Questions tagged [qgis]

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

5,925 questions with no upvoted or accepted answers
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2answers
121 views

Calculate the travel time from locations to the closest N points

I want to calculate the travel time (based on walking time) from locations to the closest N points of another dataset. Then I want to create a hull around those N closest points per location Is this ...
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0answers
165 views

“Clip Raster by Mask Layer” produces zero values (and not Nodata) outside mask boundaries

This is my first question here. I have a big raster of the world's nighttime lights and want to clip it down to the Adm0 of a country: In order to do so, in QGIS 2.18 what I do is using the Clipper ...
4
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0answers
35 views

QGIS shared project (monitor changes)

I have a software-development background with a powerful use of svn and git. I work now for a public authority with two offices far from one another. Two other colleagues and I are sharing several ...
4
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0answers
133 views

Slow loading of QGIS project?

I have a number of standard projects set up for QGIS users. Some of them take more than 5 minutes to load. Things recently got much worse suddenly - and I want to track down why. Are there any ...
4
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1answer
69 views

Adding up several rasters to show the change

I want to add several images such that their change is shown in different colors. Such as the following in which I simply added two images in their grayscale. But I would like to have a colored ...
4
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0answers
173 views

Change from LineString to MultiLineString when saving layer edits in QGIS

In QGIS, when a user creates a new single part line in an open editing session for a “Multi-Line” SpatiaLite dataset, the QGIS data type is initially a “LineString”. But, when the user commits the ...
4
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0answers
504 views

Convert TIFF raster layer to PNG

I have been given some images in TIFF format, and I need to convert them to the PNG format. I have been given that the TIFF file contains 4 bands: R, G, B, and NIR (which I do not need for the PNG). ...
4
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0answers
311 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
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1answer
112 views

Selecting or highlighting upstream elements

I would like to use the information from the Swedish SMHI related with their hydrological model elements (catchment areas) that have a Containment hierarchy structure, each element has the information ...
4
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0answers
324 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
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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/...
4
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0answers
293 views

Labelling 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....
4
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0answers
241 views

Local grids with rotated north in QGIS

Like many people in geology and archaeology I need to work with local grids that have eastings and northings from a specific reference point, and typically have a difference alignment/direction of ...
4
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0answers
142 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
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0answers
446 views

Merging two overlapping rasters

There are two rasters A and B. A is smaller but within B and since A has more up-to-date pixel values, I was able to merge A and B with "Mosaic raster layers" tool in QGIS which replaces B pixel ...
4
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0answers
357 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
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0answers
92 views

Different fonts in QGIS2threejs

I'm working with QGIS2threejs for quite a while and it is a great tool! Changing font for the 3D presentation is easy, just change it in the css file. But here is my question: Is it possible to change ...
4
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2answers
380 views

Density map of pedestrian paths and footways in QGIS

I need to identify public places within pedestrian areas in London, so I need to calculate the density of both pedestrian links and footways. I have classified my data according to the categorization ...
4
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0answers
85 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 ...
4
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1answer
170 views

Use DEM elevation attributes in vector polygon?

I am modeling glacier retreat scatching polygons on DEM surface trying to come out with 3D scatch. Is it possible to adjust "height" of polygon to follow elevation of DEM surface (eg. glacier height ...
4
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0answers
255 views

QQIS Automatically Converts UTC Date-Time to Local?

I imported a WFS layer from a geoserver into QGIS and also into a web service that is based on Cesium. The geoserver fetches the data from Elastic search and serves it out as WFS. The date-time ...
4
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0answers
73 views

Creating Raster that sums up input polygons using QGIS?

I am using QGIS and I have a shapefile with buildings. From these buildings, I have built Buffer with variegating radius. The Buffer also have data about the demand for Parking spots for each building....
4
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0answers
247 views

Installing third party python library in QGIS 2.18.x Windows

We are running into a strange behaviour while trying to use pyoidc with QGIS 2.18.x windows standalone version. Due to pip/pipy no longer working with QGIS 2.18 (see this post), we installed the ...
4
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0answers
231 views

Using attributes for output filenames in QGIS Process Modeler?

How can I use process inputs (eg: Table field) inside an expression for an output file when using Process modeler? I have a process which outputs a raster, whose output filename should be the value ...
4
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0answers
514 views

Force layer reload in QGIS?

I'm working on integrating QGIS and PostGIS, but looking for a way to force a layer reload. I don't need it to be automated -- I'm happy to run a command every time I want to refresh the map. The ...
4
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0answers
223 views

Connectors do not appear automatically in easy custom labelling

I'm using the easy custom labelling plugin in QGIS 3. When I move a label away from its associated polygon a connector does not automatically appear as in QGIS 2.18. How do I get connectors to appear ...
4
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0answers
85 views

Bookmarking the rotation, scale, and extent in QGIS

I have one map that I want to bookmark at multiple rotations/orientations. However, when I use the bookmark tool to capture the view, I am only able to capture the scale and extent of each view, and ...
4
votes
1answer
174 views

Sharing properties for SQL server table in QGIS?

I have a project where most of the layers come from a SQL server. Most of the layers contain pointers to, and/or drop down list for, attributes so that there is consistency in data entry. This project ...
4
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0answers
669 views

Add color palette to grey-scale land cover GeoTIFF

I have a single band grey shade tiff image which does not have a a color palette associated with it. I need to open up the symbology and assign a color to each unique landcover class. I am looking ...
4
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0answers
96 views

Speed up identify in QGIS

I have just transferred my Postgis database onto an RDS server, and there is a bit of a performance hit when using the Identify tool in QGIS (3) compared to localhost. I presume this is mostly network ...
4
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0answers
137 views

How to override/edit/fix WMS individual tile requests using QGIS

My question is as follows: I've added a WMS layer into QGIS but when it then goes to display the map and display the tiles, the request is different to what it should be. Is it possible within the ...
4
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0answers
218 views

What bin value does QGis Histogram uses?

I have some single-band rasters (NDVI) on Qgis, for which I can obtain their distribution histogram by going to Right-click > Properties > Histogram Tab > Compute Histogram. This is an ...
4
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0answers
340 views

Avoid duplicate labels on river sections and choose placements

I am trying to label rivers's names. The rivers include multiple sections. I have many repeats like "fleuve Loire ". How to avoid labeling repetition? "Merge connected lines to avoid duplicate ...
4
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0answers
379 views

QGIS Zonal Statistics for polygons is missing results?

I am carrying out an analysis using QGIS 2.14.1 where I am dealing with point data that have been randomly displaced by either up to 2 Km or 5 Km. I have generated a buffer of the appropriate radius ...
4
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0answers
201 views

Creating labels with table style

Hello I'm trying to create a label in QGIS that is formatted similar to the "table" styled yellow labels in the photo below. The attached image was from a map created in AutoCAD. I would like the ...
4
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0answers
74 views

Do the elements in Print Composer have any identifiers in QGIS 2.18.14?

In QGIS 2:18:14, it is possible to refer to elements in the Print Composer? How do I name and identify an element in another element? E.g., on a label, call the contents of another label and use its ...
4
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0answers
226 views

How to set different random colors to adjacent lines in QGIS

I have several line layers which i am trying to style with random colors. I want the lines styled in such a way that adjacent lines are assigned different colors so that each is clearly differentiated....
4
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0answers
248 views

Is it possible to get the compression level of a GeoTiff?

When creating a GeoTiff and using Deflate or LZW as compression it is possible to select the level of compression from 1 to 9. Is it possible afterwards to see which level was used? I have a lot of ...
4
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0answers
686 views

Difference between gdal_calc and QGIS raster calculator

I am hoping someone can help me with an issue I am having with gdal_calc. I am looking to create NDVI rasters from 4 band 8 bit ortho tiles. I have processed the tiles using the following calculation: ...
4
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0answers
682 views

Emerging hotspot analysis (space-time patterns) in QGIS

I worked with crime data a while ago and was really impressed by the possibility in ArcGIS to detect significant hotspots and their development over time (Emerging hotspot analysis). Does anybody ...
4
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0answers
230 views

Orientating Contour Labels Uphill in QGIS?

I'm quite new to QGIS and I'm trying to style topographic contours. I have managed to style the lines the way I'd like but I'm having trouble with the line labels - I can't style them so the labels ...
4
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0answers
277 views

Mapcache zooming problem

I am using mapcache for caching map raster data. Everything works fine except the map zooming, because at the some zoom level i am getting pink tiling images. This is my mapcache xml file: <?xml ...
4
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0answers
163 views

QGIS 2.18.14 vector Clip analysis producing erroneous result

I am trying to perform a vector clip analysis (vector-->geoprocessing tools pull-down menu) using two complicated vector layers and am getting erroneous results. The clip 'Input layer' is shown here: ...
4
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0answers
108 views

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?
4
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0answers
360 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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1answer
266 views

PostGIS table shows twice in QGIS Browser panel

I've observed for a while that for many (but not all) of my tables, QGIS 3 (2.99) shows the same table name twice in the Browser Panel on the left, when I expand my PostGIS data source. The first ...
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0answers
932 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....
4
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0answers
126 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
135 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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0answers
474 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 ...