Questions tagged [qgis]
QGIS is a cross-platform GIS application licensed under the GNU General Public License.
8
votes
0answers
126 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 ...
7
votes
0answers
220 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 ...
7
votes
0answers
361 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
125 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
80 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 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 ...
5
votes
0answers
53 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
53 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
74 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
133 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
591 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
300 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
172 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
103 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
115 views
Calculating Mean and Sum in QGIS Zonal Statistics?
When a polygon intersects more than one pixel, and each pixel within the polygon occupies a different area, does the mean take into account the area of each pixel and its correspondent value (i.e. ...
5
votes
0answers
124 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
503 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
186 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
97 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
454 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
92 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
310 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
704 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
400 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
825 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
746 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
854 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
648 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
37 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
43 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
68 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 ...
4
votes
0answers
217 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
179 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
268 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
57 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
113 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
169 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
96 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
77 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
77 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
80 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
54 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
137 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
72 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
143 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
86 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 ...
