Questions tagged [qgis]

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

5,415 questions with no upvoted or accepted answers
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9
votes
0answers
406 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
votes
0answers
159 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 ...
7
votes
2answers
653 views

Using QField with Multi-User Access also Offline?

I got 10-20 QGIS-Users which edit all one Project online and offline. Sometimes they do it at the same time. Until now we only used QGisDesktop with a PostGis Database stored in QGIS Cloud(50MB ...
6
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0answers
142 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 ...
6
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0answers
133 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 ...
6
votes
1answer
621 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, ...
6
votes
0answers
250 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 ...
6
votes
1answer
177 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
1k views

Creating polygon elevation contours?

I'd like to create polygon shapefiles to communicate elevation information on regional maps. I find these draped over a hill shade layer provide one of the best base maps. I can tell some ...
6
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0answers
149 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
433 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
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0answers
417 views

What are the considerations for choosing between WKT and WKB geometries?

There are many questions & answers here addressing how to convert between WKT and WKB geometries, and about the specifications or implementation details. But what are the considerations for ...
6
votes
2answers
214 views

Plotting a hyperbola, or, solving spherical triangles

I am trying to create a GeoJSON path containing lines of hyperbola, in order to recreate Decca Navigator charts in QGIS, something like this: The chart has nine lines of hyperbola plotted between ...
6
votes
0answers
86 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 ...
6
votes
0answers
819 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, ...
6
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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
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
1answer
144 views

QGIS- Model works on single layer execution, errors out when run as batch

I have a pretty simple model in QGIS that I am trying to use as a batch process. The model takes a line shapefile input, creates a temporary buffer, extracts by location using that created buffer, and ...
5
votes
0answers
150 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
70 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 (...
5
votes
0answers
51 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
107 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
65 views

Offline editing slides the attribute data over one column and ads an “fid” column

My QGIS 3.4 Madeira project is attached to a PostGIS database (Azure) and looks good. It contains two layers, one with points and one with polylines. Each item in the Pointz layer has about ten ...
5
votes
0answers
134 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
285 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
312 views

Creating Groups of points based on proximity in QGIS?

I have a dataset with around 900 points and I want to cluster them into groups of 44 based on proximity. Is this possible in QGIS? I have tried to use the convex hull tool with no success.
5
votes
1answer
203 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
66 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
1answer
144 views

QGIS Legend multiple name for one shapefile using styles

I am using styles and presets in QGIS to display the same shapefile on various composers. The shapefile is representing townships with several fields such as population density, length of water supply ...
5
votes
0answers
346 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
630 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
390 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
2answers
151 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
131 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
162 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
0answers
355 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
132 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
114 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
124 views

How do I 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
287 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
97 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
344 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
736 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
435 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
440 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 ...
5
votes
0answers
884 views

Is it possible to do parallel processing in GDAL and QGIS?

It seems like processing a large raster dataset in QGIS can cause a crash, for example in QGIS failing to complete clip or intersect and crash dump in qgis. Is it possible to use GDAL parallel ...
5
votes
0answers
309 views

QGIS modeler - use input filename in output filename

I need to use the input filename in the output filename in a QGIS model. I have spent a couple of hours trying to find a solution but can't. If the input is contourXY.tab and I want output to be \...
5
votes
0answers
436 views

Is there a tool that shows dimensions during editing?

Is there a plugin or tool providing following functionality: I select 2 points (or vertices) - it shows the length between this points When i edit the point (or move vertex) the length automatically ...
5
votes
0answers
243 views

How to calculate radius of curves in a polyline with QGIS?

I have a polyline made of curves and I would like to know if there is a way in QGIS to calculate the radius of the curves?
5
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0answers
876 views

Print Composer Template produces empty map?

I have a print composer template which I'm trying to populate with different subset queries from a CSV-derived vector layer using the Python API. However, all the output PDFs contain everything except ...