Questions tagged [qgis-3]

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

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1answer
108 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',...
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1answer
41 views

Why do I get coordinates in QGIS3 as nnnnnn; nnnnnn instead of Lat/Lon when I upload a shapefile supposedly projected in WGS84 [duplicate]

I received a couple of shapefiles made in France supposed to be projected in WGS84. When I upload them to QGIS3, it recognizes them as WGS84. However, their coordinates are displayed in a strange ...
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17 views

Having wrong CRS from graphical modeler output

I'm using graphical modeler to reclasify some rasters and then make another calculus, but when I try my model only with the first step (reclassify) I get an output with different crs of the input. I'm ...
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1answer
29 views

Writing the table layer_styles in a Geopackage

I made a pyQGIS script to backup the PostGIS tables of my team. I needed to save each table style in the Gpkg's layer_styles. Here's an extract of how I've done but I would prefer to implement the ...
0
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1answer
50 views

Save processing modeler output layers to project folder/relative path?

I am building an algorithm in the processing modeler which takes a csv file as input and creates a number of vector layers as output. I would like to automatically save these layers in the same folder ...
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0answers
28 views

QGIS software missing on laptop after trying to update to latest version

I am facing an issue with QGIS installation. I tried to upgrade my QGIS to version QGIS 3.14, I couldn't locate it on my laptop anymore. However, I can see it in the uninstall section of my laptop. I ...
2
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1answer
115 views

Moving point A to point B with attributes using QGIS

I have an A layer containing points with a XX attribute. I would like to move (on points A) the points of a layer B with the same XX attribute as A. There is no notion of distances (from a few cm to ...
2
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1answer
51 views

Select by Expression and Extract by Expression generate different results

I have a polygon layer and want to extract all Polygons with the field "street" = 1. When I use "Select by Expression" I get the following correct result: However, when I use &...
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0answers
11 views

User defined folder location for QGIS3 temp files in Pycharm

I set up user defined paths for temporary files in the QGIS version that I'm using (settings -> options -> systems). When I run code within QGIS3 the temporary files are saved in the indicated ...
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1answer
25 views

gdalnumeric.LoadFile() with temporary output from QGIS algorithm

I'm trying to access a previously created temporary raster output with gdalnumeric.LoadFile() to calculate some statistics. It seems to me that gdalnumeric.LoadFile() can only access a file through a ...
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0answers
34 views

Shapefile To svg to dxf and back to shapefile

I need to edit a complex vector polygon layer based on a raster layer. It will be a lot easier for me to do the drawings in an illustration software like Inkscape and then to import it back to QGIS. ...
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30 views

How to Open QFileDialog In QGIS 3 plugin?

i tried to open file dialog with Qgis Plugin its through argument 1 has unexpected type Error here My code # -*- coding: utf-8 -*- """ /**************************************************...
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1answer
62 views

Apply style to a layer in a geopackage using PyQGIS

I have a geopackage containing layers and styles stored, I need to assign one of the layers a style defined by its name. I have seen several examples but they use styles stored in external files and I ...
2
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1answer
34 views

Create Point based on location of minimum elevation inside a polygon in QGIS3

For QGIS3.0: Using DEMs, I am drawing polygons around depressions. Inside that polygon, I need to generate not only the minimum elevation value but the location that value was extracted from; this ...
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0answers
47 views

How can I align roads to follow hex bisection paths in QGIS?

I've created a hex grid and I would like to align and simplify each road such that each road segment has basically 2-3 vertices within each hex: Entry side (centered on the side it enters on) Center ...
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0answers
34 views

How to get a more refined and smooth DEM?

I have Two DEMs (Digital Elevation models) DEM (Image 1) - received from my institute DEM (Image 2) - downloaded from srtm Both DEMs have been styled similarly. But DEM (Image 1) looks better than ...
5
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1answer
1k views

Add PostGIS layer to QGIS via Python Console

How can I add a PostGIS layer to QGIS via the Python Console? With some server setups, especially with a large number of tables, it can be very slow to load the list of layers via the Browser or Data ...
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0answers
28 views

QGIS 3.10 - Field calculator expression running in Attribute Table and not in Processing Modeler

I use the Field Calculator in the Attributes table and run the operation : "FieldA" - "FieldB", where "FieldA" and "FieldB" are height distances in meter with a ...
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0answers
46 views

QGIS: Error when using Undo/Redo on layers loaded from PostgreSQL database

I am working with layers loaded from PostgreSQL(11.7)/PostGIS database to QGIS 3.10.7. When I try to undo/redo changes made on the layer it fails, sometimes during the undo and basically every time ...
1
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1answer
23 views

NMEA Data Feed into QGIS

We have a maritime simulator in our office we occasionally use for engineering studies...I was trying to figure out how to get a shape file of the path taken by the ship being driven into QGIS. Data ...
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0answers
14 views

Drawing polygon constant km around point in lat/lon coordinates in QGIS3.12

I have a set of points in lat/lon coordinates over Europe representing pixels from a satellite dataset. I know each pixel has size 10x10km. I want to draw a square polygon around each single pixel ...
4
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1answer
91 views

Distance between points along line

How do I determine the distance between points to the neighbor point that connected via the line(road)? In QGIS 3.8.3 I have tried v.distance and v.net.distance but they do not help. The line(roads) ...
2
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1answer
48 views

QGIS TIN interpolation - error in pixel size of output

When using the "TIN Interpolation" tool in QGIS 3.10, the output raster file doesn't keep the pixel size I specify. For example if I specify a pixel size of 1.0m, the output file actually has a pixel ...
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0answers
16 views

Generating UUID(unique ID) at joining points

I have road network (lines) and points (Address) . With the help of closestSegmentWithContext function, I join points to nearest lines in QGIS. Is there a way to to generate a unique ID at every ...
1
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1answer
237 views

Installing Python modules for QGIS3 on Mac?

I want to install some third-party Python modules for QGIS3 on Mac, however, I have no clue how to do it, since I am not so much familiar with different Python environments. Is there any similar ...
6
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1answer
454 views

Save QGIS project to PostgreSQL/PostGIS database using PyQGIS

I'm currently working on some code to automate the creation of a QGIS project from tables in a PostgreSQL DB. For info I'm working in QGIS 3.4. I'm almost there, but I'm stuck on one thing How do I ...
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0answers
56 views

Match up two polygon layers in QGIS

I have two polygon layers, one is from natural earth data (Administrative 1 division) and the other is a polygon layer with some historical regions in Europe. As you can see in the image attached ...
1
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1answer
193 views

QGIS SAGA “Kriging” tools doesn't work

I try out different methods of point interpolation for a digital terrain model. For this purpose I tried to run the "ordinary kriging tool" from the SAGA Tools with QGIS 2.18 and QGIS 3.2. When I run ...
2
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2answers
148 views

How to fix QGIS being extremely slow?

I am developing plugins and for some reason my QGIS keeps getting slower and slower. At first when I clicked on QGIS it opened right away, now it takes at least 2 minutes just to open and it also can ...
0
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1answer
125 views

Clip to mask layer not adhering to expected width and height following CRM and resolution changes

I am attempting to take a simple opentopo heightmap and carry out the following in QGIS 3.4.1 - Reproject to UTM 31N - Set cell size resolution to 5mtr - Clip to a shapefile polygon feature exactly ...
1
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1answer
36 views

Copy & Paste the styles of several layers to similar layers in an other project

I have a project with several layers and a specific styling for each one. In a similar project I have similar layers which need to be stlyed the same way. I could copy the style of one layer in my ...
1
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1answer
2k views

Writing PyQGIS script to modify layer (add field and fill it) inside QGIS?

I have the following PyQGIS script with QGIS 3 that tries to ask for a layer, add a new field in that layer and modify the value of this field. But the code doesn't work. I get either Seems there is ...
2
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1answer
136 views

Error while exporting geometry to CSV with MMQGIS

I am importing a DIVA-GIS shapefile into QGIS. It has a lot of polygons on it. My aim is to group different groups of polygons together and dissolve their internal boundaries so that I end up with ...
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0answers
20 views

How to include a tolerance when using QGIS topology checker

I'm using QGIS 3.14.3. The topology checker in this version doesn't seem to include a tolerance. I'm trying to relate points to lines by 'covered by' but keep getting errors.
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0answers
22 views

How to initialize the QGIS from standalone script?

I tried to initialize QGIS from a standalone script, but it's giving the error (find in an image). I reinstalled, but the same issue occurred. code: from qgis.core import * QgsApplication....
2
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1answer
176 views

QGIS not coming to foreground

I recently upgraded from QGIS 3.2 to 3.4 using the standalone installer (Windows 64 bit), and uninstalling 3.2 beforehand. When I open 3.4 it goes the background behind all my other open programs and ...
0
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1answer
19 views

GDAL Driver from QGIS 3 Raster Layer

How do I use python to find raster layer properties like The GDAL driver and/or description used to load a raster in QGIS For Example : for a Tif 'GTiff' and 'GeoTiff' or        for an ESRI Grid '...
0
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1answer
170 views

R.Viewshed Not Working

Getting the following error message when running r.viewshed Processing algorithm… Algorithm 'r.viewshed' starting… Input parameters: { '-b' : True, '-c' : True, '-e' : False, '-r' : False, '...
1
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2answers
161 views

Adding coordinates to attribute table

If I use the 'Add coordinates to point' it adds the coordinates to in the file, however splits the data into the amount of objects in the original file. If I try to add separate columns in the ...
0
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1answer
26 views

Get data type for a QGIS 3 RasterLayer

How do I use python to find raster layers data type The raster data type for a band like float32 or int16? I know you can use rasterlayer.dataType(1) but how do I then lookup returned integer (eg 6) ...
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0answers
28 views

Data layers with same coordinate system in QGIS 3.10 LTR are not aligning on basemap when redefining projection

I was able to get the data layers lined up with the basemap using EPSG:102004 - USA_Contiguous_Lambert_Conformal_Conic. However when I re-define the projection to EPSG: 2246 the coordinates are way ...
2
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1answer
33 views

Problem with photo displaying in QGIS 3.10

I would like to know how to display a photo in a image viewer with a featured action. I create a layer with 3 fields: id, leyenda and filepath. Filepath is the field where I put my photo.. Then I ...
1
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1answer
29 views

Error while clipping raster by mask layer

I am using QGIS 3.8 on Mac. When I tried to extract raster by mask layer, it gives following error and its been a while I am not able to fix this. "GDAL command output: /bin/sh: gdalwarp: command ...
0
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1answer
23 views

Zonal Statistics - polygons and rasters with different projections

I know that there are many many posts about this type of topic already, but all solutions did not work out for me so far. I have a shapefile with polygons, which is described here and can be ...
2
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2answers
72 views

QGIS update to 3.14 Pi

I try to update QGIS to 3.14 version with osgeo4w-setup-x86_64 but 3.14 does not appear in list. It only shows 3.12
2
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1answer
29 views

Columns order mixed up by style

I have a point layer for wich I've set the order of columns while using field calculator and Refactor fields instruments. But the order of colums is different when I'm choosing point by Identify ...
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0answers
22 views

QGIS 3 replace set of vertices with another set of vertices, like copy/paste

I have a layer that contains polygons that should be "topologically correct" if I understand that term correctly. The polygons should share vertices of adjacent polygons, allowing no gaps ...
1
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1answer
494 views

Toggle labels from toolbar in QGIS 3

I recall having a label-toggle button in the toolbar in earlier QGIS (2.x). If the selected layer had labels configured, then clicking this button would toggle their visibility off or on. The labels' ...
0
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0answers
31 views

Batch PyQGIS3 NDVI calculation yielding skewed outputs

In a previous post, I thought I'd cracked a problem running a script with a batch NDVI calculation on some 16bit unsigned ENVI .hdr data cubes: from qgis.analysis import QgsRasterCalculatorEntry, ...
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0answers
19 views

Error when EXPORTING Merged Raster with QGIS 3.14

I have been merging OS Open Data Terrain 50 asc files to create a single Geotiff file. I use Raster> Miscellaneous > Merge... This works flawlessly if in the Merged slot [Save to temporary file] ...

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