Working with Project Files

Introducing QGIS projects

The state of your QGIS session is called a project. QGIS works on one project at a time. Any settings can be project-specific or an application-wide default for new projects (see section Options). QGIS can save the state of your workspace into a project file using the menu options Project ‣ fileSave Save or Project ‣ fileSaveAs Save As....

注解

If the project you loaded has been modified in the meantime, by default, QGIS will ask you if you want to overwrite the changes. This behavior is controlled by the checkbox Prompt to save project and data source changes when required setting under Settings ‣ Options ‣ General menu.

You can load existing projects into QGIS using Project ‣ fileOpen Open..., Project ‣ New from template or Project ‣ Open Recent ‣.

At startup, a list of recently opened projects is displayed, including screenshots, names and file paths (for up to ten projects). This is a handy quick way to access recently used projects. Double-click an entry in this list to open the corresponding project. If you instead want to create a new project, just add any layer and the list disappears, giving way to the map canvas.

If you want to clear your session and start fresh, go to Project ‣ fileNew New. This will prompt you to save the existing project if changes have been made since it was opened or last saved.

../../../_images/new_project.png

Starting a new project in QGIS

The information saved in a project file includes:

  • Layers added

  • Which layers can be queried

  • Layer properties, including symbolization and styles

  • Projection for the map view

  • Last viewed extent

  • Print layouts

  • Print layout elements with settings

  • Print layout atlas settings

  • Digitizing settings

  • Table Relations

  • Project Macros

  • Project default styles

  • Plugins settings

  • QGIS Server settings from the OWS settings tab in the Project properties

  • Queries stored in the DB Manager

The project file is saved in XML format. This means that it is possible to edit the file outside of QGIS if you know what you are doing. The file format has been updated several times compared with earlier QGIS versions. Project files from older QGIS versions may not work properly any more.

注解

By default, QGIS will warn you of version differences. This behavior is controlled in Settings ‣ Options. On the General tab, you should tick checkbox Warn when opening a project file saved with an older version of QGIS.

Whenever you save a .qgs project in QGIS, a backup of the project file is created with the extension .qgs~ and stored in the same directory as the project file.

The extension for QGIS projects is .qgs but when saving from QGIS, the default is to save using a compressed format with the .qgz extension. The .qgs file is embedded in the .qgz file (a zip archive), together with its associated sqlite database (.qgd) for auxiliary data. You can get to these files by unzipping.

注解

A zipped project may be particularly useful with the Auxiliary Storage Properties mechanism in order to embed the underlying database.

Projects can also be saved/loaded to/from a PostgreSQL database using the following Project menu items:

  • Project ‣ Open from

  • Project ‣ Save to

Both menu items have a sub-menu with a list of extra project storage implementations (currently just PostgreSQL). Clicking the action will open a dialog to pick a PostgreSQL connection name, schema name and project.

Projects stored in PostgreSQL can be also loaded from the QGIS browser panel (the entries are located within the schema they are stored in), either by double-clicking them or by dragging them to the map canvas.

Generating output

There are several ways to generate output from your QGIS session. We have already discussed saving as a project file in Introducing QGIS projects. Other ways to produce output files are:

  • Creating images: Project ‣ Import/Export ‣ saveMapAsImage Export Map to Image... opens a file dialog where you select the name, path and type of image (PNG, JPG and many other formats). This will also create a world file (with extension PNGW or JPGW) that is saved in the same folder as your image. This world file is used to georeference the image.

  • Exporting to DXF files: Project ‣ Import/Export ‣ Export Project to DXF... opens a dialog where you can define the 'Symbology mode', the 'Symbology scale' and vector layers you want to export to DXF. Through the 'Symbology mode' symbols from the original QGIS Symbology can be exported with high fidelity (see section Creating new DXF files).

  • Exporting to PDF files: Project ‣ Import/Export ‣ Export Map to PDF... opens a dialog where you can define the part (Extent) of the map to be exported, the Scale, Resolution, Output width (pixels) and Output height (pixels). You can also choose to Draw active decorations and Draw annotations, as well as Rasterize map.

  • Designing print maps: Project ‣ newLayout New Print Layout... opens a dialog where you can layout and print the current map canvas (see section Laying out the maps).