15.1. Deschiderea datelor

Ca parte a unui ecosistem Software cu Sursă Deschisă, QGIS este construit pe diferite biblioteci care, combinate cu furnizorii proprii, oferă posibilități de a citi și de a scrie într-o mulțime de formate:

• Vector data formats include GeoPackage, GML, GeoJSON, GPX, KML, Comma Separated Values, ESRI formats (Shapefile, Geodatabase…), MapInfo and MicroStation file formats, AutoCAD DWG/DXF, GRASS and many more… Read the complete list of supported vector formats.

• Raster data formats include GeoTIFF, JPEG, ASCII Gridded XYZ, MBTiles, R or Idrisi rasters, GDAL Virtual, SRTM, Sentinel Data, ERDAS IMAGINE, ArcInfo Binary Grid, ArcInfo ASCII Grid, and many more… Read the complete list of supported raster formats.

• Database formats include PostgreSQL/PostGIS, SQLite/SpatiaLite, Oracle, MS SQL Server, SAP HANA, MySQL…

• Web map and data services (WM(T)S, WFS, WCS, CSW, XYZ tiles, ArcGIS services, …) are also handled by QGIS providers. See Working with OGC / ISO protocols for more information about some of these.

• You can read supported files from archived folders and use QGIS native formats such as QML files (QML - Formatul Fișierelor de Stilizare) and virtual and memory layers.

More than 80 vector and 140 raster formats are supported by GDAL and QGIS native providers.

Notă

Not all of the listed formats may work in QGIS for various reasons. For example, some require external proprietary libraries, or the GDAL/OGR installation of your OS may not have been built to support the format you want to use. To see the list of available formats, run the command line ogrinfo --formats (for vector) and gdalinfo --formats (for raster), or check the Settings ► Options ► GDAL menu in QGIS.

In QGIS, depending on the data format, there are different tools to open a dataset, mainly available in the Layer ► Add Layer ► menu or from the Manage Layers toolbar (enabled through View ► Toolbars menu). However, all these tools point to a unique dialog, the Data Source Manager dialog, that you can open with the ^{Open Data Source Manager} button, available on the Data Source Manager Toolbar, or by pressing Ctrl+L. The Data Source Manager dialog (Fig. 15.1) offers a unified interface to open file-based data as well as databases or web services supported by QGIS.

Fig. 15.1 QGIS Data Source Manager dialog

Beside this main entry point, you also have the DB Manager plugin that offers advanced capabilities to analyze and manipulate connected databases. More information on DB Manager capabilities can be found in DB Manager Plugin.

There are many other tools, native or third-party plugins, that help you open various data formats.

This chapter will describe only the tools provided by default in QGIS for loading data. It will mainly focus on the Data Source Manager dialog but more than describing each tab, it will also explore the tools based on the data provider or format specificities.

15.1.1. Panoul Navigatorului

The Browser is one of the main ways to quickly and easily add your data to projects. It’s available as:

• a Data Source Manager tab, enabled pressing the ^{Open Data Source Manager} button (Ctrl+L);

• as a QGIS panel you can open from the menu View ► Panels (or Settings ► Panels) or by pressing Ctrl+2.

In both cases, the Browser helps you navigate in your file system and manage geodata, regardless the type of layer (raster, vector, table), or the datasource format (plain or compressed files, databases, web services).

15.1.1.1. Exploring the Interface

At the top of the Browser panel, you find some buttons that help you to:

• ^{Add Selected Layers}: you can also add data to the map canvas by selecting Add selected layer(s) from the layer’s context menu;

• ^Refresh the browser tree;

• ^{Filter Browser} to search for specific data. Enter a search word or wildcard and the browser will filter the tree to only show paths to matching DB tables, filenames or folders – other data or folders won’t be displayed. See the Browser Panel(2) example in Fig. 15.2. The comparison can be case-sensitive or not. It can also be set to:

  • Normal: show items containing the search text

  • Wildcard(s): fine tune the search using the ? and/or * characters to specify the position of the search text

  • Regular expression

• ^{Collapse All} the whole tree;

• ^{Enable/disable properties widget}: when toggled on, a new widget is added at the bottom of the panel showing, if applicable, metadata for the selected item.

The entries in the Browser panel are organised hierarchically, and there are several top level entries:

1. Favorites where you can place shortcuts to often used locations

2. Spatial Bookmarks where you can store often used map extents (see Bookmarking extents on the map)

3. Project Home: for a quick access to the folder in which (most of) the data related to your project are stored. The default value is the directory where your project file resides.

4. Home directory in the file system and the filesystem root directory.

5. Connected local or network drives

6. Then comes a number of container / database types and service protocols, depending on your platform and underlying libraries:

   • GeoPackage

   • SpatiaLite

   • PostgreSQL

   • SAP HANA

   • MS SQL Server

   • Oracle

   • WMS/WMTS

   • Vector Tiles

   • XYZ Tiles

   • WCS

   • WFS/OGC API-Features

   • ArcGIS REST Server

   • GeoNode

15.1.1.2. Interacting with the Browser items

The browser supports drag and drop within the browser, from the browser to the canvas and Layers panel, and from the Layers panel to layer containers (e.g. GeoPackage) in the browser.

Project file items inside the browser can be expanded, showing the full layer tree (including groups) contained within that project. Project items are treated the same way as any other item in the browser, so they can be dragged and dropped within the browser (for example to copy a layer item to a geopackage file) or added to the current project through drag and drop or double click.

The context menu for an element in the Browser panel is opened by right-clicking on it.

For file system directory entries, the context menu offers the following:

• New ► to create in the selected entry a:

  • Directory…

  • GeoPackage…

  • ShapeFile…

• Add as a Favorite: favorite folders can be renamed (Rename favorite…) or removed (Remove favorite) any time.

• Hide from Browser: hidden folders can be toggled to visible from the Settings ► Options ► Data Sources ► Hidden browser paths setting

• Fast Scan this Directory

• Open Directory

• Open in Terminal

• Proprietăţi…

• Directory Properties…

For leaf entries that can act as layers in the project, the context menu will have supporting entries. For example, for non-database, non-service-based vector, raster and mesh data sources:

• Export Layer ► To File…

• Add Layer to Project

• Layer Properties

• Manage ► Rename „<name of file>”… or Delete „<name of file>”…

• Show in Files

• File Properties

In the Layer properties entry, you will find (similar to what you will find in the vector and raster layer properties once the layers have been added to the project):

• Metadata for the layer. Metadata groups: Information from provider (if possible, Path will be a hyperlink to the source), Identification, Extent, Access, Fields (for vector layers), Bands (for raster layers), Contacts, Links (for vector layers), References (for raster layers), History.

• A Preview panel

• The attribute table for vector sources (in the Attributes panel).

To add a layer to the project using the Browser:

1. Enable the Browser as described above. A browser tree with your file system, databases and web services is displayed. You may need to connect databases and web services before they appear (see dedicated sections).

2. Find the layer in the list.

3. Use the context menu, double-click its name, or drag-and-drop it into the map canvas. Your layer is now added to the Layers panel and can be viewed on the map canvas.

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   Open a QGIS project directly from the browser

   You can also open a QGIS project directly from the Browser panel by double-clicking its name or by drag-and-drop into the map canvas.

Once a file is loaded, you can zoom around it using the map navigation tools. To change the style of a layer, open the Layer Properties dialog by double-clicking on the layer name or by right-clicking on the name in the legend and choosing Properties from the context menu. See section Symbology Properties for more information on setting symbology for vector layers.

Right-clicking an item in the browser tree helps you to:

• for a file or a table, display its metadata or open it in your project. Tables can even be renamed, deleted or truncated.

• for a folder, bookmark it into your favourites or hide it from the browser tree. Hidden folders can be managed from the Settings ► Options ► Data Sources tab.

• manage your spatial bookmarks: bookmarks can be created, exported and imported as XML files.

• create a connection to a database or a web service.

• refresh, rename or delete a schema.

You can also import files into databases or copy tables from one schema/database to another with a simple drag-and-drop. There is a second browser panel available to avoid long scrolling while dragging. Just select the file and drag-and-drop from one panel to the other.

Fig. 15.2 Panourile Navigatorului QGIS, unul lângă altul

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Add layers to QGIS by simple drag-and-drop from your OS file browser

You can also add file(s) to the project by drag-and-dropping them from your operating system file browser to the Layers Panel or the map canvas.

15.1.2. The DB Manager

The DB Manager Plugin is another tool for integrating and managing spatial database formats supported by QGIS (PostGIS, SpatiaLite, GeoPackage, Oracle Spatial, MS SQL Server, Virtual layers). It can be activated from the Plugins ► Manage and Install Plugins… menu.

The ^{DB Manager} Plugin provides several features:

• connect to databases and display their structure and contents

• preview tables of databases

• add layers to the map canvas, either by double-clicking or drag-and-drop.

• add layers to a database from the QGIS Browser or from another database

• create SQL queries and add their output to the map canvas

• create virtual layers

More information on DB Manager capabilities is found in DB Manager Plugin.

Fig. 15.3 DB Manager dialog

15.1.3. Provider-based loading tools

Beside the Browser Panel and the DB Manager, the main tools provided by QGIS to add layers, you’ll also find tools that are specific to data providers.

Notă

Some external plugins also provide tools to open specific format files in QGIS.

15.1.3.1. Încărcarea unui strat dintr-un fișier

To load a layer from a file:

1. Open the layer type tab in the Data Source Manager dialog, ie click the ^{Open Data Source Manager} button (or press Ctrl+L) and enable the target tab or:

   • for vector data (like GML, ESRI Shapefile, Mapinfo and DXF layers): press Ctrl+Shift+V, select the Layer ► Add Layer ► Add Vector Layer menu option or click on the ^{Add Vector Layer} toolbar button.

     

     Fig. 15.4 Add Vector Layer Dialog

   • for raster data (like GeoTiff, MBTiles, GRIdded Binary and DWG layers): press Ctrl+Shift+R, select the Layer ► Add Layer ► Add Raster Layer menu option or click on the ^{Add Raster Layer} toolbar button.

     

     Fig. 15.5 Add Raster Layer Dialog

2. Check File source type

3. Click on the … ^Browse button

4. Navigate the file system and load a supported data source. More than one layer can be loaded at the same time by holding down the Ctrl key and clicking on multiple items in the dialog or holding down the Shift key to select a range of items by clicking on the first and last items in the range. Only formats that have been well tested appear in the formats filter. Other formats can be loaded by selecting All files (the top item in the pull-down menu).

5. Press Open to load the selected file into Data Source Manager dialog

   

   Fig. 15.6 Loading a Shapefile with open options

6. Press Add to load the file in QGIS and display them in the map view. Fig. 15.7 shows QGIS after loading the alaska.shp file.

   

   Fig. 15.7 QGIS with Shapefile of Alaska loaded

Notă

For loading vector and raster files the GDAL driver offers to define open actions. These will be shown when a file is selected. Options are described in detail on https://gdal.org/drivers/vector/, https://gdal.org/drivers/raster and if a file is selected in QGIS, a text with hyperlink will directly lead to the documentation of the selected file type.

Notă

Because some formats like MapInfo (e.g., .tab) or Autocad (.dxf) allow mixing different types of geometry in a single file, loading such datasets opens a dialog to select geometries to use in order to have one geometry per layer.

The ^{Add Vector Layer} and ^{Add Raster Layer} tabs allow loading of layers from source types other than File:

• You can load specific vector formats like ArcInfo Binary Coverage, UK. National Transfer Format, as well as the raw TIGER format of the US Census Bureau or OpenfileGDB. To do that, you select Directory as Source type. In this case, a directory can be selected in the dialog after pressing … ^Browse.

• With the Database source type you can select an existing database connection or create one to the selected database type. Some possible database types are ODBC, Esri Personal Geodatabase, MS SQL Server as well as PostgreSQL or MySQL .

  Pressing the New button opens the Create a New OGR Database Connection dialog whose parameters are among the ones you can find in Creating a stored Connection. Pressing Open lets you select from the available tables, for example of PostGIS enabled databases.

• The Protocol: HTTP(S), cloud, etc. source type opens data stored locally or on the network, either publicly accessible, or in private buckets of commercial cloud storage services. Supported protocol types are:

  • HTTP/HTTPS/FTP, with a URI and, if required, an authentication.

  • Cloud storage such as AWS S3, Google Cloud Storage, Microsoft Azure Blob, Alibaba OSS Cloud, Open Stack Swift Storage. You need to fill in the Bucket or container and the Object key.

  • service supporting OGC WFS 3 (still experimental), using GeoJSON or GEOJSON - Newline Delimited format or based on CouchDB database. A URI is required, with optional authentication.

  • For all vector source types it is possible to define the Encoding or to use the Automatic ► setting.

15.1.3.2. Loading a mesh layer

A mesh is an unstructured grid usually with temporal and other components. The spatial component contains a collection of vertices, edges and faces in 2D or 3D space. More information on mesh layers at Working with Mesh Data.

To add a mesh layer to QGIS:

1. Open the Data Source Manager dialog, either by selecting it from the Layer ► menu or clicking the ^{Open Data Source Manager} button.

2. Enable the Mesh tab on the left panel

3. Press the … ^Browse button to select the file. Various formats are supported.

4. Select the file and press Add. The layer will be added using the native mesh rendering.

5. If the selected file contains many mesh layers, then you’ll be prompted with a dialog to choose the sublayers to load. Do your selection and press OK and the layers are loaded with the native mesh rendering. It’s also possible to load them within a group.

Fig. 15.8 Mesh tab in Data Source Manager

15.1.3.3. Importarea unui fișier cu texte delimitate

Delimited text files (e.g. .txt, .csv, .dat, .wkt) can be loaded using the tools described above. This way, they will show up as simple tables. Sometimes, delimited text files can contain coordinates / geometries that you could want to visualize. This is what Add Delimited Text Layer is designed for.

1. Click the ^{Open Data Source Manager} icon to open the Data Source Manager dialog

2. Enable the Delimited Text tab

3. Select the delimited text file to import (e.g., qgis_sample_data/csv/elevp.csv) by clicking on the … ^Browse button.

4. In the Layer name field, provide the name to use for the layer in the project (e.g. Elevation).

5. Configure the settings to meet your dataset and needs, as explained below.

Fig. 15.9 Delimited Text Dialog

File format

Once the file is selected, QGIS attempts to parse the file with the most recently used delimiter, identifying fields and rows. To enable QGIS to correctly parse the file, it is important to select the right delimiter. You can specify a delimiter by choosing between:

• CSV (comma separated values) to use the comma character.

• Regular expression delimiter and enter text into the Expression field. For example, to change the delimiter to tab, use \t (this is used in regular expressions for the tab character).

• Custom delimiters, choosing among some predefined delimiters like comma, space, tab, semicolon, … .

Records and fields

Some other convenient options can be used for data recognition:

• Number of header lines to discard: convenient when you want to avoid the first lines in the file in the import, either because those are blank lines or with another formatting.

• First record has field names: values in the first line are used as field names, otherwise QGIS uses the field names field_1, field_2…

• Detect field types: automatically recognizes the field type. If unchecked then all attributes are treated as text fields.

• Decimal separator is comma: you can force decimal separator to be a comma.

• Trim fields: allows you to trim leading and trailing spaces from fields.

• Discard empty fields.

• Custom boolean literals: allows you to add a custom couple of string that will be detected as boolean values.

Field type detection

QGIS tries to detect the field types automatically (unless Detect field types is not checked) by examining the content of an optional sidecar CSVT file (see: GeoCSV specification) and by scanning the whole file to make sure that all values can actually be converted without errors, the fall-back field type is text.

The detected field type appears under the field name in sample data preview table and can be manually changed if necessary.

The following field types are supported:

• Boolean case-insensitive literal couples that are interpreted as boolean values are 1/0, true/false, t/f, yes/no

• Whole Number (integer)

• Whole Number (integer - 64 bit)

• Decimal Number: double precision floating point number

• Date

• Time

• Date and Time

• Text

Geometry definition

Once the file is parsed, set Geometry definition to

• Point coordinates and provide the X field, Y field, Z field (for 3-dimensional data) and M field (for the measurement dimension) if the layer is of point geometry type and contains such fields. If the coordinates are defined as degrees/minutes/seconds, activate the DMS coordinates checkbox. Provide the appropriate Geometry CRS using the ^{Select CRS} widget.

• Well known text (WKT) option if the spatial information is represented as WKT: select the Geometry field containing the WKT geometry and choose the approriate Geometry field or let QGIS auto-detect it. Provide the appropriate Geometry CRS using the ^{Select CRS} widget.

• If the file contains non-spatial data, activate No geometry (attribute only table) and it will be loaded as an ordinary table.

Layer settings

Additionally, you can enable:

• Use spatial index to improve the performance of displaying and spatially selecting features.

• Use subset index to improve performance of subset filters (when defined in the layer properties).

• Watch file to watch for changes to the file by other applications while QGIS is running.

At the end, click Add to add the layer to the map. In our example, a point layer named Elevation is added to the project and behaves like any other map layer in QGIS. This layer is the result of a query on the .csv source file (hence, linked to it) and would require to be saved in order to get a spatial layer on disk.

Sample Data

As you set the parser properties, the sample data preview updates regarding to the applied settings.

Also in the Sample Data Table it is possible to override the automatically determined column types.

15.1.3.4. Importarea unui fișier DXF sau DWG

DXF and DWG files can be added to QGIS by simple drag-and-drop from the Browser Panel. You will be prompted to select the sublayers you would like to add to the project. Layers are added with random style properties.

Notă

For DXF files containing several geometry types (point, line and/or polygon), the name of the layers will be generated as <filename.dxf> entities <geometry type>.

To keep the dxf/dwg file structure and its symbology in QGIS, you may want to use the dedicated Project ► Import/Export ► Import Layers from DWG/DXF… tool which allows you to:

1. import elements from the drawing file into a GeoPackage database.

2. add imported elements to the project.

In the DWG/DXF Import dialog, to import the drawing file contents:

1. Input the location of the Target package, i.e. the new GeoPackage file that will store the data. If an existing file is provided, then it will be overwritten.

2. Specify the coordinate reference system of the data in the drawing file.

3. Check Expand block references to import the blocks in the drawing file as normal elements.

4. Check Use curves to promote the imported layers to a curved geometry type.

5. Use the Import button to select the DWG/DXF file to use (one per geopackage). The GeoPackage database will be automatically populated with the drawing file content. Depending on the size of the file, this can take some time.

After the .dwg or .dxf data has been imported into the GeoPackage database, the frame in the lower half of the dialog is populated with the list of layers from the imported file. There you can select which layers to add to the QGIS project:

1. At the top, set a Group name to group the drawing files in the project.

2. Check layers to show: Each selected layer is added to an ad hoc group which contains vector layers for the point, line, label and area features of the drawing layer. The style of the layers will resemble the look they originally had in *CAD.

3. Choose if the layer should be visible at opening.

4. Checking the Merge layers option places all layers in a single group.

5. Press OK to open the layers in QGIS.

Fig. 15.10 Import dialog for DWG/DXF files

15.1.3.5. Importarea Vectorilor OpenStreetMap

The OpenStreetMap project is popular because in many countries no free geodata such as digital road maps are available. The objective of the OSM project is to create a free editable map of the world from GPS data, aerial photography and local knowledge. To support this objective, QGIS provides support for OSM data.

Using the Browser Panel, you can load an .osm file to the map canvas, in which case you’ll get a dialog to select sublayers based on the geometry type. The loaded layers will contain all the data of that geometry type in the .osm file, and keep the osm file data structure.

15.1.3.6. Straturile SpatiaLite

The first time you load data from a SpatiaLite database, begin by:

• clicking on the ^{Add SpatiaLite Layer} toolbar button

• selecting the Add SpatiaLite Layer… option from the Layer ► Add Layer menu

• or by typing Ctrl+Shift+L

This will bring up a window that will allow you either to connect to a SpatiaLite database already known to QGIS (which you choose from the drop-down menu) or to define a new connection to a new database. To define a new connection, click on New and use the file browser to point to your SpatiaLite database, which is a file with a .sqlite extension.

QGIS also supports editable views in SpatiaLite.

15.1.3.7. GPS

There are dozens of different file formats for storing GPS data. The format that QGIS uses is called GPX (GPS eXchange format), which is a standard interchange format that can contain any number of waypoints, routes and tracks in the same file.

Use the … ^Browse button to select the GPX file, then use the check boxes to select the feature types you want to load from that GPX file. Each feature type will be loaded in a separate layer.

More on GPS data manipulation at Lucrul cu datele GPS.

Fig. 15.11 Loading GPS Data dialog

15.1.3.8. GRASS

Working with GRASS vector data is described in section Integrarea GRASS GIS.

15.1.3.9. Database related tools

Creating a stored Connection

In order to read and write tables from a database format QGIS supports you have to create a connection to that database. While QGIS Browser Panel is the simplest and recommanded way to connect to and use databases, QGIS provides other tools to connect to each of them and load their tables:

• Add PostGIS Layer… or by typing Ctrl+Shift+D

• Add MS SQL Server Layer

• Add Oracle Spatial Layer… or by typing Ctrl+Shift+O

• Add SAP HANA Spatial Layer… or by typing Ctrl+Shift+G

These tools are accessible either from the Manage Layers Toolbar and the Layer ► Add Layer ► menu. Connecting to SpatiaLite database is described at Straturile SpatiaLite.

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Create connection to database from the QGIS Browser Panel

Selecting the corresponding database format in the Browser tree, right-clicking and choosing connect will provide you with the database connection dialog.

Most of the connection dialogs follow a common basis that will be described below using the PostgreSQL database tool as an example. For additional settings specific to other providers, you can find corresponding descriptions at:

• Connecting to MS SQL Server;

• Connecting to Oracle Spatial;

• Connecting to SAP HANA.

The first time you use a PostGIS data source, you must create a connection to a database that contains the data. Begin by clicking the appropriate button as exposed above, opening an Add PostGIS Table(s) dialog (see Fig. 15.14). To access the connection manager, click on the New button to display the Create a New PostGIS Connection dialog.

Fig. 15.12 Create a New PostGIS Connection Dialog

The parameters required for a PostGIS connection are explained below. For the other database types, see their differences at Particular Connection requirements.

• Name: A name for this connection. It can be the same as Database.

• Service: Service parameter to be used alternatively to hostname/port (and potentially database). This can be defined in pg_service.conf. Check the PostgreSQL Service connection file section for more details.

• Host: Name of the database host. This must be a resolvable host name such as would be used to open a TCP/IP connection or ping the host. If the database is on the same computer as QGIS, simply enter localhost here.

• Port: Port number the PostgreSQL database server listens on. The default port for PostGIS is 5432.

• Database: Name of the database.

• SSL mode: SSL encryption setup The following options are available:

  • Prefer (the default): I don’t care about encryption, but I wish to pay the overhead of encryption if the server supports it.

  • Require: I want my data to be encrypted, and I accept the overhead. I trust that the network will make sure I always connect to the server I want.

  • Verify CA: I want my data encrypted, and I accept the overhead. I want to be sure that I connect to a server that I trust.

  • Verify Full: I want my data encrypted, and I accept the overhead. I want to be sure that I connect to a server I trust, and that it’s the one I specify.

  • Allow: I don’t care about security, but I will pay the overhead of encryption if the server insists on it.

  • Disable: I don’t care about security, and I don’t want to pay the overhead of encryption.

• Authentication, basic.

  • User name: User name used to log in to the database.

  • Password: Password used with Username to connect to the database.

  You can save any or both of the User name and Password parameters, in which case they will be used by default each time you need to connect to this database. If not saved, you’ll be prompted to supply the credentials to connect to the database in next QGIS sessions. The connection parameters you entered are stored in a temporary internal cache and returned whenever a username/password for the same database is requested, until you end the current QGIS session.

  Atenționare

  QGIS User Settings and Security

  In the Authentication tab, saving username and password will keep unprotected credentials in the connection configuration. Those credentials will be visible if, for instance, you share the project file with someone. Therefore, it is advisable to save your credentials in an Authentication configuration instead (Configurations tab - See Sistem de Autentificare for more details) or in a service connection file (see PostgreSQL Service connection file for example).

• Authentication, configurations. Choose an authentication configuration. You can add configurations using the button. Choices are:

  • Basic authentication

  • PKI PKCS#12 authentication

  • PKI paths authentication

  • PKI stored identity certificate

Optionally, depending on the type of database, you can activate the following checkboxes:

• Only show layers in the layer registries

• Don’t resolve type of unrestricted columns (GEOMETRY)

• Only look in the «public» schema

• Also list tables with no geometry

• Use estimated table metadata

• Allow saving/loading QGIS projects in the database - more details here

• Allow saving/loading QGIS layer metadata in the database - more details here

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Use estimated table metadata to speed up operations

When initializing layers, various queries may be needed to establish the characteristics of the geometries stored in the database table. When the Use estimated table metadata option is checked, these queries examine only a sample of the rows and use the table statistics, rather than the entire table. This can drastically speed up operations on large datasets, but may result in incorrect characterization of layers (e.g. the feature count of filtered layers will not be accurately determined) and may even cause strange behaviour if columns that are supposed to be unique actually are not.

Once all parameters and options are set, you can test the connection by clicking the Test Connection button or apply it by clicking the OK button. From Add PostGIS Table(s), click now on Connect, and the dialog is filled with tables from the selected database (as shown in Fig. 15.14).

Particular Connection requirements

Because of database type particularities, provided options are not the same. Database specific options are described below.

PostgreSQL Service connection file

The service connection file allows PostgreSQL connection parameters to be associated with a single service name. That service name can then be specified by a client and the associated settings will be used.

It’s called .pg_service.conf under *nix systems (GNU/Linux, macOS etc.) and pg_service.conf on Windows.

The service file can look like this:

[water_service]
host=192.168.0.45
port=5433
dbname=gisdb
user=paul
password=paulspass

[wastewater_service]
host=dbserver.com
dbname=water
user=waterpass

Notă

There are two services in the above example: water_service and wastewater_service. You can use these to connect from QGIS, pgAdmin, etc. by specifying only the name of the service you want to connect to (without the enclosing brackets). If you want to use the service with psql you need to do something like export PGSERVICE=water_service before doing your psql commands.

You can find all the PostgreSQL parameters here

Notă

If you don’t want to save the passwords in the service file you can use the .pg_pass option.

On *nix operating systems (GNU/Linux, macOS etc.) you can save the .pg_service.conf file in the user’s home directory and PostgreSQL clients will automatically be aware of it. For example, if the logged user is web, .pg_service.conf should be saved in the /home/web/ directory in order to directly work (without specifying any other environment variables).

You can specify the location of the service file by creating a PGSERVICEFILE environment variable (e.g. run the export PGSERVICEFILE=/home/web/.pg_service.conf command under your *nix OS to temporarily set the PGSERVICEFILE variable)

You can also make the service file available system-wide (all users) either by placing the .pg_service.conf file in pg_config --sysconfdir or by adding the PGSYSCONFDIR environment variable to specify the directory containing the service file. If service definitions with the same name exist in the user and the system file, the user file takes precedence.

Atenționare

There are some caveats under Windows:

• The service file should be saved as pg_service.conf and not as .pg_service.conf.

• The service file should be saved in Unix format in order to work. One way to do it is to open it with Notepad++ and Edit ► EOL Conversion ► UNIX Format ► File save.

• You can add environmental variables in various ways; a tested one, known to work reliably, is Control Panel ► System and Security ► System ► Advanced system settings ► Environment Variables adding PGSERVICEFILE with the path - e.g. C:\Users\John\pg_service.conf

• After adding an environment variable you may also need to restart the computer.

Connecting to Oracle Spatial

The spatial features in Oracle Spatial aid users in managing geographic and location data in a native type within an Oracle database. In addition to some of the options in Creating a stored Connection, the connection dialog proposes:

• Database: SID or SERVICE_NAME of the Oracle instance;

• Port: Port number the Oracle database server listens on. The default port is 1521;

• Options: Oracle connection specific options (e.g. OCI_ATTR_PREFETCH_ROWS, OCI_ATTR_PREFETCH_MEMORY). The format of the options string is a semicolon separated list of option names or option=value pairs;

• Workspace: Workspace to switch to;

• Schema: Schema in which the data are stored

Optionally, you can activate the following checkboxes:

• Only look in metadata table: restricts the displayed tables to those that are in the all_sdo_geom_metadata view. This can speed up the initial display of spatial tables.

• Only look for user’s tables: when searching for spatial tables, restricts the search to tables that are owned by the user.

• Also list tables with no geometry: indicates that tables without geometry should also be listed by default.

• Use estimated table statistics for the layer metadata: when the layer is set up, various metadata are required for the Oracle table. This includes information such as the table row count, geometry type and spatial extents of the data in the geometry column. If the table contains a large number of rows, determining this metadata can be time-consuming. By activating this option, the following fast table metadata operations are done: Row count is determined from all_tables.num_rows. Table extents are always determined with the SDO_TUNE.EXTENTS_OF function, even if a layer filter is applied. Table geometry is determined from the first 100 non-null geometry rows in the table.

• Only existing geometry types: only lists the existing geometry types and don’t offer to add others.

• Include additional geometry attributes.

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Oracle Spatial Layers

Normally, an Oracle Spatial layer is defined by an entry in the USER_SDO_METADATA table.

To ensure that selection tools work correctly, it is recommended that your tables have a primary key.

Connecting to MS SQL Server

In addition to some of the options in Creating a stored Connection, creating a new MS SQL Server connection dialog proposes you to fill a Provider/DSN name. You can also display available databases.

Connecting to SAP HANA

Notă

You require the SAP HANA Client to connect to a SAP HANA database. You can download the SAP HANA Client for your platform at the SAP Development Tools website.

Fig. 15.13 Create a New SAP HANA Connection Dialog

The following parameters can be entered:

• Name: A name for this connection.

• Driver : The name of the HANA ODBC driver. It is HDBODBC if you are using 64-bit QGIS, HDBODBC32 if you are using 32-bit QGIS. The appropriate driver name is entered automatically.

• Driver : Either the name under which the SAP HANA ODBC driver has been registered in /etc/odbcinst.ini or the full path to the SAP HANA ODBC driver. The SAP HANA Client installer will install the ODBC driver to /usr/sap/hdbclient/libodbcHDB.so by default.

• Host: The name of the database host.

• Identifier: Identifies the instance to connect to on the host. This can be either Instance Number or Port Number. Instance numbers consist of two digits, port numbers are in the range from 1 to 65,535.

• Mode: Specifies the mode in which the SAP HANA instance runs. This setting is only taken into account if Identifier is set to Instance Number. If the database hosts multiple containers, you can either connect to a tenant with the name given at Tenant database or you can connect to the system database.

• Schema: This parameter is optional. If a schema name is given, QGIS will only search for data in that schema. If this field is left blank, QGIS will search for data in all schemas.

• Authentication ► Basic.

  • User name: User name used to connect to the database.

  • Password: Password used to connect to the database.

• SSL Settings

  • Enable TLS/SSL encryption: Enables TLS 1.1 - TLS1.2 encryption. The server will choose the highest available.

  • Provider: Specifies the cryptographic library provider used for SSL communication. sapcrypto should work on all platforms, openssl should work on , mscrypto should work on and commoncrypto requires CommonCryptoLib to be installed.

  • Validate SSL certificate: If checked, the SSL certificate will be validated using the truststore given in Trust store file with public key.

  • Override hostname in certificate: Specifies the host name used to verify server’s identity. The host name specified here verifies the identity of the server instead of the host name with which the connection was established. If you specify * as the host name, then the server’s host name is not validated. Other wildcards are not permitted.

  • Keystore file with private key: Currently ignored. This parameter might allow to authenticate via certificate instead via user and password in future.

  • Trust store file with public key: Specifies the path to a trust store file that contains the server’s public certificates if using OpenSSL. Typically, the trust store contains the root certificate or the certificate of the certification authority that signed the server’s public certificates. If you are using the cryptographic library CommonCryptoLib or msCrypto, then leave this property empty.

• Only look for user’s tables: If checked, QGIS searches only for tables and views that are owned by the user that connects to the database.

• Also list tables with no geometries: If checked, QGIS searches also for tables and views that do not contain a spatial column.

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Connecting to SAP HANA Cloud

If you’d like to connect to an SAP HANA Cloud instance, you usually must set Port Number to 443 and check Enable TLS/SSL encryption.

Încărcarea unui Strat al unei Baze de date

Once you have one or more connections defined to a database (see section Creating a stored Connection), you can load layers from it. Of course, this requires that data are available. See section Importing Data into PostgreSQL for a discussion on importing data into a PostGIS database.

To load a layer from a database, you can perform the following steps:

1. Open the „Add <database> table(s)” dialog (see Creating a stored Connection).

2. Choose the connection from the drop-down list and click Connect.

3. Select or unselect Also list tables with no geometry.

4. Optionally, use some Search Options to reduce the list of tables to those matching your search. You can also set this option before you hit the Connect button, speeding up the database fetching.

5. Find the layer(s) you wish to add in the list of available layers.

6. Select it by clicking on it. You can select multiple layers by holding down the Shift or Ctrl key while clicking.

7. If applicable, use the Set Filter button (or double-click the layer) to start the Query Builder dialog (see section Constructorul de Interogări) and define which features to load from the selected layer. The filter expression appears in the sql column. This restriction can be removed or edited in the Layer Properties ► General ► Provider Feature Filter frame.

8. The checkbox in the Select at id column that is activated by default gets the feature ids without the attributes and generally speeds up the data loading.

9. Click on the Add button to add the layer to the map.

Fig. 15.14 Add PostGIS Table(s) Dialog

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Use the Browser Panel to speed up loading of database table(s)

Adding DB tables from the Data Source Manager may sometimes be time consuming as QGIS fetches statistics and properties (e.g. geometry type and field, CRS, number of features) for each table beforehand. To avoid this, once the connection is set, it is better to use the Browser Panel or the DB Manager to drag and drop the database tables into the map canvas.

15.1.4. The Layer Metadata Search Panel

The layer metadata search panel allows to browse layers metadata from registered metadata providers and add them to the project.

The list can be filtered by text, by current project and by map canvas extent.

The sources of metadata are implemented through a layer metadata provider system that can be extended by plugins.

QGIS provides out of the box the layer metadata providers that retrieve the metadata from the connections that allow for metadata storage (for more details save metadata to the database).

Fig. 15.15 Layer Metadata Search Panel

15.1.5. QGIS Custom formats

QGIS proposes two custom formats:

• Temporary Scratch Layer: a memory layer that is bound to the project (see Creating a new Temporary Scratch Layer for more information)

• Virtual Layers: a layer resulting from a query on other layer(s) (see Creating virtual layers for more information)

15.1.6. QLR - QGIS Layer Definition File

Layer definitions can be saved as a Layer Definition File (QLR - .qlr) using Export ► Save As Layer Definition File… in the layer context menu.

The QLR format makes it possible to share „complete” QGIS layers with other QGIS users. QLR files contain links to the data sources and all the QGIS style information necessary to style the layer.

QLR files are shown in the Browser Panel and can be used to add layers (with their saved styles) to the Layers Panel. You can also drag and drop QLR files from the system file manager into the map canvas.

15.1.7. Connecting to web services

With QGIS you can get access to different types of OGC web services (WM(T)S, WFS(-T), WCS, CSW, …). Thanks to QGIS Server, you can also publish such services. Ghid/Manual QGIS Server contains descriptions of these capabilities.

15.1.7.1. Using Vector Tiles services

Vector Tile services can be added via the Vector Tiles tab of the Data Source Manager dialog or the contextual menu of the Vector Tiles entry in the Browser panel. Services can be either a New Generic Connection… or a New ArcGIS Vector Tile Service Connection….

You set up a service by adding:

• a Name

• the URL: of the type http://example.com/{z}/{x}/{y}.pbf for generic services and http://example.com/arcgis/rest/services/Layer/VectorTileServer for ArcGIS based services. The service must provide tiles in .pbf format.

• the Min. Zoom Level and the Max. Zoom Level. Vector Tiles have a pyramid structure. By using these options you have the opportunity to individually generate layers from the tile pyramid. These layers will then be used to render the Vector Tile in QGIS.

  For Mercator projection (used by OpenStreetMap Vector Tiles) Zoom Level 0 represents the whole world at a scale of 1:500.000.000. Zoom Level 14 represents the scale 1:35.000.

• a Style URL: a URL to a MapBox GL JSON style configuration. If provided, then that style will be applied whenever the layers from the connection are added to QGIS. In the case of Arcgis vector tile service connections, the URL overrides the default style configuration specified in the server configuration.

• the authentication configuration if necessary

• a Referer

Fig. 15.16 shows the dialog with the MapTiler planet Vector Tiles service configuration.

Fig. 15.16 Vector Tiles - Maptiler Planet configuration

Configurations can be saved to .XML file (Save Connections) through the Vector Tiles entry in Data Source Manager dialog or its context menu in the Browser panel. Likewise, they can be added from a file (Load Connections).

Once a connection to a vector tile service is set, it’s possible to:

• Edit the vector tile connection settings

• Remove the connection

• From the Browser panel, right-click over the entry and you can also:

  • Add layer to project: a double-click also adds the layer

  • View the Layer Properties… and get access to metadata and a preview of the data provided by the service. More settings are available when the layer has been loaded into the project.

15.1.7.2. Using XYZ Tile services

XYZ Tile services can be added via the XYZ tab of the Data Source Manager dialog or the contextual menu of the XYZ Tiles entry in the Browser panel. Press New (respectively New Connection) and provide:

• a Name

• the URL

• the authentication configuration if necessary

• the Min. Zoom level and Max. Zoom level

• a Referer

• the Tile Resolution: possible values are Unknown (not scaled), Standard (256x256 / 96DPI) and High (512x512 / 192DPI)

• Interpretation: converts WMTS/XYZ raster datasets to a raster layer of single band float type following a predefined encoding scheme. Supported schemes are Default (no conversion is done), MapTiler Terrain RGB and Terrarium Terrain RGB. The selected converter will translate the RGB source values to float values for each pixel. Once loaded, the layer will be presented as a single band floating point raster layer, ready for styling using QGIS usual raster renderers.

By default, QGIS provides some default and ready-to-use XYZ Tiles services:

• Mapzen Global Terrain, allowing an immediate access to global DEM source for the projects. More details and resources at https://registry.opendata.aws/terrain-tiles/

• OpenStreetMap to access the world 2D map. Fig. 15.17 shows the dialog with the OpenStreetMap XYZ Tile service configuration.

  

  Fig. 15.17 XYZ Tiles - OpenStreetMap configuration

Configurations can be saved to .XML file (Save Connections) through the XYZ Tiles entry in Data Source Manager dialog or its context menu in the Browser panel. Likewise, they can be added from a file (Load Connections).

The XML file for OpenStreetMap looks like this:

<!DOCTYPE connections>
<qgsXYZTilesConnections version="1.0">
  <xyztiles url="https://tile.openstreetmap.org/{z}/{x}/{y}.png"
   zmin="0" zmax="19" tilePixelRatio="0" password="" name="OpenStreetMap"
   username="" authcfg="" referer=""/>
</qgsXYZTilesConnections>

Once a connection to a XYZ tile service is set, it’s possible to:

• Edit the XYZ connection settings

• Remove the connection

• From the Browser panel, right-click over the entry and you can also:

  • Export layer… ► To File, saving it as a raster

  • Add layer to project: a double-click also adds the layer

  • View the Layer Properties… and get access to metadata and a preview of the data provided by the service. More settings are available when the layer has been loaded into the project.

Exemple de servicii pentru Plăcuțe XYZ:

• OpenStreetMap Monochrome: URL: http://tiles.wmflabs.org/bw-mapnik/{z}/{x}/{y}.png, Min. Zoom Level: 0, Max. Zoom Level: 19.

• Google Maps: URL: https://mt1.google.com/vt/lyrs=m&x={x}&y={y}&z={z}, Min. Zoom Level: 0, Max. Zoom Level: 19.

• Open Weather Map Temperature: URL: http://tile.openweathermap.org/map/temp_new/{z}/{x}/{y}.png?appid={api_key} Min. Zoom Level: 0, Max. Zoom Level: 19.

15.1.7.3. Using ArcGIS REST Servers

ArcGIS REST Servers can be added via the ArcGIS REST Server tab of the Data Source Manager dialog or the contextual menu of the ArcGIS REST Servers entry in the Browser panel. Press New (respectively New Connection) and provide:

• a Name

• the URL

• a Community endpoint URL

• a Content endpoint URL

• the authentication configuration if necessary

• a Referer

Notă

ArcGIS Feature Service connections which have their corresponding Portal endpoint URLS set can be explored by content groups in the browser panel.

If a connection has the Portal endpoints set, then expanding out the connection in the browser will show a “Groups” and “Services” folder, instead of the full list of services usually shown. Expanding out the groups folder will show a list of all content groups that the user is a member of, each of which can be expanded to show the service items belonging to that group.

Configurations can be saved to .XML file (Save Connections) through the ArcGIS REST Server entry in Data Source Manager dialog. Likewise, they can be added from a file (Load Connections).

Once a connection to an ArcGIS REST Server is set, it’s possible to:

• Edit the ArcGIS REST Server connection settings

• Remove the connection

• Refresh the connection

• use a filter for the available layers

• choose from a list of available layers with the option to Only request features overlapping the current view extent

• From the Browser panel, right-click over the connection entry and you can:

  • Refresh

  • Edit connection…

  • Remove connection…

  • View Service Info which will open the default web browser and display the Service Info.

• Right-click over the layer entry and you can also:

  • View Service Info which will open the default web browser and display the Service Info.

  • Export layer… ► To File

  • Add layer to project: a double-click also adds the layer

  • View the Layer Properties… and get access to metadata and a preview of the data provided by the service. More settings are available when the layer has been loaded into the project.