Questions tagged [qgis-3]

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

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1answer
210 views

QGIS Server 3.10 LTR on Ubuntu 18.04 LTS not working

I have a virtual server which is running Ubuntu 18.04. I've installed the qgis repo for ubuntu-ltr and followed along the tutorial: https://docs.qgis.org/3.10/en/docs/training_manual/qgis_server/...
3
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1answer
129 views

Invalid geometry in point layer when running 'Count points in polygon'

I have a persistent problem I can't seem to fix. I'm trying to run Count points in polygon. I keep getting this error: Feature (747) has invalid geometry. Please fix the geometry or change the ...
4
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0answers
31 views

How to use all QGIS 3 custom widgets in Qt Designer?

For example, QGIS 3.4 has various custom widgets such as QgsFieldValuesLineEdit and QgsColorWheel (and later versions have even more widgets) but they are not listed in the QGIS custom widgets list of ...
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1answer
49 views

A simple way to merge lines separated by a space in QGIS

In QGIS after creating contour lines by extracting them from a DEM (Extraction > Contour) and smoothing them (Line Smoothing) I noticed this situation: In order to smooth out the corners ...
0
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2answers
100 views

QGIS 3.10 not recognising projection information from raster created using GDAL

Problem QGIS 3.10 only partly reads projection information from raster file however QGIS 3.4 correctly reads information from same raster file. I thought I had an issue creating the raster – I may ...
1
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0answers
27 views

Cannot load WFS with BBOX Parameters via Python script

I tried to load a WFS with BBox-Parameters using a python script. The script is working, but loads the whole layer, instead of just the part inside the set BBox. The URL itself works on both the ...
2
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1answer
71 views

QGIS 3.4 set transparency only for some layers below

I‘m working on a geomorphological map of a river and its sourroundings. As a base I have a topographic map and a DEM for the pre-mapping. The topographic map is not accurate enough in the river gulley,...
2
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1answer
45 views

Linking points with lines for display in QGIS

I have 2 point shapefiles which contain lat and longs and I need to connect these with a line for display, not analysis. I am using QGIS 3.4. To explain further, for one individual species/animal (i.e....
2
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1answer
181 views

Joining many points with lines?

I'm working with QGIS 3.4.3 and have a list of addresses (1500ish) that I need to map into lines. I have a CSV file having a start and end of each street and also have the same list separated in two ...
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0answers
21 views

After start editing, the editing toolbar remains inactive in QGIS

With respect to my previous question Disconnect editingStarted in PyQGIS , While doing some research for question, I found some details to stop editingStarted signal with following code. layer=iface....
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2answers
343 views

QGIS 3 building density calculations

I have layer of buildings (polygons), and in attribute table contains number of buildings, floor area of buildings etc. I would like to know how many buildings (#) is per Ha or km2, and building area ...
1
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1answer
18 views

How can I set the default layout export resolution in pyQgis?

I want to change the default export resolution (default value = 300 dpi) programatically when I open the layout designer l = QgsPrintLayout(project) l.initializeDefaults() l.setUnits(QgsUnitTypes....
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1answer
28 views

Attempting to Draw Electricity Grid - Need Maximum Segment Length and Precise GPS Coordinates

I am attempting to draw an electricity grid (poles and cables) using QGIS. I need to ensure that each pole is a maximum of 50m apart, and then I need to measure the total length of the grid and ...
0
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1answer
55 views

Disconnect editingStarted in PyQGIS

I am creating a Plugin, where on addFeature button, first user will get a dialog box to select the type of feature user wants to draw. On the basis of users choice, other editing constraints will get ...
3
votes
3answers
277 views

Variable width buffer in QGIS

Is there any built-in tool in QGIS that I can use to buffer points to a variable size (I want to circles around the points, with widths dependent on an attribute in the point layer)? The Vector/...
1
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1answer
40 views

Fill in areas between lines with polygons?

I have to make a geographical map. I have to fill in the gaps between the lines with polygons. Is there a possibility to just trace those lines automatically? I have to do everything manually now, ...
0
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1answer
215 views

Merge connected lines and split them after set unequal distances

I need to edit line features in QGIS 3.4.4. I have more than 1000 line features that I want to first merge and then split. The line features describe roads in useless intervals, my goal is to ...
0
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1answer
36 views

QGIS 3.10.5 Installation aborted

I'm trying to download QGIS 3.10.5 64-bit to my Windows 10 Laptop, but for some reason, the installation decided to cancel. It stopped nearly 4/5 of the way when running the 'Extract:qgis_zh-Hans.qm'....
3
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1answer
42 views

QGIS 3 relationship strength “Composition”

is there somebody who can explain the usage of the relationship strength "Composition" in QGIS 3? What can the user do in detail when setting to "Composition"? Relationship ...
2
votes
1answer
542 views

Install QGIS 3.4 with GRASS support in Ubuntu 18.04

I can install QGIS3.X but cannot run a GRASS process. I get the popup: This algorithm cannot be run :-( GRASS 7 can't be found on this system from a shell. Please install it or configure your ...
0
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1answer
59 views

Displaying map title in PyQGIS

I have the following map but I don't know how to make a title appear on top of it. Any suggestion on how to?
0
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1answer
29 views

Printing Output in PyQGIS Plugin

In developing a PyQGIS plugin, I would like to be able to print out variable values to ensure that my program has the desired functionality. I am aware that I can print messages with something like ...
0
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2answers
123 views

Do SAGA tools work on QGIS 3.10.7?

Is anyone successfully using SAGA tools in QGIS 3.10.7? I have downloaded QGIS 3.10.7 on multiple PCs and a Mac. All of them have resulted in the same problem when I try to run SAGA tools. A message ...
3
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0answers
30 views

Using the conditional branch algorithm in QGIS modeler gives unexpected results

I'm trying to implement the new conditional branch algorithm in a model with the following statements: if( @Udtræk_til_grøfter_OUTPUT > 0, true, false) if( @Udtræk_til_grøfter_OUTPUT <= 0, ...
3
votes
1answer
47 views

Change datasource of multiple layers from one db to other db in QGIS project?

I have a QGIS project with around 100 layers referring to a postgres database. Since we're migrating to a new server, the database will be transfered too, but will be given a new IP. The connection ...
2
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0answers
143 views

Query a QGIS server WMTS using a RESTful URL as defined by the OGC

Context I'd like to use the WMTS from a QGIS server to serve a raster image as a base map in OpenStreetMap. Description of the issue I have set up a QGIS server to serve my raster image. Both WMS and ...
0
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1answer
66 views

QGIS function like ArcGIS Planarize

I have a city road network. I have to divide sections that are separated by intersections into one level. With ArcGIS this is done with Planarize. I tried split commands, but it applies to all ...
4
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2answers
186 views

Display lines which share segments by offsetting them only where they overlap?

Background: As part of a route selection process I have multiple route options which often share segments. I need to keep the underlying data correct while displaying all routes in a way that they ...
1
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1answer
164 views

Setting selection border color in red and save the map of the resulting selection

I'm attempting to create a plugin in QGIS 3 in order to zoom on a selected feature and get the map picture exported in .jpg format. I've been able to perform the zoom and selection of my selection, ...
0
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1answer
29 views

Where is the source code of QGIS Processing algorithms?

I am beginning to learn QGIS 3 up from QGIS 2. I see many changes. In QGIS 2 one could find the scripts for the algorithms located in the Processing Toolbox. But here in QGIS 3 I cannot find the ...
2
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1answer
33 views

How to easily toggle outlines and fills for polygon layers (in QGIS 3.x)?

So I want to be able to easily toggle outlines and fills for polygon layers in the Layers List. I managed to make two rules (both with the rule 'true') and then they will show up in the Layers List: ...
2
votes
1answer
76 views

Adding feature to PostGIS layer that has joins is really slow

I have a large project that I've been setting up to work with QGIS 3.12 and I have now hit a problem with using "joins" to join several attribute tables with a geometric one. I have reduced the ...
3
votes
2answers
77 views

Adjusting format labelling view through map scale

I am using 3.10 QGIS. I want to set the label view adjusting with map scale when zoom in zoom out. Here is an example. I want to make the zoom out, on the 2nd picture, label adjusting to the map ...
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0answers
37 views

How do I get the number of rows in an attribute table? [closed]

In processing modeler in Qgis 3.14, how do I get the number of rows in an attribute table?
3
votes
3answers
259 views

QGIS3 Shape Digitizing Circles is Drawing Improperly

I'm trying to draw a circle in QGIS 3 with the shape digitizing toolbar. I've tried several of the "add circle" options and they all look normal while drawing, but once I click to finish the shape it ...
2
votes
1answer
155 views

Merging DEMs in QGIS?

Not the first problem I've had with DEMs in QGIS 3.4. Trying to merge 6 DEM tiles together into one. Process for this is simple: go to Raster --> Miscellaneous --> Merge. Once in the menu, select ...
0
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1answer
150 views

.tif to PCraster format conversion in QGIS 3.2

I am using QGIS 3.2 and trying to convert a resampled .tif file into PCRaster format which is used for a downstream model. Unfortunately when i try to export the resampled.tif file into PCRaster ...
1
vote
1answer
37 views

QGIS 3: How to count the mean of shapefile attributes that lie in a specific area

so I have a shapefile with buildings and the shapefile has the height of the buildings in the attribute table. I have a second shapefile with the districts the buildings are located in. Now I would ...
0
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0answers
18 views

Supervised Classification Sentinel 2 using QGIS Semi Automatic Classification Plugins: virtual raster/virtual band set

I am using QGIS semi-automatic classification plugin, supervised classification (LC Classification) of Sentinel 2. My Question is: According to the online tutorials (please check the tutorial: https://...
0
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1answer
36 views

set z-value from table

In qgis 3, postgis, no DEM and zero python knowledge. I've got linestring 3d but Z coordinates is empty, Z-values are stored in table. Z1 for the first node, Z2 for the last node. I found a lot of ...
1
vote
1answer
48 views

Progress bar does not show progress during processing

I am trying to show the progress in the progress bar, but it is not running, I have seen several solutions but none has solved me. This is part of the code that I am using : def progress_changed(...
1
vote
1answer
114 views

How to resize label in PyQGIS?

How can i make it so the legend on the left bottom don't cover the map?
3
votes
1answer
43 views

Varying page size of maps within an Atlas in QGIS?

I would like to create an atlas of a series of maps covering a number of woodlands and to have them all at the same map scale. This would work best visually if some of the maps were in landscape, and ...
2
votes
1answer
37 views

Intersect overlapping entities and their attributes

I have a shapefile containing 6 classes of polygons on QGis 3.14. Some of these polygons overlap each others, but they're not geometry errors or duplicates, just polygons with different attributes. ...
0
votes
1answer
93 views

Loading layers from PostGIS db (populated with osm2pgsql) in QGIS?

I have downloaded some OSM data from geofabrik and used this to create a PostgreSQL/PostGIS database using the osm2pgsql tool: osm2pgsql -G -d <db> -U postgres myfile.osm Examining the ...
0
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0answers
22 views

How can you send by Python console an expression to a layer property and activate its corresponding check box

Try this code but it has only worked for me with fixed and short values for example 'hello' or '777' layer = iface.activeLayer() idx = layer.fields().indexFromName('cp') layer....
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0answers
23 views

How to use a IF statement to change colors for layers using PyQgis?

How to change the colors according the values in 'C_index' field? I tried a FOR loop, in order to read all values in this field, and an IF STATEMENT to set all 'red' and 'blue' values to the same ...
0
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0answers
22 views

Create QGIS 3.14 PostGIS local connection without user name or password?

I used to be able to create local PostGIS connections in QGIS (as of 3.12.x) without supplying the user name or password. On the local test machine, PostgreSQL is set up to trust authentication, so it ...
-1
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1answer
53 views

QGIS 3x problem with CRS for comma delimited layer

Good afternoon, I would like to overlay my .csv comma delimited layers in QGIS 3x properly. I have got the Ordnance Survey Maps as the raster players, which CRS is EPSG 27700 1936 British National ...
2
votes
1answer
168 views

Feature Count for Categorized Layers with the Atlas function of Print Layout in QGIS 3

In QGIS, is it possible to count the features of each class in a categorized layer where the features being counted are limited to those that are inside the current atlas feature? I have tried ...

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