QGIS

https://docs.qgis.org/3.44/en/docs
Admin
QGIS is a free and open source community-driven Geographic Information System (GIS) software for...
Tokens:1,116,521
Snippets:8,087
Trust Score:10
Update:2 weeks ago
Show doc for...
Tokens:
Raw
### spawn-fcgi setup for QGIS Server

Source: https://docs.qgis.org/3.44/en/docs/server_manual/getting_started.html

Steps to set up QGIS Server with spawn-fcgi: install the package, add the NGINX location block, restart NGINX, and manually start the FastCGI process. The server is then available at http://qgis.demo/qgisserver.

```bash
apt install spawn-fcgi

```

```nginx
location /qgisserver {
    gzip           off;
    include        fastcgi_params;
    fastcgi_pass   unix:/var/run/qgisserver.socket;
}

```

```bash
systemctl restart nginx

```

```bash
spawn-fcgi -s /var/run/qgisserver.socket \
                -U www-data -G www-data -n \
                /usr/lib/cgi-bin/qgis_mapserv.fcgi

```

--------------------------------

### Sample output from TaskFromFunction

Source: https://docs.qgis.org/3.44/en/docs/pyqgis_developer_cookbook/tasks.html

Example output from running the task-from-function example, showing task start and completion messages.

```text
RandomIntegerSumTask(0): Started task "waste cpu subtask short"
RandomTaskFromFunction(0): Started task Waste cpu 1
RandomTaskFromFunction(0): Started task Waste cpu 2
RandomTaskFromFunction(0): Task Waste cpu 2 completed
RandomTotal: 23263 ( with 100 iterations)
RandomTaskFromFunction(0): Task Waste cpu 1 completed
RandomTotal: 25044 ( with 100 iterations)
```

--------------------------------

### Expected output of kubectl get pods,services,deployment

Source: https://docs.qgis.org/3.44/en/docs/server_manual/containerized_deployment.html

Example output from kubectl get pods,services,deployment showing the expected running pods, services, and deployments after applying the manifests.

```text
NAME                               READY   STATUS    RESTARTS   AGE
pod/qgis-nginx-54845ff6f6-8skp9    1/1     Running   0          27m
pod/qgis-server-75df8ddd89-c7t7s   1/1     Running   0          27m

NAME                       TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)        AGE
service/Kubernetes         ClusterIP   10.152.183.1     <none>        443/TCP        5h51m
service/qgis-exec-server   ClusterIP   10.152.183.218   <none>        5555/TCP       35m
service/qgis-nginx         NodePort    10.152.183.234   <none>        80:30080/TCP   27m
service/qgis-server        ClusterIP   10.152.183.132   <none>        5555/TCP       27m

NAME                          READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/qgis-nginx    1/1     1            1           27m
deployment.apps/qgis-server   1/1     1            1           27m

```

--------------------------------

### fcgiwrap setup for QGIS Server

Source: https://docs.qgis.org/3.44/en/docs/server_manual/getting_started.html

Steps to set up QGIS Server with fcgiwrap: install the package, add the NGINX location block that uses the fcgiwrap socket and sets SCRIPT_FILENAME, then restart NGINX and fcgiwrap. The server is available at http://qgis.demo/qgisserver.

```bash
apt install fcgiwrap

```

```nginx
1 location /qgisserver {
2     gzip           off;
3     include        fastcgi_params;
4     fastcgi_pass   unix:/var/run/fcgiwrap.socket;
5     fastcgi_param  SCRIPT_FILENAME /usr/lib/cgi-bin/qgis_mapserv.fcgi;
6 }

```

```bash
systemctl restart nginx
systemctl restart fcgiwrap

```

--------------------------------

### RESTful WMTS Service URL Example

Source: https://docs.qgis.org/3.44/en/docs/user_manual/working_with_ogc/ogc_client_support.html

Example RESTful WMTS address for an Austrian basemap. Access it in QGIS by adding the address in the URL field of the WMS setup.

```text
https://maps.wien.gv.at/basemap/1.0.0/WMTSCapabilities.xml
```

--------------------------------

### Test QGIS Server installation

Source: https://docs.qgis.org/3.44/en/docs/server_manual/getting_started.html

Run this command to test the QGIS Server installation. If the server is correctly installed, you will see the output shown in the next snippet.

```bash
/usr/lib/cgi-bin/qgis_mapserv.fcgi
```

--------------------------------

### Example action call using URL with expression

Source: https://docs.qgis.org/3.44/en/docs/user_manual/working_with_vector/vector_properties.html

An example of an action call that constructs a URL with an expression. The expression uses the map() and url_encode() functions to build a query string. This is shown as an example of how to define an action.

```text
http://localhost:8000?/[% url_encode(map('file', 'index.php')) %]

```

--------------------------------

### Install GPSD

Source: https://docs.qgis.org/3.44/en/docs/user_manual/working_with_gps/live_GPS_tracking.html

Install GPSD on Ubuntu/Mint GNU/Linux as a middleware for connecting GPS devices.

```bash
sudo apt install gpsd

```

--------------------------------

### WMTS KVP Service URL Example

Source: https://docs.qgis.org/3.44/en/docs/user_manual/working_with_ogc/ogc_client_support.html

Example URL for a WMTS KVP service. The topo2 layer in this WMTS works nicely for testing.

```text
https://opencache.statkart.no/gatekeeper/gk/gk.open_wmts?service=WMTS&request=GetCapabilities
```

--------------------------------

### QGIS Attribute Action Examples

Source: https://docs.qgis.org/3.44/en/docs/user_manual/working_with_vector/vector_properties.html

Example actions for the QGIS attribute action feature. The first uses the %name field placeholder, the second uses %% for the selected field value, and the third provides a full path to the konqueror executable.

```text
konqueror https://www.google.com/search?q=%name
```

```text
konqueror https://www.google.com/search?q=%%
```

```text
/opt/kde3/bin/konqueror https://www.google.com/search?q=%name
```

--------------------------------

### Example output of the bash action

Source: https://docs.qgis.org/3.44/en/docs/user_manual/working_with_vector/vector_properties.html

This is the expected content of the output file after running the bash action on selected localities. It shows the exported field values.

```text
Acacia mearnsii -34.0800000000 150.0800000000
Acacia mearnsii -34.9000000000 150.1200000000
Acacia mearnsii -35.2200000000 149.9300000000
Acacia mearnsii -32.2700000000 150.4100000000
```

--------------------------------

### Database schema for polymorphic relation example

Source: https://docs.qgis.org/3.44/en/docs/user_manual/working_with_vector/joins_relations.html

SQL schema for the polymorphic relation example: creates the park schema and the animals, plants, and documents tables. The documents table has referenced_layer and referenced_id fields used as the referencing (child) layer, while animals and plants are referenced (parent) layers with fid as primary key.

```sql
CREATE SCHEMA park;

CREATE TABLE park.animals
(
   fid serial NOT NULL,
   geom geometry(Point, 4326) NOT NULL,
   animal_species text NOT NULL,
   CONSTRAINT animals_pkey PRIMARY KEY (fid)
);

CREATE INDEX animals_geom_idx ON park.animals USING gist (geom);

CREATE TABLE park.plants
(
   fid serial NOT NULL,
   geom geometry(Point, 4326) NOT NULL,
   plant_species text NOT NULL,
   CONSTRAINT plants_pkey PRIMARY KEY (fid)
);

CREATE INDEX plants_geom_idx ON park.plants USING gist (geom);

CREATE TABLE park.documents
(
   fid serial NOT NULL,
   referenced_layer text NOT NULL,
   referenced_id integer NOT NULL,
   image_filename text NOT NULL,
   CONSTRAINT documents_pkey PRIMARY KEY (fid)
);
```

--------------------------------

### GPSBabel device download command with keyword substitution

Source: https://docs.qgis.org/3.44/en/docs/user_manual/working_with_gps/plugins_gps.html

Example command for a GPSBabel device type. QGIS replaces %type, %in, and %out with actual values when running the command. For waypoint download from /dev/ttyS0 to output.gpx, it becomes: gpsbabel -w -i garmin -o gpx /dev/ttyS0 output.gpx.

```bash
gpsbabel %type -i garmin -o gpx %in %out
```

```bash
gpsbabel -w -i garmin -o gpx /dev/ttyS0 output.gpx
```

--------------------------------

### SVG with dynamic parameters

Source: https://docs.qgis.org/3.44/en/docs/user_manual/style_library/symbol_selector.html

SVG example showing free parametrization using param(param_name) as attribute values or node text. Parameters can be defined as expressions in the Dynamic SVG parameters table.

```svg
<g stroke-width=".265" text-anchor="middle" alignment-baseline="param(align)">
  <text x="98" y="147.5" font-size="6px">param(text1)</text>
  <text x="98" y="156.3" font-size="4.5px">param(text2)</text>
</g>
```

--------------------------------

### Calculate area of polygon layer

Source: https://docs.qgis.org/3.44/en/docs/user_manual/processing_algs/qgis/vectortable.html

Example formula for the 'Formula' parameter to calculate the area of an input polygon layer. Uses the geometry's area() method.

```python
value = $geom.area()
```

--------------------------------

### MapServer GetFeatureInfo GML configuration

Source: https://docs.qgis.org/3.44/en/docs/user_manual/working_with_ogc/ogc_client_support.html

Example MapServer configuration to enable GetFeatureInfo responses in GML format for the QGIS Identify tool. It defines layer metadata fields and geometry, then shows two format options: basic (no XSD) and OGR-based (multipart with XSD).

```mapfile
# in layer METADATA add which fields should be included and define geometry (example):

"gml_include_items"   "all"
"ows_geometries"      "mygeom"
"ows_mygeom_type"     "polygon"

# Then there are two possibilities/formats available, see a) and b):

# a) basic (output is generated by Mapserver and does not contain XSD)
# in WEB METADATA define formats (example):
"wms_getfeatureinfo_formatlist" "application/vnd.ogc.gml,text/html"

# b) using OGR (output is generated by OGR, it is sent as multipart and contains XSD)
# in MAP define OUTPUTFORMAT (example):
OUTPUTFORMAT
    NAME "OGRGML"
    MIMETYPE "ogr/gml"
    DRIVER "OGR/GML"
    FORMATOPTION "FORM=multipart"
END

# in WEB METADATA define formats (example):
"wms_getfeatureinfo_formatlist" "OGRGML,text/html"
```

--------------------------------

### QGIS expression with HTML formatting

Source: https://docs.qgis.org/3.44/en/docs/user_manual/style_library/label_settings.html

Example of a QGIS expression that uses HTML formatting to apply different colors and underline to the same label. Uses format() function with HTML span tags.

```qgis
format(
  '<span style="color:blue">%1</span> ( <span style="color:red"><u>%2 ft</u></span> )',
  title( lower( "Name" ) ),
  round($length)
)
```

--------------------------------

### Python action: add raster layer to project

Source: https://docs.qgis.org/3.44/en/docs/user_manual/working_with_vector/vector_properties.html

Python action that adds a raster layer (a TIF image in this example) to the project. The file path and layer name are data-driven, using the 'filename' and 'layername' attribute column values from the vector layer where the action was created.

```python
qgis.utils.iface.addRasterLayer('/yourpath/[% "filename" %].tif',
  '[% "layername" %]')
```

--------------------------------

### Download sample QGIS project

Source: https://docs.qgis.org/3.44/en/docs/server_manual/getting_started.html

Commands to download and set up a sample QGIS project from the Training demo data. Creates a projects directory, downloads the release_3.22 archive, and moves the world.qgs and naturalearth.sqlite files into it.

```bash
mkdir /home/qgis/projects/
cd /home/qgis/projects/
wget https://github.com/qgis/QGIS-Training-Data/archive/release_3.22.zip
unzip release_3.22.zip
mv QGIS-Training-Data-release_3.22/exercise_data/qgis-server-tutorial-data/world.qgs .
mv QGIS-Training-Data-release_3.22/exercise_data/qgis-server-tutorial-data/naturalearth.sqlite .
```

--------------------------------

### Get field values with QgsVectorLayerUtils.getValues()

Source: https://docs.qgis.org/3.44/en/docs/pyqgis_developer_cookbook/vector.html

Gets the values of a field or expression using QgsVectorLayerUtils.getValues(). The example selects only the first feature to shorten the output; the printed result is shown.

```python
vlayer = QgsVectorLayer("testdata/data/data.gpkg|layername=airports", "Airports layer", "ogr")
# select only the first feature to make the output shorter
vlayer.selectByIds([1])
val = QgsVectorLayerUtils.getValues(vlayer, "NAME", selectedOnly=True)
print(val)

```

```output
(['Sahnewal'], True)

```

--------------------------------

### Run native:buffer with parameters

Source: https://docs.qgis.org/3.44/en/docs/user_manual/processing/console.html

Concrete example of running the native:buffer algorithm with a dictionary of parameters. The keys correspond to the parameters listed by algorithmHelp(), and the values are the chosen inputs and output path.

```python
1 >>> processing.run("native:buffer", {'INPUT': '/data/lines.shp',
2               'DISTANCE': 100.0,
3               'SEGMENTS': 10,
4               'DISSOLVE': True,
5               'END_CAP_STYLE': 0,
6               'JOIN_STYLE': 0,
7               'MITER_LIMIT': 10,
8               'OUTPUT': '/data/buffers.shp'})

```

--------------------------------

### Start QGIS with data files

Source: https://docs.qgis.org/3.44/en/docs/user_manual/introduction/qgis_configuration.html

Starts QGIS with a vector layer and a raster file set to load on startup. Assumes you are in the `qgis_sample_data` directory.

```bash
qgis ./raster/landcover.img ./gml/lakes.gml
```
Tokens:
Raw