Questions tagged [qgis]

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

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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 ...
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Naming clipped layer according to the attributes of the mask layer in QGIS

I have calculated the dnbr for a fire season across a whole region, and I've clipped it using a mask. The mask is a layer of ground survey plot locations because I want to find out the dnbr for each ...
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Grouped "labels" for QGIS 3.0 Point Cluster styling?

I'm trying to make a cluster visualization of a vector point layer about trees with a few requirements: The clusters need to change depending on zoom level (solved) The clusters need to indicate how ...
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2 answers
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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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8 votes
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Regex_replace in the Field Calculator: unexpected duplication of replacement elements

After testing things out for a different question, I found something unexpected about the way regex_replace works in the Field Calculator, compared to PostgreSQL. The suggested insert ends up ...
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QGIS vector field marker not respecting map rotation

I’m working on a map the shows point displacement between two dates. These are survey benchmarks that are surveyed periodically to observe slope movement. Symbolizing this in QGIS is straight forward ...
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8 votes
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85 views

Does QGIS use data source-specific operations?

This may be a very basic question, but I couldn't find an appropriate answer. Does QGIS use data source specific operations where available and appropriate? For example, when using the Join attributes ...
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181 views

How to uncompress a file geodatabase with open-source tools?

At 3.10.4 I tried to load a FGDB polygon feature class, but it failed, with an "Invalid Data Source" error. I tried the load with both the Vector > Directory > ESRI FileGDB and Vector > Directory > ...
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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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8 votes
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981 views

Nearest neighbour joins for two geodataframes using KDtree from scipy/sklearn

I have a number of large geodataframes and I want to automate the implementation of a Nearest Neighbour function using a KDtree for more efficient processing. The process I want to achieve here is to ...
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Snap LineStrings considering direction in QGIS 3

I have 2 projected shape files: Roads (red) and public transit routes (blue): I want to snap the PT routes to the roads, but because of inaccurate marks sometimes the routes are snapped to the wrong ...
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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 ...
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8 votes
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827 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 ...
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248 views

Equal length dashed lines while using 'segments_to_lines' in QGIS

I want to create tapered lines with a dashed line stroke (to style intermittent streams). I followed this tutorial to create the taperered lines, basically using Geometry generator with the expression ...
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8 votes
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515 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 ...
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614 views

Setting up PyCharm CE 4 to work with PyQGIS library in Mac OS

I am trying to set up PyCharm to work with PyQGIS library. I am using PyCharm CE v4 and QGIS version 2.8 I have tried to implement the instructions of several posts like: http://osgeo-org.1560.x6....
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7 votes
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140 views

Printable Globe in QGIS

I'm trying to figure out how to use QGIS to print a map so that it can be wrapped around a sphere. I haven't found a projection that will display the map in a way similar to these. It sounds like ...
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7 votes
1 answer
142 views

GIF freezes when QGIS plugin runs

I have a QGIS plugin and would like to put loading GIF (spinner) somewhere in the Dialog Window. The problem is when I run the spinner with the following code and call next function, the spinner ...
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7 votes
0 answers
229 views

QGIS contextual menu overriding

I would like to override the default contextual menu in QGIS 3 in the ToC. I've created a class that inherit from QgsLayerTreeViewMenuProvider. from qgis.gui import QgsLayerTreeViewMenuProvider from ...
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  • 463
7 votes
1 answer
563 views

GRASS v.clean tool in QGIS gives empty output

I am trying to run v.clean in QGIS 3.10.7. I have a 2D LineString dataset saved in GPKG format and I want to run v.clean to clean up some messy topology. But whenever I run it, I get the same result - ...
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7 votes
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145 views

Filtering in QGIS attribute table 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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7 votes
1 answer
92 views

Counting upstream dams along river network in QGIS

I am working on QGIS. I have a river network where each segment is a line with ID from the upstream one (if any) and the downstream one (if any). I also have information on: location of dams location ...
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7 votes
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119 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 aggregate ...
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  • 101
7 votes
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531 views

How to create LineString geometry in QGIS3?

The default geometry type for a newly created line seems to be MultiLineString. It can be changed to LineString using the Multipart to Singleparts tool while saving in memory. However, once it is ...
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  • 181
7 votes
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267 views

QGIS plugin external libraries in plugin’s directory

I’m developing my first QGIS plugin and I have to use two external libraries not included in the default OSGeoW64 installation: Couchdb and Pandas. I would like to include those libraries in my ...
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7 votes
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978 views

Question marks ("?") in QGIS layer panel when using SVG markers defined with "Data defined override"

When using SVG marker symbols and set the path to SVG file via Data defined override the SVGs display well in the map canvas, but not in the layers panel (applies for QGIS 2.x and 3.x). SVG marker ...
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7 votes
0 answers
270 views

Identification of roof peaks on a Raster in Qgis

I am trying to map all the flat roofs of a city. After processing my data I have a huge raster with the zones that are flat (=1) and not flat (=0). I can overlap the roof polygons over this raster and ...
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  • 239
7 votes
0 answers
13k views

Creating in-line variable in field calculator of QGIS

I create new field based on other fields. For example; if "Field_A" is smaller than "Field_B", value of new field is 'A', otherwise it is 'B'. So I want to create new variable for ...
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7 votes
0 answers
697 views

QGIS Automatically Converts UTC Date-Time to Local?

I imported a WFS layer from a geoserver into QGIS and also into a web service that is based on Cesium. The geoserver fetches the data from Elastic search and serves it out as WFS. The date-time ...
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7 votes
0 answers
151 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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7 votes
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174 views

How to change the color ramp of a rule based styling in QGIS?

I use rule-based styling in QGIS, in order to do spatial quantile, computed in R. If I want to change the color ramp, I need to either: change every class color, or set graduated then change the color ...
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7 votes
1 answer
370 views

Topological editing of two different layers in QGIS

Is there a way to apply topological editing to move vertices between two coincident features that are not in the same layer? For example, if I have a crop land polygon coincident with a soil polygon (...
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  • 133
7 votes
0 answers
674 views

Using QGIS' "network protocol" to import data from OPeNDAP?

After looking at the OPeNDAP documentation I assumed I could import data into QGIS by downloading the .ascii file OPeNDAP generates. However the downloaded OPeNDAP .ascii doesn't seem to be compatible ...
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7 votes
0 answers
1k views

QGIS cannot open output layers

I have problem with QGIS 2.0.1. Everytime I run tool from SAGA or GRASS, I get exactly the same error, for example: Oooops! The following output layers could not be open Channel Network: /tmp/...
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7 votes
1 answer
350 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 ...
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  • 7,459
6 votes
0 answers
30 views

Exporting Geopackage converts milliseconds of QDateTime to zero

I use this solution to display actual QDateTime value with milliseconds in a temporary memory layer. And I use another solution to export as CSV the value including the millisecond value. But then, I ...
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6 votes
0 answers
24 views

Remember the last expanded property in QGIS Print Layout

While working with QGIS Print Layout, I usually set a property for an item (for example, "Position and Size" for "Map" item), then select another item and set a property. After ...
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6 votes
0 answers
74 views

Increase tolerance of QGIS processing tools

I have 2 line layers in QGIS 3.22.0 and I create a 10cm-buffer around line layer A (red) perform a difference of line layer B (blue) with the buffer of layer A (light red) As a result I get 1 ...
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6 votes
0 answers
70 views

QGIS service area except at intersections with vertices

I have a wastewater pipeline and a manhole layer. The current pipe layer is made of several lines between manholes (for example at every house connection, with no manhole at these locations). I want ...
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6 votes
0 answers
135 views

Time-Space aquarium with paths

I am trying to reproduce this kind of spatial representation with QGIS. It's a space-time aquarium where each line represents a path compared to time: It is a representation from the Time geography, ...
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  • 71
6 votes
1 answer
412 views

Working with remote QGIS server project files

I went into some troubles when making my first steps with QGIS server and I could not find an easy way to go. Some context My projects files (qgs/qgz) are on a remote server (Ubuntu based, headless, i....
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6 votes
0 answers
132 views

Performance-limits of QGIS expressions

I use quite often QGIS expressions and I am wondering how performant they are compared with other possibilities. In many cases, the same problem can be resolved using different approaches like using ...
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6 votes
0 answers
514 views

How to change QGIS 3 default encoding

When I import shapefile layers their encoding is System while the data is in UTF-8. How to change the default encoding to UTF-8? This question answer here " Is it possible to change default ...
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6 votes
0 answers
184 views

QGIS N:M relations - possibility to edit multiple features?

I have a working QGIS project with multiple relations and all is well until I try the Toggle multi edit mode for N:M relations. I'm working with QGIS 3.10+ (3.14.16) and Windows and PostGIS. Is it ...
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6 votes
0 answers
74 views

Why is QGIS holding references to layers that are not in layer list

I have a QGIS project, which has about 30 layers in the layer list. I removed one of the layers from the list, saved the project, closed QGIS. (The layer itself was from a Geopackage database, which ...
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  • 2,754
6 votes
1 answer
182 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 ...
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6 votes
1 answer
184 views

QGIS: data defined position of bar diagram

I am using QGIS to visualise communal water balances of different years as bar plots (QGIS 3.8). I have a point layer (communal area's centroids) with the balance values as attributes. I'd like to ...
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  • 143
6 votes
0 answers
76 views

Is it possible to make "Project Bookmarks" the default when adding a bookmark in QGIS?

Whenever I add a new bookmark in QGIS (3.14), I have to change the Saved in dropdown from User bookmarks to Project bookmarks. Is it possible to make Project the default? The User bookmark doesn't ...
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  • 1,776
6 votes
1 answer
91 views

Datum transformation in QGIS Server 3.10

I have a QGIS project that uses data stored in Web Mercator (epsg:3857) spatial reference system. The project itself has epsg:5514. To have a better precision I use one of datum transformations that ...
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  • 61
6 votes
0 answers
242 views

Getting layer id of processing step in QGIS graphical modeler for usage within aggregate() function

How can I get the layer name or layer id of the result of an processing algorithm within QGIS graphical modeler, so I can use aggregate() function in a later processing step? Is this somehow possible ...
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