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Questions tagged [qgis]

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

14
votes
0answers
353 views

Determining flow path length in QGIS?

I need help with qgis flow path length. I try to run the program and when I run the program I get a raster with 0 values, as input I'm using filled raster, I don't now if I'm doing something wrong or ...
11
votes
0answers
217 views

Showing startup-messages on QGIS splashscreen

During the startup of QGIS there are status messages shown in the lower part of the splashscreen like "restoring loaded plugins". I am using a startup.py from which I would like to inform the user ...
9
votes
0answers
135 views

Options for generating travel time isochrones in QGIS 3.4: what do you use?

I'm currently using the updated OSM tools to generate isochrones in QGIS 3.4, which works well (example below). My question is just what methods other people use and whether there is something better ...
8
votes
0answers
242 views

QGIS 3 and SAGA 3.0+ Integration

I've looked all over the net and I'm wondering if there are any plans by the QGIS developers to integrate some of the newer versions of SAGA available in the repository and as binaries on the project'...
8
votes
0answers
249 views

Calculating new field works inside QGIS Python console but not in standalone program

My code in the standalone program import sys sys.path.append("C:/OSGeo4W64/apps/qgis-ltr/python/plugins") from qgis.core import * from PyQt4.QtCore import * from PyQt4.QtGui import * import ...
8
votes
0answers
156 views

Remove “Save As” from QGIS Context Menu Using PyQGIS

I want to remove an Existing Option ("Save As") from context menu of QGIS layer, what I have found so far is, to add new action in the LegendItems, or overwrite completely with new options. But could ...
7
votes
0answers
156 views

Multithreaded DB connection for QGIS plugin

I am using QGIS 2.18.21 and PostgreSQL 9.6. on a Windows 8 machine. I am trying to do processing of a certain database task in the background, and I want the user to be able to continue to work in ...
7
votes
0answers
148 views

Buffered one-to-many spatial join QGIS3

I'm trying to spatial join bus stops and census block groups. However, these are a bit tricky with walking distance. Many bus stops are right on the borders of census block groups or within walking ...
7
votes
0answers
91 views

Open WMTS query parameter encoding with “+” character in QGis

I am trying to create a WMTS endpoint with query parameters in the urls that contain a + character. So my resource url looks like this: <ResourceURL format="image/png" template="http://localhost/...
7
votes
0answers
187 views

Is it possible to open MapGIS files ( .WL, .WP & .WT ) in QGIS or other GIS?

We received some files from clients located in China created in a program called MapGIS. I was wondering if anybody knows how to make QGIS or any other GIS program, excluding MapGIS, open these files? ...
7
votes
0answers
1k views

How to force geometry type in mixed geometry WFS layer in QGIS?

I have an external WFS source serving mixed geometry types - in other words, I have no control of the source. When adding the layer QGIS sets the geometry type to line and thus I am unable to style ...
6
votes
0answers
72 views

Stopping never ending QGIS processes instead of forcing QGIS to quit?

being a new to using QGIS on an iMac I often start processes on a large data-set that sets the spinning wheel in to a never ending state. I often need to force quit the whole QGIS program to break ...
6
votes
0answers
492 views

Gdal and module import error when creating an .exe application with pyinstaller

I’ve been struggling since three days in a row to create a windows executable application from my python application. I have managed to get results but I’m not at all satisfied with the workarounds I ...
6
votes
0answers
435 views

QGIS 2.8 Python Plugin Unittest Segmentation Fault 11

UPDATE: This issue may be isolated to my MacBook. The seg fault did not occur in testing on Windows. I have put together a sample unit test for a QGIS python plugin. It is causing a Segmentation ...
6
votes
0answers
2k views

Rasterize shapefile using another raster's size and resultion

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
353 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 ...
5
votes
0answers
104 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
101 views

QGIS versions yielding different results on $area calculations?

When grading an exam, I discovered that QGIS 3.2 and 3.4 produce different values on computing $area over polygons. I experimented using $area and area($geometry) to check the differences between ...
5
votes
0answers
30 views

Can QGIS 3.0 identify tool give labels as well as band values for selected raster pixels

I'm using QGIS 3.0 for comparison of several landcover grids. These have a set style with 72 categories of landuse. The Style menu allows you to give a text label for each value within a band. The ...
5
votes
0answers
207 views

Execute SQL in QGIS Graphical Modeler

I'm trying to sort a shapefile by one of its attributes using "Execute SQL", in the QGIS Graphical Modeler. Using a vector as input is working fine, but when I use a layer generated by an algorithm ...
5
votes
0answers
559 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
241 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
152 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
87 views

Possible to render only those 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
115 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
443 views

QGIS select by location failing

I'm performing a simple select by location. I want to select polygons from TQ_Building that fall within rapidair_AOI, a larger polygon. My workspace looks like this: I'm using QGIS 2.18.13. I've ...
5
votes
0answers
168 views

Packing squares polygons in a raster grid

In the green area of the raster I have to fit as many square polygons as possible, of three different sizes: 3x3 cell size 2x2 cell size 1x1 cell size With the fact that the approach should be ...
5
votes
0answers
87 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
87 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
260 views

Clean up QGIS project file *.qgs

I'm using a QGIS project as template for other projects. This template has got around 5000 rows. Because I do several updates to the file, it's getting larger and more complex by the time. I know, ...
5
votes
0answers
278 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
77 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 ...
5
votes
0answers
678 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
384 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
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
794 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
204 views

OS terrain 50: .vrt from zip files

I tried to follow what was suggested in How to use OS Terrain 50 in QGIS, but I got the following problem: in spite of being generally able to generate .vrt files using gdalbuildvrt from unzipped ....
5
votes
0answers
258 views

How to change the group icon in legend via Python in QGIS 2.6?

How to change the group icon in legend via Python in QGIS 2.6? At version 1.x I did it this way: self.legendTree = self.iface.mainWindow().findChild(QDockWidget,"Legend").findChild(QTreeWidget) ...
5
votes
0answers
702 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
845 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
307 views

Adding field to table using QGIS graphic modeler?

I was wondering if anyone could help as I'm struggling to get anything out of the QGIS graphic modeler. I need to be able to add a new field to an attribute table and update that field with a value ...
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
754 views

How to load the default layer style from Postgresql with Python?

I would like to write a python macro that upon opening my QGIS project file will reload the default style for each layer from the postgres 'layer_style' table. I have had a look at the documentation ...
5
votes
0answers
641 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
175 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
41 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
84 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
122 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
66 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
413 views

QGIS 3.2 Auxiliary Storage feature. Can it be bypassed or deactivated?

Up until QGIS 2.18, all our text placement and rotation values were set to point to the spatial layer table in MSSQL, where we added an ANG (angle) and X, Y field for rotation and placement value ...