Questions tagged [qgis]

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

7,393 questions with no upvoted or accepted answers
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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
52 views

QGIS Processing algorithm output

I am developing a plugin in QGIS using Python language. This plugin uses algorithms from Processing Toolbox and I save some results in the temporary folder assigning QgsProcessing.TEMPORARY_OUTPUT in ...
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29 views

Error message while running Strahler order for river delineation

I wanted to make river network using Strahler order in SAGA with filled DEM as the input, but there is an error message keep appearing: QGIS version: 3.14.0-Pi QGIS code revision: 9f7028fd23 Qt ...
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30 views

How to eradicate excess lines in a singly recorded polygonal line (road) network? QGIS 2.8

I'm a beginner in GIS software. I'm trying to create a road network shapefile within the reserve I work at. To do this, I've driven each and every road inside the property with my GPS app set to ...
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47 views

QGIS Exporting Line Direction Symbol from Labels

I have set up certain labels to show the Line Direction using the Line Direction Symbol in Label Formatting, with default < and > symbols. It works great, but I now want to export these symbols ...
4
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1answer
57 views

QGIS HTML labels only for objects visible on map

I'm printing QR-code that is generated on the fly in QGIS Print Composer. The URL to get the QR-code ist stored in a PostgreSQL database in the attribute-field "url". <img src = "[% &...
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24 views

Batch create multiple buffers with variable size around point

For a statistical analysis, I need to calculate some landscape properties in several (rectangular) sample areas, which vary in size (extent ranging from 10 by 10 to 500 by 500). These sample areas are ...
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23 views

Wrangling precision in QGIS with a hypothetical planet

I'm a tabletop roleplaying gamemaster wanting to use QGIS to help organize my notes according to place. GIS addresses my need to store notes and other data that may be anywhere from a few feet from ...
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32 views

QGIS 3 Dragging layer in table of content with keyboard

Sometimes it is hard to drag a layer with a mouse. Is there a way to drag a layer (сhange its position relative to other layers) in a QGIS 3 table of content using only the keyboard?
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78 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 ...
4
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1answer
45 views

Make QGIS use a conda virtual environment for python libraries

I wanted to install a plugin, but it requires scipy. Thus I realized that QGIS use the default python3 installation. I tried to launch it from a conda virtual environment, as advised in this related ...
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48 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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43 views

Interpolating Z at polyline vertices between known Zs

I have polyline strings with vertices of known elevation / z height and intermediate vertices with null/zero height. Known Zs are spread throughout the line. I'd like to be able to populate the z of ...
4
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1answer
32 views

Change black box around a Raster

Using the GDAL Georeferencer QGIS 3.10.10 I have georeferenced an old map, so now it is rotated a bit. The NoData fields for the "frame" are now black (RBG = 0,0,0). I would like to get rid ...
4
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1answer
49 views

Nearest neighbor distance in km over contiguous US

I have two sets of line features in QGIS (rivers & roads - I'd like to find the road segment nearest to each river segment & the distance between them in km) across the contiguous United ...
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114 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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50 views

Subclassing QgsMapToolDigitizeFeature

How does one subclass QgsMapToolDigitizeFeature? I'm trying to create a map tool in QGIS using Python. The tool will need to draw a polygon (and points and lines) in the same manner that QGIS does ...
4
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44 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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71 views

Sending requests including headers via PyQGIS by using QGIS Proxysettings

I am working on a plugin, where sending requests to an external server is part of the process. When using no proxy (like from my personal computer), this works just fine: isochrone_headers = {"...
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113 views

QGIS Layout: Expressing name of the map theme in a label

I am looking for the exact expression/code to make sure I can express the name of the map theme in label in my QGIS layout manager. The reason why is because I have a template with some variables that ...
4
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1answer
177 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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91 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
65 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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68 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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112 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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46 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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57 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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52 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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99 views

Joining non-contiguous polygons in QGIS

I am trying to "physically" join non-contiguous polygons of the same layer to form one (when the polygons are spaced less than 5m), without distorting the original shape. This is a building layer, ...
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118 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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80 views

Close gaps between some polygons, which are adjacent in reality

I have tens of thousands of polygons (farmer plots) which have been measured while on the fields. This has caused plenty of gaps between some polygons, which is not the reality. I would need to close ...
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118 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): ...
4
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1answer
689 views

Visualizing LOD2/citygml in QGIS

I`d like to find out if and how it is possible to visualize LoD2 data (source:https://www.opengeodata.nrw.de/produkte/geobasis/3d-gm/) in QGIS 3.4/Madeira. So far I managed to load them into the ...
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147 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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477 views

Data Plotly QGIS 3.10

I'm new with QGIS and Data Plotly and I have a problem with pie charts feature for Plotly. I load a shape in QGIS and I use it with Atlas to display a pie chart depending of the selected area on the ...
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248 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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230 views

Error with ROI Semi Automatic Classification Plugin QGIS 3.4

I have troubles for making ROI with SCP plugin in QGIS 3.4. I dowloaded some landsat images with the plugin and trying to create ROI. To do it, I made a Bandset with DOS1 atmospheric correction, ...
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0answers
693 views

GeoPDF export in QGIS requires GDAL 3, how do I get GDAL 3?

I would like to use the new GeoPDF export feature of QGIS 3.10. The changelog states that it requires GDAL 3. I have QGIS 3.10 installed on OS X from the binary installer. The export GeoPDF feature is ...
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234 views

QGIS geometry error:Hole lies outside shell

I am using QGIS 3.8 and I am using a layer from OSM of Tokyo city. The layer is consisted from many polygons and I have tried to merge it but I got error. This is how the original layer was look like:...
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0answers
74 views

Setting default raster statistics extent in QGIS?

I recently found the setting in QGIS to rescale raster symbology using the current extent, which is really handy (Layer styling > Min/Max Value Settings). My question is - can the default extent be ...
4
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0answers
112 views

Displaying images as part of multiattribute labels using QGIS

I would like to display images referenced in an attribute column as part of a multiattribute label, so that I can eventually print them with the map. I do not want to display geotagged images, since ...
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0answers
79 views

QGIS 3 3D Marker

In the 3D view I add 3d.obj files as Marker.works very well. Is it possible to add different 3D markers on different layers or categories. When I use 2 different layers with different obj files 3D ...
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781 views

Error using 'Clip raster by mask' in QGIS v3.8.2

I am attempting to clip a raster to a shapefile boundary (country boundary, 1 polygon) using the 'clip raster by mask' tool in QGIS v3.8.2. Both layers are in WGS84, so projection mismatch shouldn't ...
4
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1answer
305 views

Where did checkbox option in Points to Path tool go?

I made considerable use of the "Points to Paths" tool. I forgot which QGIS version I was using, but it was most likely 2.x, probably 2.14. According to my memory and notes the tool had a ...
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2answers
284 views

MODIS Fire Product tile conversion to GeoTIFF problem

I downloaded a tile (selected tile in the picture) from https://ladsweb.modaps.eosdis.nasa.gov/search/order/3/MOD14--6/2019-08-09/DB/Tile:H25V6 I used gdalinfo on the file. It's output is Driver: ...
4
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1answer
171 views

Query in QGIS is significantly slower, than in pgAdmin

So, I've a table in postgresql, that is joined to other spatial table. If I've run a simple query in pgAdmin, let's say SELECT * FROM table1 WHERE "area" > '5000' and it takes less, than 1s to ...
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0answers
64 views

QGIS export to PDF - rasterize only basemap layers but keep others as vectors

I am building my own map in QGIS 3.4 in which I created a basemap from ESRI satellite imagery and a ESRI hillshade overlay. On top I have several custom vector layers (country borders, city names etc.)...
4
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1answer
73 views

Automatically exchange QGIS layer datasources during project opening?

Do you know of any existing QGIS plugin that automatically exchanges layer datasources during opening of a Project? I would like to transparently switch our users from "PostGIS A" server to "PostGIS ...
4
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3answers
362 views

Reordering layers in GeoPackage and changing the default naming in QGIS?

I have successfully saved several layers in one GeoPackage in QGIS 3.8. This is how it looks like in DB manager: I found out that the ordering of the layers is somehow strange when loading the GPKG ...
4
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0answers
686 views

“Clip Raster by Mask Layer” produces zero values (and not Nodata) outside mask boundaries

This is my first question here. I have a big raster of the world's nighttime lights and want to clip it down to the Adm0 of a country: In order to do so, in QGIS 2.18 what I do is using the Clipper ...