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Questions tagged [qgis-3]

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

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4 views

Call the QGIS 3D view using pyqgis

I am working on creating a change detection script for QGIS3, that detects the differences between two DEMs and highlights the changes. Everything is working well but I have been unable to get the 3D ...
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0answers
3 views

Handling .osm data in QGIS 3.4 Processing Modeler

I'm trying to add some data in OSM file format in a QGIS 3.4 Graphical Modeler. I'm interested in the line type of data (layer ID 1) inside .osm file but I can only access point data (layer ID 0). The ...
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0answers
15 views

QGIS 3.4 Problem with short PATH

I've installed QGIS 3.4 but seems that installation scripts not work so well! I launch grass GIS 7.4.2 from qgis 2.18 works but from QGIS 3.4 no! the difference is in a statment of bin/grass74.bat ...
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0answers
11 views

Counting points in a scratch layer poygon

I'm using QGIS 3 I am trying to count the points in a scratch layer polygon. when I use the count points in a polygon tool it says there are no points in my polygon which is untrue. I figured the ...
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0answers
14 views

PyQGIS - Grass 7 r.reclass

I want to run the r.reclass tool in python on a raster layer to reclassify 1 value (and leave the rest the way they are). I want to reclassify the pixel value '255' to '-1' Here is my best attempt ...
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1answer
35 views

Create a drop-down menu in a QGIS Processing script?

I'm trying to write a QGIS processing script using the new API (3.4), but I hardly find any documentation. Based on this excellent resource by Anita Graser (https://anitagraser.com/2018/03/25/...
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0answers
22 views

Vector Rasterize Error

I am running QGIS 3.4.4 With GRASS 7.4.4 and I get an error while rasterizing a vector layer and I don't know why. The same error pops up while using GDAL->Rasterize(vector to raster) and while using ...
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0answers
24 views

Map view does not render full SVG, but layers pane and print layout does?

In map view where I want to do all design and small changes the SVGs for "MELLANTID" does not render the added outline, only original size. The SVG for "SJUKVARD" only renders the left half of the SVG,...
3
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1answer
109 views

Use intersection in field calculator

I want to use the tool intersects in the field calculator. If the condition is true, I want to set a result field to a specific number. The field calculator doesn't accept my expression but I can not ...
4
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1answer
114 views

Distortion of City -Boundary-Polygons proportional to population size in QGIS?

Is there a way to distort the size of polygons proportional to their population size (as in column in the attribute table)? I want to create a map that looks similar to this: the cartogram2 plugin ...
2
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1answer
33 views

Make color transparent

I've downloaded some maps from copernicus, e.g. this map: http://marine.copernicus.eu/services-portfolio/access-to-products/?option=com_csw&view=details&product_id=...
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40 views

Layers do not align after projection using QGIS?

I work on QGIS 3.4.4. My data I have 4 .tif rasters that will eventually have to be stitched together. The rasters' metadata suggest EPSG:3577 as the initial CRS. I also have a constriction point ...
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1answer
40 views

How to read the error when writing vector files in QGIS 3.0

Upgraded to QGIS 3.0 and now I cant read writer errors. The following (post 2to3) code doesnt print the error to the console: CRS=QgsCoordinateReferenceSystem().fromEpsgId(4326) error = ...
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0answers
46 views

Map not showing while following tutorial for QGIS [on hold]

1I downloaded and installed QGIS 3.4 and tried to load an example shapefile layer as described in this tutorial using the provided shapefiles. But the images are not showing up. I tried to uninstall/...
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0answers
7 views

How to enable tracing in QGIS 3 beyond applications for adding polygon purposes?

I have used the enable tracing feature in QGIS 3 to create new polygons (Add polygon feature), and it works very well. However, i have not been able to use it for other purposes beyond that, for ...
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0answers
16 views

Configuring QGIS new OAuth2 support for WMS or WFS

Has anyone successfully configured QGIS new OAuth2 support for a WMS or WFS service? I have an ArcGIS 10.6.1 service published as a WFS service but cannot get past the OAuth2 authentication.
3
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1answer
55 views

Modeling iterative processes in QGIS 3

In the QGIS version 2.X, there was an Iterative Button from the algorithm also available for the algorithm used inside the processing modeller. Actually, I use version 3.2 and 3.4 and can not find it....
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1answer
37 views

Get progression bar into PyQGIS 3 standalone script

When I run a treatment inside QGIS with Processing toolbox (native algorithms) I get a progression bar : Is there a way to use this percentage inside a standalone PyQGIS script? I searched in the ...
2
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1answer
85 views

QGIS 3.4.4 sorts numerical values as text, solution?

I'm trying to sort my numerical values in my attribute table but instead of getting 1, 2, 3 I get 1, 10, 100, 100 etc. When searching for a solution here on Stack Exchange, many people with earlier ...
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1answer
36 views

Problems opening MapSurfer layers

Why won't Mapsurfer OSM layers open anymore from the QuickMapServices plugin in QGIS version 3
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0answers
20 views

Unable to use PyQGIS since python is unable to import qgis libraries

I am using Ubuntu 18.04. I have installed QGIS 3.4.4 Madeira on my laptop. I am learning PyQGIS. I have found these lines of code that I have executed in my terminal but I get a traceback saying that ...
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1answer
25 views

Identifying selected feature using PyQGIS?

If I select a feature and run self.iface.actionIdentify().trigger() it will open the identify window but won't open the selected feature's data, how can I make it open the data of the selected feature?...
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0answers
17 views

Getting rid of qt.qpa.plugin Error?

I am trying to execute standalone python script outside QGIS. But when I try to initialize Qgs Application , it give me below error . I don't have any idea how to get rid of it . from qgis.core ...
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1answer
30 views

QGIS 3: How to rename attribute/field names for Geopackage Layer

Issue: I need to rename several attributes/fields in a geopackage layer. How to do this? Linked Issue: there are numerous pages on how to rename the attributes/fields of a shapefile. However there do ...
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0answers
43 views
+50

Using GRASS in Python script QGIS 3

I am creating a Python script in QGIS 3 and I want to use the processing module. I want to transform my raster file to a vector file with the GRASS algorithm r.to.vect. My problem here is that the ...
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2answers
42 views

How to rename duplicated layers in QGIS3? [on hold]

I duplicated a layer ("Buildings") in QGIS 3.4.4 and with the Query Builder under Source I selected to just display schools. Subsequently I renamed this layer "Schools" by rightclicking on the layer, ...
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0answers
15 views

QGIS 3.4 and loading raster from multiple variable NetCDF file

Using QGIS version 3.4.4 when loading a NetCDF file out.nc which contains multiple variables on a fresh Ubuntu 18.04 install I encounter the following error: CRITICAL Invalid Layer : Raster layer ...
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0answers
27 views

Unable to load output layer from Python algorithm in QGIS 3

I'm building a Python algorithm for QGIS 3, to be run from the Processing Toolbox. I've finished debugging the algorithm body, which seems to work, but QGIS is unable to load its output. To summarize,...
1
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1answer
41 views

PyQGIS - Plugin returns error from processAlgorithm. Invalid Result

I've written a script which automatically creates a print layout and exports it. Now I'm trying to integrate the code into my plugin's code. The plugin has some existing functionality and I'm adding ...
1
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1answer
31 views

Create geometry column in Geopackage with SQL

How to create a table with geometry column that is recognized as spatial layer? I use the DB manager from QGIS 3.4.2 I use the following: CREATE TABLE 'sample_attribute_with_geometry' ( id INTEGER ...
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0answers
33 views

No icons when installing QGIS 3.4.4

I've been trying to install QGIS 3.4.4 Madeira on Windows 10 x64. I've tried the network installer and the standalone version, both of which say they installed successfully but no desktop or start ...
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1answer
32 views

Move QGIS3 bookmark panel to be in the menu bar without creating a plugin

Is it possible to move the Bookmarks from a panel to be in the top menu bar - so you would get ...Edit--View--Bookmarks--Layer... and clicking on Bookmarks have a dropdown that has Sydney, Melbourne ...
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0answers
19 views

QgsFeatureRequest() with a string search within QGIS3 Processing Script [on hold]

I'm trying to select features using a string comparison within my script using a QgsFeatureRequest() and getFeatures() roadsRequest = QgsFeatureRequest() roadsExpression = str(roadsIDField[0]) + ' ...
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0answers
16 views

Filtering the atribute table on the atlas page so it only shows atributes of objects related to the featured object

I have been trying to make an atlas of cadasters, using different themes and rule-based symbolology, but one thing doesn't seem to work. On each atlas-page I want to put a table showing the ...
1
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2answers
41 views

Opening multiple attribute tables using .showAttributeTables()

I've got a question about .showAttributeTables() - i'm trying to open two attrbute tables at the end of a query (selection of lines within a polygon layer) - I thought I could simply do somthing like ...
1
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0answers
32 views

QGIS 3.4.4 Crash on vertex editor [closed]

I've just installed QGIS 3.4.4. Each time I edit any layer, as soon as I select the vertex editor (single shapefile) I receive the 'unknown exception error'. The error then occurs with ANY edit in any ...
4
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2answers
231 views

Is there a maximum number of features that QGIS can save into a shapefile?

I have a very large .gdb that I want to reduce to my study area. Unfortunately, the study area is still quite big. I could select features that intersected my study area but when I tried Export > ...
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0answers
16 views

Problem with repo qgis.org/debian “does not have a Release file”

When I include deb https://qgis.org/debian/ buster main deb-src https:://qgis.org/debian/ buster main in my /etc/apt/sources.list file, and run sudo apt uptdate I get: E: The repository 'https://...
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2answers
99 views

Black theme (“Night Mapping”) doesn't load

At work we are using QGIS 3. When we were using QGIS 2 I enjoyed working with the black theme, called Night Mapping, for healthy eyes, etc. With QGIS 3, when I click on the menu of the themes and pick ...
2
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0answers
36 views

QGIS 3.44 heatmap to contour file

I am trying to convert a point file, currently displayed into a contour file. The methods that I have tried, all expect a raster file as an input, but my source file is a vector file points, i.e. I ...
2
votes
1answer
42 views

Customizing QGIS interface?

I'm trying to customize QGIS 3.4 interface to allow data display only. None of the default QGIS geospatial data editing functionalities should be exposed to the end user. Also, the users should not be ...
3
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0answers
39 views

How to test the geometry type from a list of layers and then join it with PyQGIS 3

Summarizing my problem, I'm a beginner and I'm developing a plugin that will be able to do several spatial joins. For this, it will have to separate the spatial from the non-spatial layers and do the ...
3
votes
1answer
33 views

Why are labels and looks different between print layout and map canvas at same scale?

I know that some of my items uses map unit as size unit, others mm and labels points. But the map canvas where I do all my changes should still look exactly the same in print layout if I'm using the ...
1
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3answers
71 views

How to fill unconnected areas in polygon with the same attribute

I am trying to fill in the gaps with the same attribute. These arrowed areas belong to a city called 'Westbank', but the thing is, these areas are unconnected, how can I make a polygon out of areas ...
3
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3answers
77 views

QGIS 3.4 : Add points to exact locations?

I would like to add several coordinates at specific British National Grid Easting and Northing values. I know this can be done by bringing in a .csv, but I want to know is there a way to manually ...
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0answers
52 views

Difference between DEM raster in QGIS 2.18 and 3.4.4 [duplicate]

I came across a really strange problem. Untill today i always worked in QGIS 2.18. Now i wanted to upgraded to 3.4.4 ( it was already downloaded but hadn't used it yet) When opening my QGIS ...
1
vote
1answer
76 views

Filter layerlist in snapping dock of QGIS3 to show only layers selected in the layer-dock (TOC)

I would like to filter the layerlist in the "Snapping and Digitizing Options"-Dock so that only layers are shown which are selected in the TOC of the QGIS-Layer-Dock. At the moment I use a workaround ...
1
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1answer
50 views

Stuck on how to list loaded layers in QGIS 3 via Python

I've stuck on a issue about getting a list of loaded layers. I've two layers loaded, one spatial (point, line or area) and another one non spatial (postgresql table). I've tried this code but it lists ...
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3answers
48 views

Reclassifying by layer in QGIS?

I am trying to reclassify a DEM by using the new Reclassify by layer tool in QGIS3. I am using the following input table: However, as shown in below screenshot of the tool, the Minimum class value ...
1
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1answer
27 views

How to get file path from vector layer object in QGIS 3.x processing framework?

Using the QGIS 3.x processing framework, given a vector layer as an input parameter: (from the default script template) def initAlgorithm(self, config=None): self.addParameter( ...