Questions tagged [qgis]

QGIS is a cross-platform GIS application licensed under the GNU General Public License.

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Error running r.thin in QGIS

I get the following error when running r.thin: Traceback (most recent call last): File "C:/PROGRA~4/QGIS3/apps/qgis/./python/plugins\processing\algs\grass7\Grass7Algorithm.py", line 395, in ...
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104 views

Speed up identify in QGIS

I have just transferred my Postgis database onto an RDS server, and there is a bit of a performance hit when using the Identify tool in QGIS (3) compared to localhost. I presume this is mostly network ...
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204 views

Voronoi Polygon Algorithm seems to exclude a Point from processing

I am using the QGIS (2.8.1) Voronoi Polygons Algorithm on a point shapefile. See image below, the red triangles are the points I am using. The resulting polygons miss a part (around HP87). Any ...
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247 views

What bin value does QGis Histogram uses?

I have some single-band rasters (NDVI) on Qgis, for which I can obtain their distribution histogram by going to Right-click > Properties > Histogram Tab > Compute Histogram. This is an ...
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176 views

show relations between polygons by highlighting polygons

Is it possible to show relations (for example traffic flow) between polygons (for example counties) by highlighting related polygons by doing a query on a start polygon using QGIS? Here is an ...
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189 views

Value relation autocompletion and dropdown menu in QGIS?

I use a value relation widget which is connected to a list of streets. If I tick "use completer" I can use the autocompletion but the dropdown menu disappear. The dropdown menu appears again only if ...
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557 views

Creating text buffer in legend QGIS 2.18?

I work with this polygon layer and this is my map composer: I used the labels with Text Buffer (yellow and red), and I try to find how I can make the same text buffer in the layer name in the legend. ...
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145 views

Creating Viewsheds in Graphic Modeler

I am trying to use Graphic Modeler to run viewsheds. As I can’t appear to use the Viewshed Analysis plugin tool in Graphic Modeler and I instead need to use the GRASS command r.viewshed. I am ...
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122 views

Issues with atlas generator and labelling across maps/images

I have a lot of layers in my project and I am trying to use the atlas generator in the print composer to create a tiled map. Some of the layers have labels which have different configurations with ...
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4k views

K-Means clustering in QGIS (Attribute based clustering)

In the 2.18.4 and 2.18.5 version of QGIS K-means clustering was moved to a plugin called 'Attribute based clustering'. However, I am working with a virtual raster dataset (vrt.) and the current ...
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107 views

Selecting minimum number of neighbouring polygons required to give a fixed total area

I have a polygon layer. I would like to select the minimum number of neighbouring polygons to give a total area greater than a fixed value. In reality the polygons are land parcels and I would like to ...
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430 views

What's the fastest way to convert large csvs to point shapefile

I'm working in QGIS, and my current method to change csvs to shapefiles is to import them to QGIS, right click and save as shapefile. For large CSVs (over 100 million rows) it can take quite some time ...
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400 views

QGIS Referencer: Tranformed Failed

I'm using a new install of QGIS 2.18.2 on an iMac running OSX 10.10.5. I create a new project. I use the OpenLayers plugin to show an OSM background of a part of Mayfair in London. I now use the ...
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303 views

QGIS doesn't handle PostGis connection resets?

I'm highly frustrated by the fact that if I leave the database alone for a more than a few minutes, I can no longer insert new lines. If I restart QGIS, everything goes back to normal. I believe this ...
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770 views

Build QGIS 2.16.3 on windows 7 SP1 x64

I'm trying to learn how to build QGIS from source perfectly with windows 7 x64 to adapt QGIS for a urban planing. But I get plenty of errors. Until now this is what I'm doing: PART1: VISUAL STUDIO ...
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498 views

QGIS Align Rasters how to retain pixel values?

I am attempting to align and then merge a number of rasters of the same resolution and extent, but where the pixels are slightly misaligned (creating small gaps when merged). This works fine using the ...
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1k views

QGIS: Release file lock on file used in a processing algorithm at the end of script

I am using runalg (qgis:joinattributesbylocation) on two QgsVectorLayer objects. At the end of my script I'm trying to delete all the files created during the script. I can delete everything except ...
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473 views

Insert sequential row and column values automatically into a fishnet dataset

I have a grid that has about 30 rows with approx 15 columns each. I want to label them as A1,A2,B1,B2 etc (Alphabet row, integer is column). Is there any way to do this programatically? There is no ...
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564 views

How to specify TIME parameter in URL for WMS-T server in QGIS?

Does anyone know how to specify the time parameter for accessing data through a WMS-T server in QGIS? I am trying to access fire data from FIRMS web server :(https://firms.modaps.eosdis.nasa.gov/web-...
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2answers
2k views

How to eliminate polygon overlap areas in QGIS?

Is there a way to remove polygon overlaps within the same layer using QGIS, preferably removing the overlap area of the biggest polygon (having the greatest surface)? All of my polygons are in the ...
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2answers
6k views

WindowsError: [Error 32] The process cannot access the file because it is being used by another process

I am reading images (through Python) and do something. These images are placed in a temporary file, through: tf = tempfile.mkdtemp(filename) I use gdal to read the images (short part of code): ... ...
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446 views

Is there a tool that shows dimensions during editing?

Is there a plugin or tool providing following functionality: I select 2 points (or vertices) - it shows the length between this points. When I edit the point (or move vertex) the length automatically ...
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897 views

Print Composer Template produces empty map?

I have a print composer template which I'm trying to populate with different subset queries from a CSV-derived vector layer using the Python API. However, all the output PDFs contain everything except ...
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603 views

Can extracting raster values work in polygons' CRS without raster resampling?

I am trying to extract raster values using polygon layer with different CRS. Raster is in WGS84 (EPSG:4326) and the polygons in UTM (EPSG:23031). 1. If I want to work in the projection of the ...
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670 views

How to debug Quantum GIS PlugIn Visual Studio DLL?

I have developed a Quantum GIS plugin layer using Microsoft Visual studio and placed it in my plugins folder of my customized QGIS application. I now intend to debug the DLL using Microsoft Studio. ...
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1answer
1k views

QGIS GRASS Processing Not Working on MacOS?

Recently upgraded to QGIS3 (3.0.2) for MacOS (High Sierra) and encountered GRASS (7.2.2) issues. Tried adding a custom variable and now when running GRASS algorithms (e.g. r.reclass) I get the ...
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30 views

Catgorizing label customization in QGIS 3x

Good afternoon, I need to set the different font size and different colour for my text string, which appears in the QGIS (label). I found some solution here: QGIS - When labeling, how can i set ...
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1answer
40 views

Maximum character length in Well Known Text for QGIS

Is there a maximum limit of characters in an Well Known Text (WKT) that allowed by QGIS Desktop?
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74 views

+0-180 degrees of mesh layer are displaying as horizontal lines [QGIS]

I have been trying to display weather data from ECMWF in QGIS on top of a base map, but half of the heatmap rendered from the mesh layer (imported via grib) displays as straight horizontal lines. I ...
4
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1answer
51 views

Measuring distances on custom ellipsoid

I'm trying to set up a QGIS project for creating a map of a fictional planet smaller than Earth. See here for a helpful question that doesn't quite touch on what I'm trying to accomplish (I don't mind ...
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50 views

Strange shapes and lines while importing shapefile

I am trying to add a Shapefile over the top of my map of Australia showing the extent of native grasslands. However every time I add it all these extra lines and shapes appear over the top of the ...
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35 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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56 views

Filtering in QGIS similar to dropdown in Excel

I have a large amount of point data that has so far been managed in an Excel list. In the future, these should be shown in QGIS. To convince colleagues of this, I am looking for a way to make ...
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57 views

Creating child entries in QGIS form with Spatialite many-to-many relationship

I am trying to reproduce the example from Introducing many-to-many (N-M) relations using Spatialite. Creating the tables and the relations works fine, but when I try to create a child element in a ...
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38 views

QGIS plugins for creating circular route on footpath network

I'm looking for a way to create random circular walks of a specified distance from a given point. The end result will be similar to https://routeshuffle.com/ and http://www.routeloops.com/, but along ...
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45 views

QGIS processing tools - saving/exporting graph

I just tried QGIS processing tools for the first time. When using shortest path search for the first time, the algorithm is building a path graph (of course). However, the graph is never re-used. ...
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62 views

Clustering without aggregation with QGIS Point Displacement

I've seen the following map on twitter and am looking to create the same effect for point displacement. I'm familiar with grid and circle point displacement as well as with clusters point to ...
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69 views

Open multiple QGIS projects via PyQGIS simultaneously in different threads

I'm writing a standalone PyQGIS application. When the method qgis() is called in a new thread, it's supposed to open a QGIS project (with one layer in it) and close it again: from concurrent.futures....
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86 views

Does the projection of a PostGIS table affect the rendering speed in QGIS

I am interested to know whether changing the projection of a PostGIS table will affect the rending speed when viewing it in QGIS. I have two layers coming from QGIS which are exactly the same and ...
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2answers
78 views

Why is a vertical polygon defined by WKT PolygonZ invalid?

Can you tell me, why this PolygonZ is invalid? PolygonZ ((409662 5317369 285, 409662 5317377 285, 409662 5317377 302, 409662 5317369 302, 409662 5317369 285)) The polygon is completely vertical, but ...
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40 views

Gdalwarp fails to properly reproject to custom projection

I am trying to reproject my tif file to custom EPSG:3857 projection. Input file picture + gdalinfo: Driver: GTiff/GeoTIFF Files: shd_120arcsec.tif shd_120arcsec.tif.aux.xml Size is 10800, 5100 ...
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73 views

How to calculate the distance between polygons and polygons (or polygons and lines) in QGIS?

I'm new to working with GIS data and QGIS. I'm trying to find an efficient way to measure/calculate the width of streets in a city. I have two datasets: buildings (polygons) and streets (lines). I'm ...
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88 views

Snap geometry/polygon to grid with minimum distortion

I am working on a project to transform polygons given in a pre-defined precision to a lesser precision, which I think is equivalent to snap them to a fixed spacing grid. For example, in the example ...
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52 views

Automatically snap lines at angles when offsetting

I used the geometry generator to offset lines. offset_curve($geometry,"offset") Is there a way to get the lines automatically snapped at angles when they are connected? I can use the rendering ...
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174 views

Is it possible to rename a table column with an expression in the field calcultor of QGIS?

I want to be able to rename a few column names with an expression in the field calculator in order to be able reproduce this action with the QGIS graphical modeler. I tried to do this with the ...
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0answers
88 views

GIS proj pipeline

I would like to create a custom projection in QGIS 3.10. It is a local stereo and the reprojection between WGS84 and the local stereo uses proj pipeline. For example in cs2cs it is (which works well): ...
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83 views

Using Geometry by Expression tool to make set of lines in QGIS

I am using QGIS 3.x. I am trying to make a set of lines that are 50m to 2000m, at 50 meter intervals (eg: line 1 is 50m, line 2 is 100m, line 3 is 150m, etc). I did it manually using the Advanced ...
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79 views

Showing labels as they will be printed/exported in my print layout?

I set up a print layout for a map I want to print in QGIS. Some of my layers have labels on them. When I zoom in and out in the screen, without changing anything else on the print layout, some labels ...
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172 views

Styling the legend in QGIS with line layer

Working on QGIS 3.4.13. I have a vector line layer, there are rivers. I put a rule based symbology with two categories and different scale max / min for each category. I want to put style for the ...
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152 views

QGIS 3: Set custom project variables with input dialog

I am using QGIS 3.10.0 and Windows 10. I have a project where I want the user to define custom project variables. I want to make this user friendly, I don't want the user to need to open the project ...