Questions tagged [qgis]

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

5,745 questions with no upvoted or accepted answers
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11
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452 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 ...
10
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0answers
231 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 ...
8
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0answers
98 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
883 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
169 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
127 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
votes
0answers
143 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
828 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
votes
0answers
291 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 ...
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
97 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
0answers
140 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
205 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
0answers
174 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 ...
6
votes
1answer
481 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.
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
177 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
votes
0answers
440 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
0answers
56 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
179 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
180 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
votes
0answers
307 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
355 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
583 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
votes
0answers
481 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
164 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
240 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
74 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
384 views

Qgis 3.0 and Qt 5.10 problems

I installed Girona on Ubuntu 17.10 and it never worked for me. I just updated Ubuntu 18.04 LTS and Qgis displays the following message: Traceback (most recent call last): File "", line 1, ...
5
votes
0answers
648 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
475 views

Calculating average pixel value for each band across multiple raster layers?

I have a set of raster files that are essentially data sets of precipitation across a region. I have multiple raster files that are the outputs of different climate models. Each pixel in the raster ...
5
votes
0answers
224 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
168 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
142 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
169 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
408 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
447 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
133 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
142 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
300 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
361 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
269 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
750 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 ...
5
votes
0answers
449 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 ...
5
votes
0answers
1k views

How to join segments of a line in QGIS?

I have lots of different lines composed of hundreds of segments in a Shapefile. I would like to join them spatially where every start (or end) point of a segment correspond exactly (or within a range ...
5
votes
2answers
627 views

Using Check Geometries plugin for polygons in QGIS?

I've a few hundred polygon features with many duplicate nodes, gaps, overlaps and other geometry errors. Fixing all errors seems to be quite tricky. I had to run the duplicate nodes check twice to fix ...
5
votes
0answers
453 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 ...