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Questions tagged [qgis]

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

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12 votes
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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 ...
Nick_W's user avatar
  • 575
11 votes
2 answers
2k 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 ...
Gidget1's user avatar
  • 111
10 votes
0 answers
712 views

How to use a Spilhaus/ESRI:54099 projection in QGIS

I am trying to make a map using a Spilhaus projection, similar to the one implemented by Esri here. QGIS has ESRI:54099 WGS_1984_Spilhaus_Ocean_Map_in_Square in its list of available projections, ...
Ben's user avatar
  • 405
9 votes
0 answers
124 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 ...
Geotob's user avatar
  • 376
9 votes
1 answer
1k 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 - ...
wfgeo's user avatar
  • 3,598
9 votes
0 answers
1k 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 ...
Jack's user avatar
  • 91
9 votes
0 answers
872 views

Change from LineString to MultiLineString when saving layer edits in QGIS

In QGIS, when a user creates a new single part line in an open editing session for a “Multi-Line” SpatiaLite dataset, the QGIS data type is initially a “LineString”. But, when the user commits the ...
Philip Whitten's user avatar
8 votes
0 answers
149 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 ...
Kadir Şahbaz's user avatar
8 votes
0 answers
465 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 ...
TrsBar's user avatar
  • 523
8 votes
0 answers
1k 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 ...
Ending's user avatar
  • 555
8 votes
0 answers
2k 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 ...
Jochen Schwarze's user avatar
8 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", the value of the new field is 'A', otherwise it is 'B'. So I want to create a new ...
Kadir Şahbaz's user avatar
8 votes
0 answers
214 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 ...
Chau's user avatar
  • 4,490
8 votes
0 answers
582 views

Is it possible to link symbol fill colors between different geometry types in QGIS

I would like to link symbol colors between two layers of different geometry types (point and polygon). I have tried to save/load style and to copy/paste but I don't think its designed to work that way ...
Bill H's user avatar
  • 81
8 votes
0 answers
3k views

Can I use GeoJSON GeometryCollection in QGIS?

I want to create a GeoJSON that contains multiple geometries to be used in QGis later on. Now I red through the specs here: http://geojson.org/geojson-spec.html#geometrycollection When I simply copy ...
Yojimbo's user avatar
  • 393
8 votes
0 answers
654 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....
Javier's user avatar
  • 221
8 votes
1 answer
1k views

PostGIS sequence in QGIS not working

I have a Multipolygon-Layer stored in a PostgreSQL/PostGIS database. The primary key field 'gid' is SERIAL. When trying to add a new polygon in QGIS (LYON 2.12.1 on OSX El Capitan), the attributes ...
geom's user avatar
  • 1,296
7 votes
0 answers
172 views

How to change the Point Cluster circle symbol to a convex hull

I am using the expression presented by the user JGH to solve the question 'Point Clustering in QGIS, but values show a percentage and not count of points' This shows my example: As you can see I use ...
Ingrid Ingravida's user avatar
7 votes
1 answer
383 views

QGIS Model Designer: 'Algorithm is not available' and 'NoneType' object has no attribute 'displayName'

I am building a model to automate a process of generating points at street intersections. When I run the model, there is no output. Checking the error logs, I see this: 2022-04-26T10:55:36 WARNING ...
user200934's user avatar
7 votes
0 answers
344 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 ...
Enzo Baldini's user avatar
  • 2,337
7 votes
0 answers
375 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, ...
user188527's user avatar
7 votes
0 answers
133 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 ...
nr_aus's user avatar
  • 3,576
7 votes
1 answer
215 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 ...
RiversAnalysis's user avatar
7 votes
1 answer
703 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 ...
Dan Getz's user avatar
  • 311
7 votes
0 answers
1k 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 ...
Geert's user avatar
  • 143
7 votes
0 answers
333 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 ...
Edoardo Pessina's user avatar
7 votes
0 answers
352 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 ...
maevad01's user avatar
  • 251
7 votes
0 answers
672 views

Is there a specific tool to globally manage visibility/theme in QGIS?

In short : I'm looking for a Visibility Manager (QGIS 2.18) ou Theme Manager (3.0). I couldn't find it in the QGIS plugin list or in different methods on gis.stack. Maybe I missed it and maybe it ...
gisnside's user avatar
  • 7,858
7 votes
0 answers
4k views

When does a QGIS .qix spatial index of a shapefile need to be re-created?

I understand the basics of spatial indexes but would like to understand when exactly a spatial index would need to be re-created or updated? The reason I ask is because when a folder was moved to a ...
AWGIS's user avatar
  • 3,230
7 votes
0 answers
177 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 ...
Stev_k's user avatar
  • 6,719
7 votes
1 answer
286 views

Loading vector layers from database/ schema using login username and password in QGIS?

I have a QGIS setup with a PostgreSQL / PostGIS database on a server and multiple clients. I have created schemas in the database for each user. With a username password combination, each user is ...
Ganesh Nagarajan's user avatar
7 votes
0 answers
2k views

Emerging hotspot analysis (space-time patterns) in QGIS

I worked with crime data a while ago and was really impressed by the possibility in ArcGIS to detect significant hotspots and their development over time (Emerging hotspot analysis). Does anybody ...
marc_mk's user avatar
  • 139
7 votes
0 answers
1k views

QGIS plugins not installing

I'm trying to install plugins on a fresh install of QGIS 2.18.12. I can connect to the plugins repository but trying to install any plugin fails with the error message: Failed to unzip plugin package....
Oliver Burdekin's user avatar
7 votes
0 answers
1k 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. ...
newGIS's user avatar
  • 4,072
7 votes
0 answers
1k views

Import Pandas or any Python module into QGIS internal Python

(Also asked in stack overflow - https://stackoverflow.com/questions/43244062/import-pandas-or-any-python-module-into-qgis-internal-python ) I am developing a plugin for the current LTR version of ...
jberrio's user avatar
  • 796
7 votes
0 answers
607 views

How to use pgRouting together with Django?

I am using pgRouting together with QGIS. Now I want to convert everything into a web-solution. I decided to use Django for that. Creating the data-model and receiving geographical data from the ...
AndreasK's user avatar
  • 1,235
7 votes
0 answers
923 views

PDF looks different from print composer

When I create a map in print composer the map looks exactly how I want it, but when I save it as a PDF some of the sympbols have changed. Note the roads are still visible in the PDF but some have ...
Val's user avatar
  • 71
7 votes
0 answers
467 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 ...
TalL's user avatar
  • 171
7 votes
0 answers
691 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 ...
cstroem's user avatar
  • 71
7 votes
1 answer
479 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 (...
RachelW's user avatar
  • 153
7 votes
0 answers
821 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 ...
Chris Kar's user avatar
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/...
Ondrej Berka's user avatar
7 votes
1 answer
1k 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 ...
Tomas's user avatar
  • 1,252
7 votes
1 answer
392 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 ...
she_weeds's user avatar
  • 12.6k
7 votes
1 answer
152 views

How to change the default symbology units of measure?

The default QGIS symbology unit of measure is millimeters (see highlighted screenshot below). This is true for both the main map display and for Print Layouts. The default millimeter setting can be ...
Stu Smith's user avatar
  • 8,160
6 votes
0 answers
77 views

Get rotation and scale of picture after georeferencing using QGIS

How can I access the rotation and scaling information, that is visible during the georeferencing process in QGIS (see yellow marked text in the picture), after the georeferencing is completed and the ...
automatikz's user avatar
6 votes
1 answer
139 views

QGIS doesn't truncate labels of point features in print layout

I'm trying to create a map that is separated into two pages (say, a A3 layout). I want them to be exactly the same except of the range they cover, so I can later combine them into one larger map (A2). ...
Frank Wang's user avatar
6 votes
0 answers
249 views

Transfer QGIS form from Drag and Drop Designer to QT

I want to take the form designed using the drag and drop designer in QGIS, into Qt Designer to modify it further and then bring it back into QGIS. Is this possible? As per Saving QGIS form design ...
GeorgeC's user avatar
  • 8,238
6 votes
0 answers
682 views

QGIS Graphical Modeler - How to query features in algorithm output?

I have a simple graphical model that uses a Field calculator to build a URL by concatenating strings in 3 fields of its input layer. This URL should be fed into the Download File algorithm using the ...
Matt's user avatar
  • 17.4k
6 votes
0 answers
92 views

QGIS: group labels from different lines below each other instead side by side

I have the following problem. I have a Linestring layer in QGIS. There are multiple lines drawn, sometimes overlapping each other. QGIS shows the label of the different lines next to each other. (...
André's user avatar
  • 357

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