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Questions tagged [qgis-3]

for questions specific to the 3.x series of QGIS.

783 questions with no upvoted or accepted answers
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52 views

QGIS: check and repair geometry

I'm studying how to check and repair geometry correctly and found the "check geometry" tool which seems to work fine. However there are also tools called "check validity" and "fix geometry" which ...
2
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0answers
79 views

Error opening qgis_dev 3.9.0-55

I've installed qgis_dev 3.9.0-55 through the OSGEOW64 installer on my win7 machine. I've got the error message proj_6_2.dll is missing (qgis_dev with grass) or "could not load qgis_app.dll" (qgis-dev ...
2
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0answers
62 views

Split selected feature with selected line from another layer in QGIS LTR 3.4.9

Can't seem to find that tool since I switched from QGIS 2.14 to 3.4.9 It doesn't seem to be included in the Advance Digitizing Toolbar like before.For now, I re-installed 2.14 since I need to use this ...
2
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0answers
135 views

QgsVectorLayer.IsValid() always returns False?

I'm writing a standalone Python script which involves some geoprocessing using qgis libs. Unfortunetely, I couldn't manage to properly instantiate a vector layer - every time i run .isValid() on ...
2
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0answers
43 views

Stop QGIS opening multiple taskbar items?

I have QGIS pinned to my taskbar, right clicking shows that it's named "QGIS Desktop 3.8.2". When I run it and open projects some of them open a new taskbar item called "QGIS 3". This also happens ...
2
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1answer
136 views

MapProxy : possible config issue?

I created a yaml config file and ran it with mapproxy-util serve-develop my-config.yaml The file contains this: services: demo: tms: kml: wmts: capabilities: http://localhost:8080/wmts/1....
2
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0answers
26 views

Clipping interpolation layer to a coastal boundary in QGIS 3.6?

I have created an interpolation layer and want to clip it so I don't see the area outside the coastal boundary. map showing area to be clipped:
2
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0answers
28 views

QGIS3 application not there after installing

I installed QGIS3 on my computer at work. The installation was completed without errors. But there is no QGIS application on the computer. The folder exists though, and it also contains all the other ...
2
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0answers
218 views

Generating MBTiles in QGIS3.4?

Similar to this question: Generating map tiles with QGIS 3.6?, how is it possible to create MBTiles from a raster ? (I operate QGIS 3.4 LRT) I have tried Save As.... and selecting format: MBTILES, ...
2
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0answers
34 views

Using multiple fields for random points in polygons QGIS?

I'm quite new to QGIS and I have a question about the 'random points in polygons' functionality. Is it possible to use more than one field from the attibute table when using 'random points in ...
2
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1answer
47 views

QGIS 3 : How to use crtl + space properly?

When I select a layer and do Ctrl+space, all layers become temporarily hidden, including the active one. The other ones are still checked but the check box is greyed. But what is this shortcut meant ...
2
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0answers
84 views

QGIS 3 system date format is not assumed

The system date format is 'dd/MM/yyyy', and QGIS recognizes this on the Options / General tab, however it does not assume this format anywhere else in itself. Any loaded feature that has a date or ...
2
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0answers
86 views

Slow counting of points in polygon in QGIS 3.4

I am working on a plugin to count the point in polygons by PyQGIS in QGIS 3.4, and I found that compared to the same function in QGIS 2.18, it is very slow. I do not know the reason. My code is listed ...
2
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0answers
35 views

Extract Raster by Layer - empty raster

I am quite new to QGIS but used some ArcGIS before, so I thought this should be very easy to do, but I dont get good results. I did the following steps both in 3.8 and 3.4: Import Raster-Layer and ...
2
votes
1answer
100 views

Setting value to defaults Layer properties using PyQGIS 3

I have a vector layer, how to set defaults value in fields from the Python console. Layer Properties / Attributes Form / Defaults | In option: Default value |______________|
2
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0answers
46 views

Possible bottleneck in QGIS 1:n relation?

I've set up a 1:n relation linking two layers of the same geopackage. That are about 200k polygons in parcels and 700k rows in owners (non spatial). Now it works as expected but it is painstakingly ...
2
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0answers
154 views

Requesting Styled Google Maps XYZ tiles with QGIS seems to ignore colors

At the time of posting this question unauthenticated requests for Google Maps tiles work. E.g. the following URL scheme would correctly load the tile shown below https://mt1.google.com/vt/lyrs=r&...
2
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0answers
138 views

QGIS3 run model with python script

I want to run a model with a python script, including the parameters, because I can't "translate" the model easily into a script. I have tried to run a copy of the processing log after running the ...
2
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0answers
53 views

Delayed function calling inside QgsTask

I try to add a function to the qt event loop via QTimer.singleShot(...) from within a QgsTask. However the function is never executed. I wrote a short script that isolates this issue: import time ...
2
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0answers
73 views

Accessing downloaded shapefiles/attribute data?

Using 3.8, I am attempting to create a simple map of the UK showing the county boundaries, with a couple of specific locations shown for reference. My approach for attempting this has been to attempt ...
2
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0answers
25 views

QGIS 3.4 Modeler gives error on non-required parameter?

I created a model which is asking to input 20 OPTIONAL parameters for vector layers. But when the user does not enter a value for any of the 20 parameters, QGIS returns an error. Traceback (most ...
2
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0answers
34 views

Adding action to map in QGIS when link to actions menu item is missing?

I am running qgis 3.8.0 zanzibar on ubuntu 18.04. I am trying to set a hyper link on a point on the sample map (Alaska). A casual perusal tells me that I should set up an action. https://www....
2
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1answer
78 views

Create tabs for the QGIS plugin interface using Qt Creator

Is it possible to create tabs for QGIS plugin using Qt Creator? (Something like the image I attached) I am trying to group the functionalities I developed for QGIS plugin and I think using multiple ...
2
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0answers
25 views

Symbolising 2.5D polyline based on slope of each segment using QGIS?

I have a 2.5D polyline (each vertex has an elevation value) of a hiking route. I would like to change the line width depending on the slope of each segment in order to visualise how difficult each ...
2
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0answers
68 views

Converting lat/long to EPSG:27700 in geometry generator expression

I have incorporated a geometry generator into a style in QGIS 3.4 which creates a callout line from a feature to its relevant spatial position. For reasons out of my control our projects use CRS: ...
2
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0answers
55 views

Building polygons and the lines that represent their edges in QGIS3

I want to create polygons from intersecting lines using QGIS 3, each polygon having a unique ID attribute. In addition to the polygonal areas, I need the lines that represent their edges; each of ...
2
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0answers
32 views

Rasterize a geometry using gdal.RasterizeLayer()

I am writing a processing script using QGIS 3.4. I need to rasterize a polygon using gdal.RasterizeLayer. The problem is the polygon is a list of QgsGeometry objects and not a layer. n = (2*radiusInt)...
2
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0answers
61 views

Getting results from processing.run GRASS r.resample in PyQGIS

I am trying to get output from r.resample in a stand-alone PYQGIS application. The code runs and does not show any errors, but it does not save an output file (i.e. 'c:/path/to/output.tif'). As far as ...
2
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0answers
88 views

QGIS 3.4.8 Filter Expression for OSM values

I'm trying to complete the seemingly basic task of a filter select for a layer of OSM data pulled from https://download.openstreetmap.fr/extracts/africa/. It's an .osm.pbf which I added to my project ...
2
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0answers
58 views

How to use the Raster Calculator in PyQGIS (Console) in QGIS 3?

I want to use a script to do some raster calculations. I found this and this posts which seem to answer this question, however, it seems that they work for QGIS 2 and not for QGIS 3. I think the ...
2
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0answers
37 views

Functionalities of expression builder in Autofield plugin available in QGIS 3.4?

Basically, what I try to do is automated calculation while editing (not with field calculator). In QGIS 2.18 you could do automated calculations while editing with the Autofield Plugin. Since QGIS 3....
2
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0answers
45 views

How to use a plugin in the QGIS 3.4 toolbox

I have version 3.4 of QGIS and I want to generate a model, so I need SCP tools (unsupervised classification). I can not find a way to add it to the tool box in order to finish my working model.
2
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0answers
50 views

Automatically change symbol modified in style manager using QGIS3

I used Style Manager to add some symbols. Then I assigned them to a feature/layer. But if I change the Symbol / style (only via style editor), the layer will not change automatically. How can I ...
2
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0answers
26 views

Copying vertex coordinates from one line into another with same geometry type

I have the following QGIS version. How is possible to copy the vertex data information from a line into another line? Maybe a certain plugin shall be used for this purpose. The data are 407 points ...
2
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0answers
50 views

Finding Intersection Points in Stream Network using QGIS?

I have a stream network and I want to find the red points as shown below. I have tried using Q-chainage and Line Intersection feature in QGIS but it gives more than expected number of points. The red ...
2
votes
1answer
72 views

No options for “Print layout” while animating lines with mmqgis

I am trying to use the mmqgis animate lines tool to animate some lines. But for some reason the dialogue box has the "print layout" section greyed out. The line layer is called 'POC 3 to POC 4 shape',...
2
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0answers
28 views

Merge Vectorfile Outputs from Model Batchprocess in QGIS

I have written a model in QGIS 3.6 that allows to vectorize the outlines of raster layers containing measurement data. I run this model as a batch process to vectorize several field outlines in one go....
2
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0answers
31 views

QGIS configuration: Import Style Libary

I would like to script QGIS to import a style library as part as a configuration for a new user. By Python commands, how do I instruct QGIS to do what a QGIS user can do with the "Import Items" ...
2
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0answers
70 views

QGIS - creating cross section to meet contour line

How can I automate the process of creating a shapefile containing cross-sections of a river centreline that will meet to a set distance given by a contour shapefile? Is there a plugin or a set of ...
2
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0answers
53 views

Calculating share of overlapping areas via aggregate function in a virtual field

I'm trying to calculate the shared area for several overlapping areas. I need a dynamic solution in order to get automatically calculated statistics when drawing new polygons. The target area is in ...
2
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0answers
201 views

Python warnings in QGIS 3.4

I just opened the QGIS and this appeared. What does it mean? Is it serious problems? warning:/Applications/QGIS3.6.app/Contents/MacOS/../Resources/python/qgis/utils.py:672: DeprecationWarning: the ...
2
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0answers
182 views

QGIS crashes when running script from Processing Script Editor

Encountering this weird bug. I'm using QGIS 3.4.7. I am trying to write a script but it crashes when I run it from the editor. But it does not crash when run from the Processing Toolbox. Right now the ...
2
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0answers
33 views

Algorithm “qgis:difference” returns multiple heterogeneous outputs

I use the qgis:difference algorithm but it returns multi-type outputs. Sometimes it's a QgsVectorLayer but sometimes a str such as : output_.... My question is : when the algorithm returns an empty ...
2
votes
1answer
75 views

processing.run() returns string instead of QgsVectorLayer with QgsProcessingFeatureSourceDefinition as parameter

I try to run qgis:difference on selected features of 2 layers. But the result of my code : parameters = {'INPUT': QgsProcessingFeatureSourceDefinition(layer1.id(), True), 'OVERLAY': ...
2
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0answers
76 views

Migrate QGIS2 projects to QGIS3

I have about 40 QGIS2 projects. If I open them with QGIS3 labels and svg icons are not displayed. I don't know if there is any other feature that is not working when upgrading to QGIS3, but I suppose ...
2
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0answers
42 views

Confusing result of raster calculator in QGIS

I'm confused about the results that I get from the raster calculator in QGIS. I'm trying to delete the cells of a raster who are prone to flooding. However, a part of my raster is wrongly classified ...
2
votes
0answers
239 views

QGIS 3 Value Relation current_value() not working in custom ui form

I have a custom UI form made with Qt Designer with a couple of dropdown list, so I can easily edit a layer. I use a Value Relation on those fields to filter the displayed data. The problem is the ...
2
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0answers
33 views

Still a Python27 folder?

Can anybody tell me why there is still a python27 folder along with the python37 folder in the latest (3.x) QGIS releases?
2
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0answers
29 views

Calling a Python function for each page in an atlas

I have made a script to do some calculations for each page of a QGIS atlas (QGIS Atlas with insert map) The script is adjusting the bounding box of a map on the layout page. To make it run for each ...
2
votes
0answers
86 views

Disconnect between raster symbology in Layers Panel and Layer Properties (QGIS 3)

I'm working on a Python plugin for QGIS that applies a customised colorRampItemList to a single band raster. The result displays correctly on the map and in the Layers Panel but incorrectly in the ...