Questions tagged [qgis]
QGIS is a cross-platform GIS application licensed under the GNU General Public License.
5,512
questions with no upvoted or accepted answers
10
votes
0answers
422 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 ...
9
votes
0answers
177 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
696 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 ...
7
votes
0answers
835 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
votes
0answers
149 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
votes
0answers
87 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 (...
6
votes
0answers
137 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
675 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
266 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
186 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
votes
0answers
159 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
442 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
0answers
430 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
216 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
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 ...
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
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
0answers
87 views
Selecting line features by topology in QGIS (select dangles)
I want to select line features by their relationship to their neighbouring line features.
To perform generalisation on the data set I need to select lines that:
Do not intersect with their end point ...
5
votes
1answer
152 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
163 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
52 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
122 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
67 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
148 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
305 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
337 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
208 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
68 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
361 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
633 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
414 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
159 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
132 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
363 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
403 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
116 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
137 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
289 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
351 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
739 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
439 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
442 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
892 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
315 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
2answers
4k views
WindowsError: [Error 32] The process cannot access the file because it is being used by another process
I am reading images (through Python) and do something. These images are placed in a temporary file, through:
tf = tempfile.mkdtemp(filename)
I use gdal to read the images (short part of code):
...
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