Questions tagged [qgis]

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

6,373 questions with no upvoted or accepted answers
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Automatically creating user CRS from postgis in QGIS

I have my custom CRS in table "spatial_ref_sys" in database. When I load layer from schema "public", QGIS create this CRS. But if layer from other schema, it's not. What I need to solve this problem?
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367 views

Improve washed out blurry composite Landsat 8 image in QGIS

I want to create a composite image using Landsat 8 bands. I followed the steps to do so (creation of virtual layer, high resolution, separate) and adjusted the bands' colors (red 4; green 3; blue 2) ...
4
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984 views

QGIS plugins not installing

I'm trying to install plugins on a fresh install of QGIS 2.18.12. I can connect to the plugins repository but trying to install any plugin fails with the error message: Failed to unzip plugin package....
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134 views

Relation/difference between area calculated by PyQGIS QgsDistanceArea().measurePolygon() and QGIS $area

What is relation/difference between area calculated by QgsDistanceArea().measurePolygon() of PyQGIS and $area from geometry $area in QGIS? I am getting area as 0 for one polygon using QgsDistanceArea(...
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0answers
155 views

Updating PostGIS layer from another vector layer in QGIS?

I have a vector layer that contains way points that I load using "load vector layer" from a gpx file. I am attempting to add these new points to an existing postgis layer by simply copying and ...
4
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509 views

Using csvt file to define column field types - Vector vs Delimited text layers?

I've discovered for myself and also read other post about an issue using csvt file to define the field types - String, Integer, Date, Real ect... The csvt file appears to work as described when ...
4
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113 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,...
4
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125 views

QGIS integer raster stats calculation error

I am comparing two raster temperature files generated from two different sources that use different algorithms. One of them is provided as a floating point (temp(C)) and the other is integer (temp(C)*...
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578 views

Computing the slope of a road using DEM

I work with QGIS 2.14 and I want to create a map of road network showing the slope of each road with at least this scale: <3%; 3-5%; 5-7%; 7-9%; >9%. I already have a vector layer of roads and the ...
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100 views

Sphere rendering inside out using QGIS on Ubuntu?

I'm trying to use QGIS to show earthquakes around a 3d globe. I changed my CRS to 'Sphere_Van_der_Grinten_I' and it rendered like this: Here's a report from Hardinfo on my system and display: ...
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130 views

How much raster data can TimeManager handle?

I have average wind speed data for the UK at 5x5km grids in raster form for every month over 10 years. I load the first 7 months into timemanager and the animation is fluid without any loading/down ...
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4k views

K-Means clustering in QGIS (Attribute based clustering)

In the 2.18.4 and 2.18.5 version of QGIS K-means clustering was moved to a plugin called 'Attribute based clustering'. However, I am working with a virtual raster dataset (vrt.) and the current ...
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267 views

Symbol levels between many layers in QGIS

I have many different layers displaying each a class level from low (blue) to high (red). As I have many layers on different parameters, some low classes can appear on top of high classes, which I don'...
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677 views

Import Pandas or any Python module into QGIS internal Python

(Also asked in stack overflow - https://stackoverflow.com/questions/43244062/import-pandas-or-any-python-module-into-qgis-internal-python ) I am developing a plugin for the current LTR version of ...
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628 views

Clip of polygons does not work properly by invalid geometry

I want to clip a polygon shapefile by another polygon shapefile. Input polygon is the green one (first), clip polygon is the light blue one (second) and the result should look like the dark blue one (...
4
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138 views

Layers from GRASS db won't load in QGIS 2.18.4 desktop

I have been learning QGIS online but now I am stuck at a module. I am supposed to launch a project that includes GRASS vector and point layers. However, when I do so I always receive the 'Handle bad ...
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346 views

QGIS Simple fill symbology for vector layer not exporting to pdf

I'm trying to use simple fill i.e. Diagonal X, on vector layers, the layers look fine on the composer when zoomed out (for example to a scale of 1:6,000) however when I export to pdf the distance ...
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1k views

QGIS: CRS, ellipsoids and area calculation

I have a doubt about dynamic CRS, ellipsoids and area calculations. I am using QGIS 2.14.0 (still waiting for IT to install 2.14.11...) When I load a polygon table into a new, empty project, it comes ...
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77 views

Using euclidian distances as spacing for regular points grid in QGIS?

As a means of checking spatial autocorrelation in the selection of training samples for image classification, I am trying out semivariance analysis. I have managed to generate variograms from image ...
4
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98 views

Avoid adding “_1” to field names when reading csv in QGIS?

When I read my csv file below "Data Source","World Development Indicators", "Last Updated Date","2017-02-01", "Country Name","Country Code","Indicator Name","Indicator Code","1960","1961","1962","...
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699 views

Right-hand-rule in QGIS

It seems that there isn't a plugin to perform the right-hand-rule on a layer or selected features. Can this be done by using some Python code? Is there a function that works in the same way as ...
4
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0answers
143 views

How to change the color ramp of a rule based styling in QGIS?

I use rule-based styling in QGIS, in order to do spatial quantile, computed in R. If I want to change the color ramp, I need to either: change every class color, or set graduated then change the color ...
4
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677 views

QGIS 2.18 + Mac OSX sierra crashes and slow

I've been using QGis for quite a few years on Mac OSX, never had a problem. Now with the current configuration of OSX Sierra + QGIS 2.18.1 many project files that ones were opening nice and smooth ...
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433 views

How to select points with point ids from external list

I have a point shp and list of point IDs in CSV file which match with point IDs in the shape. Points in SHP have location while points in the external file don´t. How can I select points in the shp ...
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230 views

Activating GRASS utilities in QGIS Processing toolbox via text descriptors

This is a new follow-on question from this one. Following the documentation outlined in the answer, it is fairly easy to set up a descriptor text file for standard utilities that exist but aren't in ...
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2k views

QGIS “join attributes by location” fails

I am trying to join attributes from a vector polygon layer to a vector points layer wherever a point falls inside one of the polygons. I tried to use the QGIS 'join attributes by location" tool, ...
4
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0answers
262 views

How to add a Google map layer in a pyqgis script

I'm creating a python plugin for different users that has the layers that each person need to use and work with in QGIS. I have no trouble adding rasters from Geoserver using the following code: ...
4
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325 views

Is it possible to link symbol fill colors between different geometry types in QGIS

I would like to link symbol colors between two layers of different geometry types (point and polygon). I have tried to save/load style and to copy/paste but I don't think its designed to work that way ...
4
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0answers
301 views

Reopening QGIS project from PyQGIS

I am opening a QGIS project using the following snippet: new_project = False if not os.path.exists(self.qgis_project_path): prj_template_path = os.path.join(self.qgis_template_path, 'project.qgs')...
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809 views

QGIS connect to WCS using OAuth2

I'm trying to connect my QGIS to a WCS service using OAuth2 authentication (see curl example below to understand the authentication workflow). the problem The option "add WCS layer" seemed to be the ...
4
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0answers
199 views

How to generate a map showing more than one feature from the coverage layer of Atlas Generator in QGIS?

I have a shapefile (point) with occurrence records of species. There are at least two features for each species, one for currently record and a second for past record. I need to produce one map for ...
4
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0answers
193 views

QGIS attribute table displaying wrong features?

In QGIS 2.18.1 I set up Attribute table to 'Show features Visible On Map' but in the form view in the list are definitely more features than visible in the map. In the screenshot below two features ...
4
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0answers
465 views

PDF looks different from print composer

When I create a map in print composer the map looks exactly how I want it, but when I save it as a PDF some of the sympbols have changed. Note the roads are still visible in the PDF but some have ...
4
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0answers
59 views

QGIS Updating three layers at a time by editing the edge where all the three layers concur

I have a map with three main layers: Roads (Polygons) Sidewalks (Polygons) Curbs (Multilinestrings) I need to adjust the edge where all the three layers concur to the cartography layer (the gray ...
4
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709 views

Open .mdb files in QGIS 2.14.1

I Use QGIS ver 2.14.1 I've got a little problem here I already following how to open mdb at link below : QGIS 2.4 access .mdb add error But error dialog box always pop out when I click "OK" (after ...
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5k views

Is there an “undo” button in QGIS 2.18?

In ArcGIS there an option of "undo" button I seek this option in order to return my steps if it necessary. I try to find such option in the menu and didn't found any like it. What can I do?
4
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345 views

Using Proximity tool in QGIS 2.16

I am using the proximity algorithm to generate a raster proximity map indicating the distance from the coast (points shapefile) of my study area and the center of each planning units (I have divided ...
4
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0answers
411 views

Calculating the maximum remoteness from of the boundary of a polygon (i.e. the radius of the largest circle inscribed in this polygon)

I have two related tasks. How is it possible to solve them (or at the at least the first one, which is the principle task) in ArcGIS or QGIS ? Task 1. How to find a radius of a largest circle ...
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202 views

QGIS removes id field when saving as GeoJSON

I have a GeoJSON file of points which I am editing using QGIS 2.16.1. { "type": "FeatureCollection", "crs": { "type": "name", "properties": { "name": "urn:ogc:def:crs:OGC:1.3:CRS84" } }, "features": ...
4
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0answers
310 views

Making QGIS select correct feature id in PostGIS materialized view?

Can you tell me if there is a way to make QGIS automatically select the correct feature ID when I choose a materialized view in PostGIS? It's not a big deal, but it is nonetheless something I would ...
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74 views

Refining DEM with topographic survey?

I have a DEM that is based on LiDAR and I would like to refine a small area of the DEM with topographic survey points. Is there a good way to do this in QGIS?
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61 views

Is there a way to customize the Options dialog in QGIS 2.14.6?

I'm creating a deployment package to update QGIS from V2.8 (wien) to V2.14 (essen (LTR)). In QGIS 2.14 there is a new "Advanced" section under "Settings > Options", see screenshot: Can this menu ...
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258 views

Saving selected features by default in QGIS?

Is it possible in QGIS (2.14 or higher) to check by default "Save only selected features" when saving a layer and when features are selected ?
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394 views

QGIS 3D Globe Plugin Elevation Map Projection

I'm trying to get a map setup using the QGIS 'Globe Plugin'. I've been trying to use the UK Environment Agency LIDAR data as an elevation map. After a bit of puzzling this out I've found that the ...
4
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0answers
44 views

How to restrict the creation of vectors (end vertices) to existing vertices in QGIS

My specific interest lies in network creation, however, knowing how to do that in general would be a plus. Is it possible to prevent a user from creating a line (line vector) without connecting it ...
4
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0answers
280 views

Can I change the precedence when combining “Control feature rendering order” with QGIS symbol levels?

I'm trying to produce a QGIS map style / symbology for processed openstreetmap data. For roads, I'd like to mimic how the OpenStreetMap web tile map "Standard" rendering style (produced with mapnik ...
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0answers
886 views

Click to copy coordinates From QGIS

I have a created some point data using CRS ESPG:4326 and added Google base map from OpenLayers plugin. While adding the Google Maps imagery I have changed CRS to ESPG:3857 in project properties. ...
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0answers
651 views

QGIS snapping to the points of a line or polygon you are just creating

I have the snapping option enabled. I can snap to any point, intersection of created lines. But I can't snap to any vertex of the linestring I am just digitizing. Is there any option/plugin to ...
4
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0answers
101 views

Style rule based on feature adjacency?

Is there a way in QGIS to use an expression to define a polygon feature's color based on whether it's adjacent to other features? I would like to achieve something like the following: -If a feature ...
4
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0answers
246 views

How to handle large tables in QGIS using python?

I'm currently writing a plugin that calculates values based on a QgsVectorLayer's attributes. To display and print the values I'm using a QgsComposerTextTableV2. I have several problems with my ...