Questions tagged [qgis-3]
for questions specific to the 3.x series of QGIS.
1,232 questions
0
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0answers
7 views
Detecting checking/unchecking of rules in a rule-based rendering using PyQgis [on hold]
Is it possible to programmatically detect checking/unchecking changes of a rule in a rule-based rendering ? I found no indication of existing signals ..
I got lost reading QgsVectorLayerRenderer ...
1
vote
1answer
35 views
Efficiently query two properties QGIS spatialite
I have a simple query that involves two steps:
non-spatial criteria (should be super-fast)
spatial criteria (which is really slow)
I would like to run the spatial query only on the filtered layer (...
2
votes
0answers
9 views
QGIS Model Processing Raster Calculator Error
I am using "raster calculator" tool of the saga in my model. The tool correctly executes raster operation like "a * 2" in value formula option but the same expression is not executed pre-calculated ...
1
vote
1answer
31 views
Can we call a single attribute entry (=one row) “a feature” of the Layer?
For the single layer(for example Airport layer) there are many entries in the attribute table.Can we call single attribute row entry a feature of the Airport Layer? Can somebody give clear view of ...
4
votes
1answer
61 views
Deleting features in PyQGIS?
I am comparing geometries of input layer and output layer features. I want to delete features in output layers which has equal geometry to input feature. I am using following code to do that.
for ...
3
votes
1answer
23 views
Specifying snap raster in QGIS?
I am deploying QGIS 3.6 on Windows 10.
Using the Raster > Projections > Warp (Reproject) tool, I need to reproject a single-band, float32, GeoTIFF DEM from EPSG:3413 to EPSG:3857.
The output ...
1
vote
1answer
39 views
Points Layer to Distance Matrix QGIS 3.6 - Noosa
I'm trying to calculate a sample distance matrix from four points in the BNG CRS:
Using Vector-> Analysis Tools -> Distance Matrix, I get:
Input point layer is a MultiPoint layer - first convert to ...
1
vote
0answers
24 views
Adding new field and calculating in Pyqgis
I'm trying to write a plugin using QGIS 3.4. What I want to achieve is an excel-style calculation where I can create a new field (field2) and calculate the difference between current and previous row ...
0
votes
0answers
14 views
3D Visualization Error
I am having an issue utilizing 3D Visualization. When I access New 3D Map View, the map that shows up is a 2D representation. Seeing this, I navigate to the 3D configuration tab (represented by a ...
2
votes
0answers
31 views
Mouse pointer always “in work”
I used QGIS 3.2 Bonn and suddenly, and I don´t know why, the mouse pointer never stops rotating as the project is in work. It is still possible to click and select things like it is possible with the ...
-2
votes
0answers
40 views
Migration flow maps with QGIS 3.6 [on hold]
I want to make flow maps with QGIS 3.6 but without using the FlowMapper (because it doesn't work)
2
votes
0answers
26 views
Create filter expression by selected elements?
Is it possible to automatically create a filter expression for the Query Builder by selected elements?
1
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0answers
22 views
Remove and reload raster layer from previously created QgsRasterLayer object
I have created a QgsRasterLayer object using:
lyr=QgsRasterLayer(url,'lyr_name')
and the layer is displayed by:
QgsProject.instance().addMapLayer(lyr)
Now when this layer is removed through:
...
1
vote
1answer
31 views
Showing only one feature per Report page in QGIS 3
The gift of Reports in QGIS is a massive step in the right direction. I have set up a department template for my team to use and it looks great!
Right now, I am attempting to setup a report that will ...
4
votes
0answers
32 views
How to use Layer Parameter variables in Field Calculator within a Model?
If I define a Vector Layer as an input parameter to a QGIS model, then the parameter name is exposed as a variable in a Field Calculator within the model, however I am unable to use this variable as I ...
1
vote
1answer
45 views
How to integrate QGIS 3.4 with the DE theme
I just got the upgrade to QGIS 3.4 from the ubuntugis-unstable PPA. One thing that immediately stands in this version is that it ignore the DE theme, instead yielding an unhealthy white-based theme. ...
-4
votes
0answers
31 views
Difference between definitions “feature” vs. “layer” [duplicate]
What is the difference between the two definitions "feature" vs "layer" by means of GIS?
Especially in QGIS (PyQGIS) is there any difference to say "feature" or "layer"?
For example, I have the ...
2
votes
0answers
34 views
How to get raster layer metadata in python for QGIS 3.6? [closed]
I am loading imagery as raster layer through a URL. I need to store its metadata as JSON string in db for future reference.
I tried getting the metadata via layer.metadata() and then tried to get ...
1
vote
1answer
13 views
Rule for labeling ways not being part of OSM relation in QGIS
A brief overview of what I want to achieve: Create a map showing all cross-country ski trails in a specific region with some customizations/styling on them.
The data come from OpenStreetMap ...
1
vote
2answers
38 views
QGIS 3.4 / QgsVectorLayer()
I tried to use QgsProject.instance().addMapLayer(layer) on QGIS 3.4 but I didn't succeed.
Example:
layer = QgsVectorLayer(r'C:\CURSO_PYQGIS\CAPAS\urbano.shp','urbano','ogr ')
QgsProject.instance()....
3
votes
0answers
39 views
Finding path between points on limited road network
I am struggling to find a path between health facilities in Madagascar.
I think that because the road network (from OpenStreetMap) is limited, the functions in QGIS, such as v.net.distance and ...
3
votes
1answer
32 views
Issue converting CSV files to point shapefiles using pyqgis - QGIS 3
I have hit a snag using pyqgis in QGIS 3. I want to convert a set of CSVs (20 total) into point shapefiles but I am struggling with just the single CSV case. My code is based on this blogpost (https://...
1
vote
2answers
46 views
QGIS SAGA functions failing “… following layers not correctly generated. …”
I've been having an issue with the SAGA functions for a while now, I believe since upgrading to one of the early 3.x versions. No matter which function I use they all fail with the same error (...
0
votes
1answer
27 views
How do I make a map's background transparent in a layout?
I am trying to add an overview map to my layout. The main map is projected while the overview map is a 'globe' (image below). I want to make the white part of the overview map transparent.
I have ...
1
vote
2answers
44 views
Adding tile layer via PyQGIS
Any idea how to add a tile layer (XYZ-Layer) using PyQGIS 101 to a map?
Something like osmLayer = QgsXYZLayer(uri.uri(), "OpenStreetMap", "XYZ")
"XYZ" is a raw guess.
Running QGIS 3.6.0
0
votes
0answers
17 views
QGIS Heat Map output not correct
Fairly new to QGIS here. I'm having trouble creating a heat map in QGIS3 from a set of points.
I've followed what others have done online (e.g.: https://www.youtube.com/watch?v=o9Gqrr5cYrY) but in my ...
1
vote
0answers
16 views
pyqgis 3:how to identify partial intersections between a buffer (polygon) layer and pipe (line) layer?
I have a drains layer (polygon) around which I have created buffers of varying distances. I want to find the intersection between the different buffer layers and pipes (line) layer and accordingly ...
-2
votes
0answers
24 views
Listing all layers of legends using PyQGIS? [duplicate]
I want to list all of the available layers of layer panel in console using PyQGIS.Can you please suggest class and methods to do so.
1
vote
1answer
52 views
QGIS 3 Processing Script refer to input layer
I'm new to Python and trying to figure out how to write my first Processing Script using QGIS 3.6 on Windows 10.
I'm using the default template provided in QGIS 3 (Toolbox > New script from template)....
-1
votes
0answers
18 views
Pyqgis code for Calculating Proportion area of Polygon inside another Polygon Layer [closed]
I have two Layer in my project 1) VorLayer and 2) WardBound Lyr. Both Layer are Polygon.The WardBoundLyr are represented using dark black border in below image.
While the thin black ones are VorLayer....
1
vote
1answer
45 views
Resolving blanks when calculating attributes for almost 2 million polygons in QGIS?
I am starting with this Hazard Parcel Exposure dataset from the Metropolitan Transportation Commission which I downloaded as a shapefile.
http://opendata.mtc.ca.gov/datasets/parcel-hazard-exposure
...
1
vote
1answer
59 views
Generating map tiles with QGIS 3.6?
Similar to this rather dated question, is there a way to generate map tiles on QGIS 3.6? The plugins linked from that question only support QGIS 2.x. I wonder if things have changed in QGIS 3.x ...
3
votes
0answers
45 views
Automatisation of isochrone map creation in QGIS 3
I need to measure the area of isochrones for a big number of points, for different time thresholds and for different means of transport.
I've been using the plugin isochrones in OSM tools with QGIS 3....
0
votes
1answer
25 views
PyQGIS3 retrieving points from a shortestpath graph
I'm upgrading some code which worked with QGIS 2.18 to now work with QGIS 3.4.5 and had the following snippet working to retrieve a set of points from a graph created by the QgsGraphBuilder function:
...
2
votes
0answers
27 views
Extract derived data fields from Shapefiles
I've uploaded shapefiles with professionally supplied survey data into QGIS and it all plots fine, then when I export the attributes table into Excel I see that the XYZ values are all zeros.
I know ...
-2
votes
0answers
23 views
Running QGIS Processing Modeler on web [closed]
I have recently made a QGIS model and now want to integrate it on my website. However, I have no clue whether such action is possible.
My model takes all the data from web sources so there is no need ...
2
votes
0answers
21 views
What is stored in Options|Advanced|PostgreSQL|connections|dbname|keys group in QGIS 3?
Since QGIS 3 in the Options|Advanced|PostgreSQL path referred to in the title there is a new group 'keys' as can be seen in this screenshot:
In old QGIS 2.X:
What kind of information is stored in ...
2
votes
0answers
13 views
QGIS 3.4.5 Attribute table expression in print composer not working
I just upgraded from QGIS 2.18 to the latest stable release (3.4.5).
I am trying to filter an attribute table added to a layout by using @atlas_pagename and I can see there is a match in the ...
1
vote
0answers
13 views
single sided buffer in pyqgis 3 gives “_core.QgsProcessingException: Error calculating single sided buffer” error
I am trying to create a single sided buffer around drains (polygon shapefile). The Distance parameter must be taken from a field in drains shp. Here is my code:
buf_out = self.dlg.lineEdit_3.text() ...
2
votes
1answer
61 views
Calculating the number of lines for each pair of origin/destination point - QGIS3
I have shapefile that looks like this: I need to make a matrix (or just to add a couple of fields in the attribute table, something like the origin-destination matrix), which will have the number of ...
0
votes
1answer
21 views
Label point layer with attribute of surrounding line features (QGIS 3.x)
I would like to label the points of my point layer with the name attributes of the surrounding line features. The result should be a list, with the names of all lines next to the point (f.e. 10 map ...
3
votes
1answer
47 views
Dynamically color labels in color of features (QGIS 3.x) [duplicate]
How do I dynamically color labels in the color of the labeled feature?
As you can see in the screenshot, the lines are in different colors, but the labels are just in black. As I know, I have to set ...
2
votes
2answers
53 views
Error Loading QGIS 3
Couldn't load plugin 'processing'
Every time I load QGIS 3.4 I get the below error
ImportError: dlopen(/Library/Frameworks/SQLite3.framework/Versions/E/Python/3.6/sqlite3/_sqlite3.cpython-36m-...
-1
votes
0answers
28 views
Intersecting WMS and shapefile using QGIS? [closed]
I am trying to make a roughness line file (.shp) and would therefore like to make an intersection between a buffer that I made and a orthophoto WMS file. Apparently it should be between two .shp files....
0
votes
0answers
21 views
Developing and desirably debugging pygis-3 processing scripts?
The writing of processing scripts in QGIS3 changed substantially. On the basis of many tutorials/blog posts and answers on this site I got a running processing script in QGIS3. But it was, for a lousy ...
1
vote
1answer
49 views
QGIS 3.6: Vector “Polygons to Lines” missing
I use the tool Vector-->Geometry Tools-->Polygons to Lines all the time. It is in the menu up until 3.4. In 3.6, that menu item is no longer available. Where did it go? Is there another way to do ...
1
vote
0answers
42 views
Getting QGIS processing script field calculator error?
I have a processing script that I created for QGIS 3.4.5 but I keep getting the following error:
Traceback (most recent call last): File "", line 66, in
processAlgorithm File
"C:/PROGRA~1/QGIS3~...
1
vote
0answers
34 views
Unexpected behaviour using Filter in QGIS 3.2
I have encountered an unexpected difference in how the Filter function works in QGIS 3.2 to previous versions (2.14 for example).
I used the Filter function to select a set of features based on a ...
1
vote
1answer
22 views
Error with categorized render tool in model builder QGIS 3.4.3
In my model, I'm trying to color my polygon layer using an xml file through categorized render tool (under cartography toolset). However, when I run the model the output file has the attribute data ...
2
votes
1answer
76 views
Label layer as symbol colors with QGIS 3
Is it possible to label a layer using same colors as the categorized symbology of that layer?
It is possible using the Rule-based labeling, but it can be difficult for a layer with many categories ...
