing to the left side of the tracing direction and a negative value does the opposite.

Adjust map scale or snapping settings for an optimal tracing

If there are too many features in map display, tracing is disabled to avoid potentially long tracing structure preparation and large memory overhead. After zooming in or disabling some layers the tracing is enabled again.

Does not add topological points

This tool does not add points to existing polygon geometries even if Topological editing is enabled. If geometry precision is activated on the edited layer, the resulting geometry might not exactly follow an existing geometry.

Quickly enable or disable automatic tracing by pressing the T key

By pressing the T key, tracing can be enabled/disabled anytime (even while digitizing a feature), so it is possible to digitize parts of the feature with tracing enabled and other parts with tracing disabled. Tools behave as usual when tracing is disabled.

14.4.3. Редактирование существующего слоя¶

By default, QGIS loads layers read-only. This is a safeguard to avoid accidentally editing a layer if there is a slip of the mouse. However, you can choose to edit any layer as long as the data provider supports it (see Exploring Data Formats and Fields ), and the underlying data source is writable (i.e., its files are not read-only).

Restrict edit permission on layers within a project

From the Project ▶ Properties… ▶ Data Sources ▶ Layers Capabilities table, you can choose to set any layer read-only regardless the provider permission. This can be a handy way, in a multi-users environment to avoid unauthorized users to mistakenly edit layers (e.g., Shapefile), hence potentially corrupt data. Note that this setting only applies inside the current project.

Using the basic digitizing tools, you can perform the following functions:

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Редактирование¶

QGIS supports various capabilities for editing OGR, SpatiaLite, PostGIS, MSSQL Spatial and Oracle Spatial vector layers and tables.

Параллельное редактирование

This version of QGIS does not track if somebody else is editing the same feature at the same time as you are. The last person to save its edits wins.

Настройка порога прилипания и радиуса поиска¶

For an optimal and accurate edit of the vector layer geometries, we need to set an appropriate value of snapping tolerance and search radius for features vertices.

Порог прилипания¶

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.

Figure Edit 1:

Edit snapping options on a layer basis (Advanced mode)

Control the list of layers to snap

Радиус поиска¶

Search radius is the distance QGIS uses to search for the closest vertex you are trying to select when you click on the map. If you aren’t within the search radius, QGIS won’t find and select any vertex for editing. 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.

Топологическое редактирование¶

Besides layer-based snapping options, you can also define topological functionalities in the Snapping options. dialog in the Settings (or File) menu. Here, you can define Enable topological editing, and/or for polygon layers, activate the Avoid Intersections option.

Включение топологического редактирования¶

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

Предотвращение пересечения новых полигонов¶

A second topological option called Avoid intersections prevents you to draw new features that overlap an existing one. 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 boundary of the existing one. The advantage is that you don’t have to digitize all vertices of the common boundary.

If the new geometry is totally covered by existing ones, it gets cleared and the new feature will have no geometry when allowed by the provider, otherwise saving modifications will make QGIS pop-up an error message.

Use cautiously the Avoid Intersections option

Because the option cuts or clears geometry of any overlaping feature from any polygon layer, do not forget to uncheck this option once you no longer need it otherwise, you can get unexpected geometries.

Активация прилипания к пересечениям¶

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.

Geometry Checker¶

A core plugin can help the user to find the geometry invalidity. You can find more information on this plugin at Geometry Checker Plugin.

Редактирование существующего слоя¶

By default, QGIS loads layers read-only. This is a safeguard to avoid accidentally editing a layer if there is a slip of the mouse. However, you can choose to edit any layer as long as the data provider supports it, and the underlying data source is writable (i.e., its files are not read-only).

In general, tools for editing vector layers are divided into a digitizing and an advanced digitizing toolbar, described in section Дополнительные функции оцифровки. You can select and unselect both under View ‣ Toolbars ‣. Using the basic digitizing tools, you can perform the following functions:

Add Feature: Capture PointAdd Feature: Capture LineAdd Feature: Capture Polygon

Основные инструменты редактирования векторного слоя

Note that while using any of the digitizing tools, you can still zoom or pan in the map canvas without losing the focus on the tool.

All editing sessions start by choosing the Toggle editing option found in the context menu of a given layer, from the attribute table dialog, the digitizing toolbar or the Edit menu.

Once the layer is in edit mode, additional tool buttons on the editing toolbar will become available and markers will appear at the vertices of all features unless Show markers only for selected features option under Settings ‣ Options. ‣ Digitizing menu is checked.

Регулярное сохранение

Remember to Save Layer Edits regularly. This will also check that your data source can accept all the changes.

Добавление объектов¶

The next buttons Add circular string or Add circular string by radius allow users to add line or polygon features with a circular geometry.

To create features with these tools, you first digitize the geometry then enter its attributes. To digitize the geometry, left-click on the map area to create the first point of your new feature.

For linear or curved geometries, keep on left-clicking for each additional point you wish to capture or use automatic tracing capability to accelerate the digitization. You can switch back and forth between linear Add feature tool and curved Add circular string. tools to create compound curved geometry. Pressing Delete or Backspace key reverts the last node you add. When you have finished adding points, right-click anywhere on the map area to confirm you have finished entering the geometry of that feature.

Curved geometries are stored as such only in compatible data provider

Although QGIS allows to digitize curved geometries within any editable data format, you need to be using a data provider (e.g. PostGIS, GML or WFS) that supports curves to have features stored as curved, otherwise QGIS segmentizes the circular arcs. The memory layer provider also supports curves.

Customize the digitizing rubber band

While capturing polygon, the by-default red rubber band can hide underlying features or places you’d like to capture a point. This can be fixed by setting a lower opacity (or alpha channel) to the rubber band’s Fill Color in Settings ‣ Options ‣ Digitizing menu. You can also avoid the use of the rubber band by checking Don’t update rubber band during node editing.

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. However, in the Digitizing menu under the Settings ‣ Options menu, you can also activate:

Figure Edit 2:

Enter Attribute Values Dialog after digitizing a new vector feature

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

Редактирование узлов¶

For shapefile-based or MapInfo layers as well as SpatiaLite, 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 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.

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

Маркировка вершин

The current version of QGIS supports three kinds of vertex markers: ‘Semi-transparent circle’, ‘Cross’ and ‘None’. To change the marker style, choose Options from the Settings menu, click on the Digitizing tab and select the appropriate entry.

Основные операции¶

Start by activating the Node Tool and selecting a feature by clicking on it. Red boxes will appear at each vertex of this feature.

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.

Move features with precision

The Vertex Editor¶

With activating the Node Tool on a feature, QGIS opens the Vertex Editor panel listing all the vertices of the feature with their x, y (z, m if applicable) coordinates and r (for the radius, in case of circular geometry). Simply select a row in the table does select the corresponding vertex in the map canvas, and vice versa. Simply change a coordinate in the table and your vertex position is updated. You can also select multiple rows and delete them altogether.

Figure Edit 3:

Vertex editor panel showing selected nodes

Вырезать, копировать и вставить объекты¶

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.

Transform polygon into line and vice-versa using copy/paste

Copy a line feature and paste it in a polygon layer: QGIS pastes in the target layer a polygon whose boundary corresponds to the closed geometry of the line feature. This is a quick way to generate different geometries of the same data.

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. WKT features from outside QGIS can also 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:

Загрузите слой, из которого вы собираетесь копировать (исходный слой)

Загрузите или создайте слой, в который вы будете копировать (целевой слой)

Начаните редактирование целевого слоя

Активируйте исходный слой щелчком мыши по нему в легенде

Сделайте активным целевой слой, щелкнув по нему в легенде кнопкой мыши

Завершите редактирование и сохраните изменения

Соответствие вставляемых объектов

If your source and destination layers use the same projection, then the pasted features will have geometry identical to the source layer. However, if the destination layer is a different projection, then QGIS cannot guarantee the geometry is identical. This is simply because there are small rounding-off errors involved when converting between projections.

Copy string attribute into another

If you have created a new column in your attribute table with type ‘string’ and want to paste values from another attribute column that has a greater length the length of the column size will be extended to the same amount. This is because the GDAL Shapefile driver starting with GDAL/OGR 1.10 knows to auto-extend string and integer fields to dynamically accommodate for the length of the data to be inserted.

Удаление выделенных объектов¶

If we want to delete an entire feature (attribute and geometry), we can do that by first selecting the geometry using the regular Select Features by area or single click tool. Selection can also be done from the attribute table. Once you have the selection set, press Delete or Backspace key or use the Delete Selected tool to delete the features. Multiple selected features can be deleted at once.

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.

Сохранение отредактированных слоев¶

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.

Целостность данных

It is always a good idea to back up your data source before you start editing. While the authors of QGIS have made every effort to preserve the integrity of your data, we offer no warranty in this regard.

Saving multiple layers at once¶

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.

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