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Questions tagged [qgis]

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

7
votes
0answers
368 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 ...
6
votes
0answers
129 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
0answers
944 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
votes
0answers
82 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
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 ...
5
votes
0answers
63 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
96 views

Installing QGIS to virtual environment?

I'd like to install QGIS. I'm on a system that defaults to Python 2.5x and I downloaded python 3.7x with homebrew. I created a virtual environment with this code. brew install pyenv brew install ...
5
votes
0answers
57 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
92 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
147 views

Unattended QGIS updates with OSGeo4W

I would like to do an unattended update of my QGIS install every night using windows task scheduler. Is it possible to automatically update all installed packages with the OSGeo4W-Installer without ...
5
votes
0answers
600 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
324 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
189 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 ...
5
votes
0answers
108 views

Render only features located around the the mouse cursor in QGIS?

When hovering over a vector layer in QGIS for feature selection, it would be useful, if only those in a buffer of a certain distance to the mouse cursor are displayed. Any ideas on if/how this might ...
5
votes
0answers
133 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
103 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
0answers
491 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 ...
5
votes
0answers
97 views

Preserving Vector Attribute Types When Processing Vectors

Qgis seems to change vector attribute types for certain processes. Is there a way to force preservation of the attribute types? My situation: I have five vector layers I want to merge, all shapefiles,...
5
votes
0answers
318 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
714 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
413 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
835 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
768 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, ...
5
votes
0answers
858 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 ...
5
votes
0answers
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/...
5
votes
0answers
381 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 ...
5
votes
0answers
650 views

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. ...
4
votes
0answers
31 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 ...
4
votes
0answers
39 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 ...
4
votes
0answers
51 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 ...
4
votes
0answers
47 views

Creating a segment for fixing water pipes and finding disconnected areas

I'm wondering if there is a tool for this problem. I'm using QGIS 2.14.2. Basically I want to select a pipe and find closest valves there is and to turn them off. After that I need to find all pipes ...
4
votes
0answers
256 views

Running OTB Random Forest Classification

I am having trouble processing a satellite image using the RF (Random Forest) classification, that is a machine learning algorithm in the Orfeo Toolbox of QGis 2.18.1. When I run the Tool, the ...
4
votes
0answers
200 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 ...
4
votes
0answers
300 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 "...
4
votes
0answers
73 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 ...
4
votes
0answers
133 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 ...
4
votes
0answers
185 views

How to use a WCS layer in QGIS for processing?

I have a GeoServer serving raster dem data out via WCS and can add the layer easily to QGIS (3.2) but when I try to use it as the input for an operation (e.g. HillShade) I get an error. Processing ...
4
votes
0answers
103 views

Offline editing solution for small GIS project with multiple editors?

I have a specific use-case that I cannot seem to find any solutions for online, so any and all advice would be most welcome. Some basic details: I am part of a small academic organization (a research ...
4
votes
0answers
58 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 ...
4
votes
0answers
84 views

Variable width buffer based on axis directions in QGIS

I need to buffer a polygon with a different distance in the x and y directions. I should add that my polygon has the following properties: closed (obviously) simple (no edge crossing, no more ...
4
votes
0answers
81 views

Single Sided Buffer Error QGIS

I have delineated a shoreline and created an offset "buffer" of 75' and 250'. When projected onto the screen it appears as though a computation error has occurred and the buffers extend onto the left ...
4
votes
0answers
82 views

Adjusting georeferencing of GeoTIFF?

I have three thermal IR images of a boat acquired by a drone as it flew overhead. The images were taken at one second intervals, are GeoTIFF files and overlap one another. I don't know exactly how the ...
4
votes
0answers
55 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 ...
4
votes
0answers
164 views

Investigating PostGIS table not showing in QGIS

I created a table in Postgres: create table eric_zs as select z.id, z.name, st_multi(st_union(a.geom)) as geom, count(*) from geo_as a inner join geo_zs z on a."ZS_id" = z.id group by z.id, z....
4
votes
0answers
79 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 ...
4
votes
0answers
162 views

When does a 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 ...
4
votes
0answers
92 views

Speed execution of PyQGIS algorithms

I don't understand why if I do "manually" some algorithms I get results much faster than when I insert the same in a pyqgis code (with the same input). This happens, for example, with the extract ...
4
votes
0answers
75 views

Halftone effect gridded points inside polygon

I am trying to create smooth looking polygons by gridded points in QGIS (2.18.16), with a fading effect towards the boundary of the polygons (halftone effect). By using the 'fillGrid' function from ...
4
votes
0answers
151 views

QQIS 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 ...
4
votes
0answers
297 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, ...