Questions tagged [qgis]

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

5,826 questions with no upvoted or accepted answers
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11
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263 views

When using QGIS join by location, how does QGIS determine the first located feature option?

I have used QGIS process 'join attributes by location' in one of the models I have built and I have now been asked to explain in detail exactly how the model is determining the results. I am using it ...
11
votes
0answers
474 views

Accessing existing instance of QGIS from stand-alone python script

For my own data analysis pipeline, I am running a split screen setup with iPython notebooks on one side, generating variables from source data, pushing them to a CSV file which QGIS then reads/joins ...
8
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0answers
80 views

Is there a way to create quadrilaterals buffers around polygons in QGIS?

For a little map project of mine, I need to create quadrilaterals around a polygon feature based on the bisected angles of the vertices of that feature. Here is an example: Is it possible to automate ...
8
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0answers
122 views

QGIS Print Layout - Rotation of Grid Coordinates to match map rotation

I have a layout in QGIS where 3 map views are rotated to 35 deg. The grids automatically rotate to match the maps rotation, however the labels do not. Does anyone know a way to make the coordinate ...
8
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0answers
299 views

Point cluster symbology for different categories without overlapping symbols

I'm trying to visualize crimes based on if the crime happened during day or night time. I've tried using the point displacement tool but I'm not satisfied with the results because the readability for ...
8
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0answers
181 views

Open QGIS project files in exclusive mode / alert if project file already in use

I have QGIS-Project-Files saved to a network drive and was wondering if it is possible to warn users that a project file is already opened by an other user to prevent concurrent editing of the same ...
8
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0answers
900 views

How to digitize in stream mode in QGIS, using a tablet?

How to digitize in stream mode in Qgis, using a wacom cintiq tablet? freehand it's no use. i need something like MNDR stream digitizing extension for arcview 3.x, which allows continuous tracing, ...
7
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0answers
178 views

QGIS can't load geometryless WFS tables published with QGIS Server

I created a QGIS 3.6 project on Windows Server 2016 x64 with two PostGIS layers: Layer A: Points Layer B: Datatable (No geometries) and configured QGIS Server options on the project like this: Now ...
7
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0answers
152 views

Working with QGIS 3 with styles stored in spatialite database

I am working in QGIS 3.4 with a geopackage file (SQLite database) containing orography information (points, lines and polygons). In QGIS, I have defined by hand a style for every layer in geopackage (...
7
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0answers
146 views

Processing post-execution script hook to clear scratch layers?

I've been cobbling together some Processing scripts for QGIS 2.18 (I'm not a fan of QGIS 3 scripts), and I keep running into one particular problem: my script creates a lot of scratch layers and they ...
7
votes
1answer
882 views

Editing Layout-Items after loading a QPT-Template in QGIS 3 with Python

I am facing a problem with the new Layout API while implementing a plugin for QGIS 3. Starting point is a layout template in qpt-Format, which contains different elements like (attribute) tables, map, ...
7
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0answers
178 views

When moving a feature in QGIS, is there a way to nudge it rather than use the mouse?

I need to move a lot of features (polygons) in QGIS to fit a newly Georeferenced scanned map that is slightly asymmetrically distorted. This is fine as it is just to provide a print copy. I end up ...
7
votes
1answer
505 views

Display pictures stored as bytea in postgresql column in qgis

does someone knows a possibility to visualize in a bytea column saved photos of a postgresql database in qgis? I would like to store pictures directly into the database, not just the link/ url.
7
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0answers
1k views

How do I export a 16-bit image from QGIS?

Could someone explain how to export from QGIS a 16bit image. I have imported data and coloured it as I want, but need to export it as a 16bit image, as 8bit is giving a terracing effect.I believe I ...
7
votes
1answer
111 views

Show Symbol (e.g. City-Marker) only when an associated label can be displayed

I'm building a map for a certain region with many cities to be displayed. Some of the smaller cities should only be displayed if they don't overlay bigger cities. While the labels of the smaller ...
7
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0answers
2k views

Rasterize shapefile using another raster's size and resolution

Rasterizing a vector (shp) I face the following problem: I want my output file (the rasterized vector) to have the same resolution and dimensions as an existing raster. If I understand the interface ...
6
votes
1answer
86 views

Merge/join only the lines which are snapped to vertices in QGIS

I have polygons drawn with AutoCAD as Mline (Multiline type) which are rendered in QGIS as 8 segments for each feature. An example of one selected feature is shown in the picture below: I want to ...
6
votes
0answers
152 views

Using Layer Parameter variables in Field Calculator within QGIS Model?

If I define a Vector Layer as an input parameter to a QGIS model, then the parameter name is exposed as a variable in a Field Calculator within the model, however I am unable to use this variable as I ...
6
votes
1answer
215 views

Spatialite KNN view in QGIS

My task is to calculate the average ground survey level for each tree in my dataset, using the 3 closest survey points (optionally within a 3m radius of the tree). I want to write this in a Spatial ...
6
votes
1answer
2k views

How to use MMQGIS hub lines tool in QGIS?

I am trying to connect source and destination points with the hub lines tool in mmqgis. I have gone through the other posts on this subject but couldn't figure out what I am doing wrong. I have ...
5
votes
0answers
193 views

Loading multiple shapefiles in GeoDjango?

I have 3 three shapefiles and would like to upload all of them and project the result in GeoDjango admin. a) state.shp (for the shape of a state) b) boundary.shp (to identify a specific portion in ...
5
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0answers
398 views

Splitting polygon into equal area's polygons in QGIS 3.6?

There is a plugin in QGIS 2.18 called 'Polygon Divider' which divides an irregular polygon into smaller equal area's polygons of a specified/custom sized but in QGIS 3.x version there is no 'Polygon ...
5
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0answers
532 views

How to use ATOM FEED Data in QGIS 3.6.1?

I would like to know how I can work with ATOM FEED Data in QGIS. In ealier QGIS versions this worked with the Plugin "INSPIRE ATOM Client", but this Plugin doesn't work in the current version. An ...
5
votes
1answer
96 views

Nested rules in QGIS 2.18

I work with QGIS 2.18. I have a polygon shapefile with two atrributes: id (unique for each polygon) and type. I visualize the shapefile using the "type" attribute, but I would like to add a nested ...
5
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0answers
57 views

Referencing an output in an expression in process modeler

In the process modeler, I'd like to reference an output of a previous step as one of the parameters of an algorithm. In this case, the previous step was clipping a large raster and I want to use the ...
5
votes
0answers
194 views

Cumulative value/cost along shortest distance roads in QGIS

I have a road network linking multiple (ca 1830) agricultural production regions to several ports (ca 12). (lines in the pic below are roads, small black dots centroids for producing regions and ...
5
votes
0answers
193 views

Old .qml style (vector-polygons) from QGIS 2.18 in QGIS 3.4

I have a .qml polygon style file created with QGIS 2.18. It works to import until Version 3.2 without problem. But in 3.4 the style is loaded, but not applied/visualized. The Polygons dissappear ...
5
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0answers
337 views

Fixed QGIS layer symbol size in layer legend

When a layer symbol is defined with map units or "meters at scale" unit, it is sometimes shown in the legend at a very small scale, preventing to see the details. Or if we zoom in the map, the legend ...
5
votes
0answers
381 views

Add private plugin repository to QGIS 3.4

I want to add a repository to my QGIS 3.4 which is on a private server. The repository contains all files needed (plugin.xml and metadata.txt for example) and has the structure as described here: Is ...
5
votes
1answer
631 views

Enabling QGIS Official Plugin Repository in the 3.4.1 Version?

I am using QGIS version 3.4.1. Recently, I cannot install new plugins. I have looked in the plugin setting. It seems that the link is blocked. The address is "https://plugins.qgis.org/plugins/plugins....
5
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0answers
497 views

QGIS 3.4.1 Extensions Repository not available

In my QGIS 3.4.1 installation (Windows 10) the extensions repository says "unavailable", like in this older post: Why I can't install plugins?. I already added the repository with "HTTP" instead of "...
5
votes
0answers
180 views

Setting grid in QGIS that automatically adjust its intervals?

I am setting a template for multiple maps in QGIS 3 Layout and i was wondering if there is a way of automatically adjusting the grid's interval as a function of the scale of the map? I did a bit of ...
5
votes
1answer
252 views

Change data source encoding of GetFeatureInfo response for a WMS in QGIS

How do I change the data source encoding of the GetFeatureInfo Request of a WMS-Layer in QGIS 2.18.x/3.x? I can't find any setting to handle the encoding. I need UTF-8 encoding for special characters ...
5
votes
0answers
77 views

Using the height of river to approximate its extreme flood boundaries - terrain analysis in QGIS?

Using QGIS I'm trying to analyse an area/DEM with this criteria: - heights 10 meter above the river-centerline in both sides of river. I can do it with the calculation of contours (2m) from DEM and ...
5
votes
0answers
662 views

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 ...
5
votes
0answers
235 views

Using transform function in QGIS layer geometry generator?

I'm trying to use the following expression in the geometry generator in a QGIS layer to show a 1-mi boundary around points: buffer(transform($geometry, 'EPSG:4326', 'EPSG:2877'), 5280) However, the ...
5
votes
2answers
174 views

Automatically moving along columns within a layer as moved to the next item in a QGIS Atlas?

My problem is quite hard to explain, I have attached some images to help illustrate my issue. I want to produce a large number of maps which overlap in geographic area. Currently my data is arranged ...
5
votes
0answers
148 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 ...
5
votes
0answers
174 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 ...
5
votes
1answer
421 views

how to buffer a line with varying distances associated with directional quadrant with open source GIS?

I would like to buffer a set of lines with different distances to the NW, SW, SE, and NE. I have the distances stored in four attribute fields that correspond to the direction the buffer should be ...
5
votes
0answers
457 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. ...
5
votes
0answers
134 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 ...
5
votes
0answers
118 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 ...
5
votes
1answer
143 views

Merge line shapefiles into a single shapefile while maintaining integrity of lines that overlap?

I have over 300 line shapefiles and I want to merge these files into a single shapefile. I have used merge tool in QGIS, but this tool merges overlapping features into a single feature. I, however, ...
5
votes
0answers
307 views

QGIS/Spatialite cluster analysis with density

beginner here I am trying to analyse a large set of points (2 millions) over a set of polygons (3000), and particularly find clusters of points. Doing it in QGIS was taking too long/crashing the ...
5
votes
0answers
100 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 ...
5
votes
0answers
364 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 ...
5
votes
0answers
364 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 ...
5
votes
0answers
274 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 ...
5
votes
0answers
754 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 ...