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Questions tagged [qgis]

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

5,679 questions with no upvoted or accepted answers
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81 views

Nested rules in QGIS 2.18

I work with QGIS 2.18. I have a polygon shapefile with two atrributes: id (unique for each polygon) and type. I visualize the shapefile using the "type" attribute, but I would like to add a nested ...
3
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0answers
76 views

Using v.net.flow in QGIS/GRASS GIS?

When I try to use the v.net.flow tool in QGIS, the output datasets have a value of 0 for every feature in the flow column. Almost every other v.net tool works, such as v.net.steiner and v.net.distance....
3
votes
2answers
340 views

Does QGIS 3.6.0 make use of GPUs in order to accomplish 2D tasks (rendering, zooming, panning…)?

does anyone know whether last versions of QGIS (like last one, 3.6.0) make use of GPUs (either integrated or dedicated ones) in order to accomplish 2D tasks (rendering, zooming, panning...)? If it ...
3
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0answers
89 views

Updating shared custom functions / expression code in QGIS

All the QGIS documentation I've seen on custom functions (used in expressions) says that the code is saved in the user's local expressions directory, e.g. ~/.local/share/QGIS/QGIS3/profiles/default/...
3
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0answers
155 views

Difference between units in QGIS: Map Unit vs. Millimeter vs. Inch vs. Pixel vs. Point

In QGIS 2 there were three Unit types: Map Unit, Millimeter and Pixel. With a new version of QGIS 3 two additional arose Inch and Point. What is the difference between those Units, in sense of their ...
3
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0answers
451 views

CadTools plugin functionality in QGIS 3 beyond Advanced Digitising Panel?

I've recently migrated to QGIS 3.6.0, and I've realised that the wonderful CadTools plugin is not compatible with QGIS 3. I tried to use the Advanced Digitising Panel, but it's cumbersome and not ...
3
votes
1answer
69 views

Programmatically styling layer after output is returned from QGIS 3 processing script?

Hi this may be more of a python question rather than qgis processing script question. I've managed to successfully get the output that I want from my processing script, but I wish to take one step ...
3
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0answers
111 views

Create multipoint layer from array by expression

I have two layers. One shapefile point layer, called "point1" and one csv no geometry layer, called "Meta". "point1" looks like: id bd 1 a 2 b 3 c 4 d 5 e 6 f and so on... "...
3
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0answers
48 views

QChainage only works on first part of merged line

I'm trying to merge a number of lines into a single line for chainage purposes. Each individual line is created using OpenRouteService, then merged into a longer continuous shape using Edit > Merge ...
3
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0answers
207 views

Automatically update and reclassify project layer from Excel data

I have a project in Qgis that gets its data from a locally stored excel file (linked). Is there a way to automatically update the linked data? What is happening now is that when I change some rows in ...
3
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0answers
59 views

Clustering based on eqaul populations

I have a map of a city that is divided into 65 sectors (building lots in purple, sector boundaries in red): In my shapefile of building lots, I have an attribute that is the total population within ...
3
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0answers
115 views

Spell check tool for layouts in QGIS?

Perhaps I'm missing something obvious - but is there no built-in spell check tool in QGIS? I know spell checking attribute data may be a waste of time; but I would expect a tool for layouts, just to ...
3
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0answers
94 views

Line perpendicular to the maximum axis of an irregular polygon (sinkholes) QGIS 3

I am performing a morphometric analysis of dolines using QGIS 3. The analysis consists of determining the longest axis (the union of the two most distant points of the polygon) and the shortest axis ...
3
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0answers
69 views

QGIS Server Adding a virtual layer

All my layers in the qgs-project-file are working fine as WMS-layers, but I only can't provide the virtual layer. The virtual layer is an ODBC-Connection of an Access-Database which contains one ...
3
votes
0answers
199 views

How to create LineString geometry in QGIS3?

The default geometry type for a newly created line seems to be MultiLineString. It can be changed to LineString using the Multi to Single tool while saving in memory. However, once it is exported it ...
3
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0answers
156 views

QGisPlugin : Trigger closeEvent by clicking 'X' in QgsAttributeForm

This is the code: def formOpen(dialog, layer, feature): """Function called when a connec is identified in the map""" global feature_dialog # Create class to manage Feature Form interaction ...
3
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0answers
168 views

Loading editable SQLite layer in QGIS?

I converted a shapefile to a SpatiaLite database so I could work with attributes with a length longer than 254 characters, and also not see some columns and change their order. In QGIS 2.18.16 I have ...
3
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0answers
83 views

QGIS Auto-update function/script

With the help of @Kazuhito, I have achieved a fine result in my valve and pipe simulation project. When I close a random valve, all flow in this direction is automatically closed and the color changes ...
3
votes
0answers
230 views

Writing masked GeoTIFF in rasterio and visualizing in QGIS?

I have an interpolated raster, which is a masked array, that shows where the data is valid. I want to save it as masked TIFF with rasterio. To test, here's the JSON file, and the code: import ...
3
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0answers
216 views

How to print automatically Map themes in Label's Map Composer?

This expression [%@project_path%] prints the path of the qgis project. How the Map Theme used in the layout can also be printed automatically ? According to QGIS documentation, a Map Theme is a ...
3
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0answers
75 views

Changing legend spacing to be further away from map border in QGIS?

I am using QGIS 3.2.3 I am creating a map in which I have added a legend to (see figure below). My issue is that I am trying to create a legend which has spacing between the two columns. I have ...
3
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0answers
61 views

QGIS - Sorting of features in referenced child layer

I'm using QGIS 2.18 and 3.2. I have a point layer (PostGIS) and another layer without geometry. The layers are connected with 1 to many relationship, the parent being the layer with the geometry. ...
3
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0answers
143 views

Finding correct CRS using QGIS?

I have a GeoTIFF layer (downloaded from US Dept of Interior) that is US population density. The metadata claims it is in EPSG:4267, which isn't even intended for use in that part of the world. (east ...
3
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0answers
351 views

QGIS 3.4.2 not loading .tif files correctly

I have a surface which has been exported from Civil3D and added to both QGIS 2.18 and 3.4.2 When added they both look very different and the imported image and values in 3.4.2 is not very helpful in ...
3
votes
0answers
153 views

Memory errors when doing Zonal Statistics on a multi polygon shapefile in Python

I want to calculate the mean NDVI with the EthNdvi.tif file for each zone (there are around 650 admin zones) in the the woreda shapefile. I'm having some issues with running the following lines of ...
3
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0answers
158 views

How do I fill Landsat 7 SLC gaps using QGIS?

I am currently using the QGIS 3.4.0 Raster -> Analysis -> Fill nodata (a tool for Landsat 7 data). I am using the directly downloaded USGS tiff band files with corresponding gap mask band tiffs ...
3
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0answers
29 views

We need to have a login occur before QGIS3 loads

Where is the hook for the invocation of the QGIS3 launch? I have looked at the pyqgis api and did not find a bootstrap class or anything similar.
3
votes
0answers
122 views

Georeferencing image in QGIS?

I have a problem with projection. When I try to georeference an image in QGIS, I set up CRS WGS 84 Pseudo Mercator (EPSG: 3857). That info appears in georeference settings and it is also my default ...
3
votes
0answers
197 views

Problem with insert into PostGIS view table via QGIS

I use a PostgreSQL 9.5.14 (PostGIS) and QGIS 2.18.7. The problem is that when I try to add a new object to the View via a QGIS, the following error occurs: ERROR: column "geom" is of type ...
3
votes
0answers
113 views

QGIS 3 - Save processing output to memory and turn into numpy array?

I'm currently developing a python plugin for QGIS 3. In short, the code conducts among others a viewshed algorithm, turns the output in a numpy array and calculates some spatial metrics the user can ...
3
votes
0answers
143 views

Could not allocate required memory for image

I'm trying to export a 24k image (export set to 1650DPI) using the "export as image" function but I keep getting the "Could not allocate required memory for image" warning. I don't understand why ...
3
votes
0answers
177 views

Collada file mirrored when created with qgis2threejs in QGIS 2.18

When I export a Collada file from QGIS 2.18.23 using the amazing QGIS2threejs plugin version 1.4.2, my Collada file comes into Blender and Sketchup with the East West mirrored. This is not the case in ...
3
votes
1answer
194 views

File naming iteration QGIS modeler

I am attempting my first use of the modeler from the Graphical Modeler from the Processing menu in QGIS. I made a simple model for cliping species data by sanctuary.It has two Vector Inputs, uses some ...
3
votes
0answers
100 views

QGIS Python: sort by attributes <= 0

In QGIS 2.18 I'm try to sort features by an integer attribute with a Python script. The problem is, that some of the values of the sorting attribue are <= 0 (for sure they have to be <=0) and ...
3
votes
0answers
40 views

Nesting styles for increased drawing speed

I have zoning plans for a municipalities ( for example 5700 features in this one) and I have created a QGIS-style to make it look like the offical style. There are 72 colours/patterns for the ...
3
votes
1answer
411 views

startup.py in QGIS not executed

I would like to use a startup.py which is part of a rollout and not located inside the users config-folder (like ~/.qgis2). Plugins located in the apps folder (e.g. C:\OSGeo4W64\apps\qgis-ltr\python) ...
3
votes
0answers
183 views

How to export “solid” 3D objects from QGIS to DXF?

I work in architecture and we often have to create urban contexts for our projects which involves obtaining a building footprint file and then extruding them by hand. I have attempted to use QGIS (v3....
3
votes
0answers
58 views

How can I get real time log in .bat file at QGIS & PlugIn with Python PyQT4

I try to get real time log in batch file with python, then show it to QGIS Plugin real time. ( .bat file have run -jar file ) I success logging but not real time log in QGIS because QGIS is stopped ...
3
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0answers
1k views

Add an API key to QGIS

I still can't seem to get this (Add an API key to QGIS for QOSM layer) to work. I need to add an API key to QGIS for OpenCycleMap. I'm trying to follow the path Web > OpenLayer plugin > OSM/...
3
votes
0answers
422 views

Why is the attached WMS service not working with QGIS and QGIS2WEB?

I am using QGIS2WEB (open layers) to develop a small platform with geodata. I am having trouble integrating the following WMS service into my webmap: http://geoportal.frankfurt.de/opendata/...
3
votes
0answers
247 views

How to label a rubber band (QgsRubberBand)

It is possible to label QgsRubberBand or QgsVertexMarker with a text annotation (QgsTextAnnotationItem). See this MWE: ... r_polyline = QgsRubberBand(iface.mapCanvas(), False) r_polyline....
3
votes
0answers
191 views

Create lines to connect vertices in QGIS

I have a file that marks street edges and want to connect "crossing" points automatically. Image 1 shows the street edge, Image 2 shows the desired result. Is there a plugin or method I can use to ...
3
votes
0answers
79 views

QGIS - Parallel Lines - Count length of one

I have a large layer of lines (telecommunication duct) with in parts several parallel lines that are close to each other (cause they lay in the same trench). I would like to count the length of the ...
3
votes
0answers
135 views

Recognizing when road is uphill and when downhill using QGIS?

How do I automatically recognize and cut roads of a great network in places when the roads are changing the path uphill and downhill using QGIS? I have a geotiff dem. Schematic truck's transport
3
votes
0answers
102 views

QGIS: QgsMapCanvas rotate vs setRotation

Question regarding QgsMapCanvas using python for QGIS : what is the difference between the following two methods? myQgsMapCanvas.rotate(10.0) myQgsMapCanvas.setRotation(10.0) (myQgsMapCanvas ...
3
votes
0answers
251 views

QGIS draw line segments with “geometry generator” based on segments angle

I have quite a hard problem to solve here and I don't know if its even possible with the geometry functions in QGIS. I have a line geometry with equidistant vertices, that is, same length segments. ...
3
votes
0answers
128 views

Identification of roof peaks on a Raster in Qgis

I am trying to map all the flat roofs of a city. After processing my data I have a huge raster with the zones that are flat (=1) and not flat (=0). I can overlap the roof polygons over this raster and ...
3
votes
0answers
74 views

Setting output filenames from QGIS modeler?

I have built model which iterate through features in input layer. How I can set output filenames in the modeler using input rows? Something like current_field_value.shp
3
votes
0answers
113 views

Drawing a line to a point - style in QGIS

I need to create a style in QGIS in which the line is moved away from the second line by 2 units, but their ends merge at one point. I created 3 geometry generators - 3 lines. At the ends of the line: ...
3
votes
1answer
366 views

Backup QGIS (3.2.1) layer to independent PostGIS table?

I'd like to make multiple, progressive backup copies of QGIS (3.2.1) layers that are stored in PostGIS tables. I've tried multiple routes to export them as files on disk, but they all seem to destroy ...