Questions tagged [qgis]
QGIS is a cross-platform GIS application licensed under the GNU General Public License.
5,845
questions
7
votes
1
answer
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Use QGIS expressions to create geometries: difference between geometry generator and geometry by expression
QGIS has a powerful expression machine that can be used (between other things) to create new geometries, based on existing layers. Basically, there are two options: Geometry generator and Geometry by ...
- 40.1k
180
votes
7
answers
210k
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Installing File Geodatabase (*.gdb) support in QGIS
I have spent around 2 days to find the way to open GDB (ESRI Geodatabase) in QGIS (or any other open source software) but still without success.
I have downloaded the newest OSGeo4W installer and ...
- 9,216
49
votes
7
answers
46k
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OpenLayers low resolution and/or shifts in QGIS print composer?
I'm having trouble with the OpenLayers Plugin of Qgis and the map composer:
If I create an OSM-background layer and if I want to export this, the OSM-Layer looks perfectly all right in the normal ...
- 2,161
196
votes
6
answers
486k
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Adding Basemaps from Google or Bing in QGIS
ArcGIS Desktop has the option of using basemaps from ArcGIS Online.
Does QGIS have any such options?
- 3,191
51
votes
3
answers
65k
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Reprojecting vector layer in QGIS
I have a series of layers of lines (shapefiles) in My Project. The CRS of some are different and to merge them they all must have same CRS.
When I use Processing > Toolbox > Qgis_algorithims >...
- 511
9
votes
1
answer
1k
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Changing shapefiles from geographic (WGS84) to projected (EPSG:2263) coordinate system using QGIS
I am trying to calculate service area polygons using the QNEAT3 plug in tool for a project I am doing. However, I got an error before these polygons could be created.
2021-01-04T08:03:38 CRITICAL ...
- 173
108
votes
8
answers
261k
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Calculating polygon areas in shapefile using QGIS
How do I calculate areas of an area shapefile in square meters (m²) or in acres (ha)?
I didn't find that functionality in the Vector Tools.
- 2,161
25
votes
2
answers
14k
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Displaying world country shapefiles centered on Pacific Ocean using Robinson or Miller Cylindrical projection in QGIS?
I wish to display a map in QGIS (world country shapefiles) showing all countries but centered on the Pacific area.
I am not familiar with Proj4, so is there any way this can be done in QGIS?
- 271
35
votes
7
answers
45k
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Fixing geometry validity errors in QGIS 2
I am working on ownership data at a US county level. I have one shapefile per county that contains thousands of tax parcels. I need to dissolve the polygons representing parcels owned by the same ...
- 915
36
votes
8
answers
44k
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Georeferencing vector layer with control points using QGIS?
I have a non-georeferenced vector layer that I need to be georeferenced. With raster layers the task is easy and straightforward, but I have no idea what should I do with my vector layer. I have a few ...
- 461
54
votes
7
answers
135k
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Getting list of coordinates for points in layer using QGIS?
I've got a layer in QGIS that is comprised of points. Its attribute table doesn't have (show) the corresponding x and y coordinates for each point. Is there a way for me to extract a list of ...
- 2,977
29
votes
2
answers
20k
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Understanding Join Attributes by Location in QGIS?
I wonder if there is somewhere an explanation for the parameters that can be set when running the Algorithm "Join Attributes by Location" in QGIS 2.18.
I had a look here:
Documentation QGIS Testing |...
- 3,017
32
votes
7
answers
39k
views
Joining multiple records to single feature using QGIS
I'm trying to create a join/relate in QGIS where I have a shapefile of buildings and to that I would like to join a non-spatial table (.csv-file) containing people who work in each building. So I have ...
- 321
34
votes
7
answers
58k
views
Changing CSV layer attribute value from text to number in QGIS?
I read in a CSV file for linking to a .shp file.
All the variables that are just numbers came in as text.
How do I change the text variables to numeric in QGIS?
- 957
22
votes
5
answers
19k
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Finding centrelines from polygons in QGIS
I was wondering if there is a way to create center lines from polygons in QGIS?
I have a polygon layer, but ideally need the centerlines as a separate file.
- 2,397
38
votes
7
answers
54k
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Performing Raster Reclassification in QGIS
Is there a way to perform a reclassify of a raster image in QGIS?
In ArcGIS Desktop you can do that in Spatial analyst Tools→Reclass→Reclassify
- 3,326
57
votes
11
answers
63k
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Removing small spaces (slivers) between polygons?
I have a set of polygons representing administrative districts. The districts were digitized by hand, and there are small spaces (slivers) between polygons where the polygons should be touching.
How ...
- 681
67
votes
5
answers
114k
views
Clipping raster with vector boundaries using QGIS
In QGIS I would like to clip a raster precipitation layer using an admin boundary layer that is vector data. However the Geoprocessing tools seem to be usable only for vector data.
How can I clip this ...
- 671
42
votes
5
answers
79k
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Splitting shapefile into separate files for each feature using QGIS or SAGA [closed]
I have a polyline shapefile with about 20 kinds of roads.
I would like to know how can I create automatically a vector file for each one.
I am aware of how to do it using ArcGIS Desktop - see ...
- 429
25
votes
1
answer
29k
views
Understanding QGIS buffer tool units
I have had no luck getting the buffer tool to accept anything but degrees as units of measure.
I have found lots of stuff saying the layer needs to be reprojected and saved but it hasn't worked at ...
- 353
7
votes
1
answer
3k
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Layer is not valid error in my standalone PyQGIS script/app
I have written a python class which reads properties of map layers from an XML file and creates appropriate memory layers. I have developed and tested this code with QGIS 2.8.2 on a Windows 7 machine (...
- 4,400
53
votes
13
answers
19k
views
Seeking QGIS user interface tutorials and web resources
I wish to familiarize myself with the capabilities of QGIS up to and beyond QGIS version 3.0.
Can you recommend some good web resources and tutorials that would show me QGIS' capabilities?
I am ...
106
votes
5
answers
245k
views
Merging multiple vector layers to one layer using QGIS
I've imported several shapefiles which where exported from a Mapinfo .tab. Several .tab-files are imported resulting in 20+ layers.
Afterwards I want to export it to GeoJSON; but I'm reluctant to ...
- 2,109
40
votes
1
answer
24k
views
Defining new custom projections in QGIS?
I'm trying to define a projection in QGIS. I want to add North America Albers Equal Area Conic. From the spatialreference site I copied the proj4 line:
+proj=aea +lat_1=20 +lat_2=60 +lat_0=40 +lon_0=-...
- 15.9k
22
votes
3
answers
34k
views
Adding Direction and Distance into attribute table in QGIS
I just want to add direction (Bearing: i.e N 25 35 E) and Distance (Length: 125 meters) as my new field in polyline/line data.
Is there a Plugin to generate these fields?
I tried to used Export/Add ...
- 306
16
votes
1
answer
31k
views
Using Elseif Conditional Statement in QGIS Field Calculator?
I am trying to write an ELSEIF conditional statement in QGIS Field Calculator (version 1.8.0). I have used an example I found online:
CASE WHEN val < 0 THEN 'negative'
WHEN val = 0 THEN "neutral'...
- 9,203
38
votes
4
answers
59k
views
Creating DEM from contours in QGIS?
I have a shapefile with contours and their heights.
Is it possible to make a DEM from contours in QGIS without using GRASS?
I found Creating DEM from contours using ArcGIS Desktop? but the answer ...
- 3,326
21
votes
3
answers
74k
views
Creating buffer in meters
Objective
Given a list of coordinates in longitude/latitude, stored as a .csv file, I want to create a buffer with distance of x km around those coordinates. (In case this is relevant, these ...
- 313
7
votes
1
answer
516
views
Understanding Coordinate Reference System of QGIS Project and Layer
I do not understand why there can be in QGIS different CRS for project and for layers. I have worked previously with subsurface petroleum software and there CRS "stuff" was lot more strict ...
- 493
31
votes
2
answers
17k
views
Filtering features in other layers of QGIS Atlas
I'm trying to use the QGIS Atlas tools to build student 'scattermaps', i.e. display the school and the students that attend that school, for 215 schools.
The schools layer is the coverage layer, and ...
32
votes
9
answers
68k
views
Calculating latitude and longitude of points using QGIS
How do I easily calculate the lat/long of points using the QGIS Field Calculator?
I saw a previous related question (Using QGIS API and Python, to return latitude and longitude of point?), but it ...
- 15.9k
13
votes
2
answers
49k
views
How to calculate polygon areas and perimeters using QGIS?
Using QGIS, if I load a polygon layer and make a new column, how do I fill that column with the:
area of each polygon and another column with
length of the perimeter of each polygon?
- 957
46
votes
1
answer
63k
views
Installing QGIS plugin when offline
Due to various IT policies at my workplace, QGIS is installed on a machine that is not connected to the Internet. I wish to install a couple of QGIS plugins on this system.
I have downloaded the ...
- 39.8k
20
votes
5
answers
29k
views
Nearest distance between point and line layers in QGIS
I have two layers, a line and a point layer.
I need to make a line layer which connects all the points to the nearest line feature. How can I do that?
Is there a plugin available for QGIS?
This is a ...
- 2,197
24
votes
4
answers
112k
views
Changing projection of shapefile in QGIS
How do I change the projection of my shapefile using QGIS?
The default projection is set to EPSG:3003, I want to change it to WGS84 EPSG:32632. When I do a reprojection or I change projection in the ...
- 491
12
votes
3
answers
17k
views
Installing ECW for QGIS in Ubuntu 12.04?
I have followed various online help guides on how to make ecw for QGIS 1.8 work in Ubuntu 12.04. I had it all working in Ubuntu 10.04 but since migration to 12.04 no such luck.
Is there a guide that ...
- 129
54
votes
9
answers
74k
views
Missing Processing Tools in Vector Menu of QGIS
I'm missing all the usual processing tools in the Vector menu in QGIS 2.16 (e.g. Vector Overlay, Analysis, etc). They do appear in the processing toolbox but there's no sign of them in the Vector menu....
- 876
5
votes
5
answers
8k
views
Unable to install ECW support on lubuntu 14.04
I try unsuccessfully to install the ECW support (mainly to use ECW file in QGIS 2.2).
We attempt to follow and adapt the howto provided by makina-corpus.
My first supprise was the repository ...
- 53
30
votes
5
answers
46k
views
Creating fishnet grid Shapefile in QGIS?
How do I create a fishnet shapefile using QGIS?
The equivalent task of "Create Fishnet" in ArcGIS.
- 3,485
10
votes
4
answers
7k
views
Dissolving polygons in QGIS or GRASS to new polygons of defined population sizes
I have a shapefile with 3800 polygons representing the smallest administrative areas in Ireland. Many of these, in rural areas, have tiny populations, under 100 people. In urban areas, all would have ...
- 249
38
votes
5
answers
27k
views
Joining attributes from nearest point in QGIS?
I have two layers with points, call them A and B, each with different attributes.
For each point in A I want to join all the attributes from the nearest point in B.
Ideally this would also include ...
- 664
39
votes
9
answers
55k
views
How to set all pixels with value <= 0 to "nodata" in DEM raster?
I have a DEM raster with pixel values between about 3000 and -0.0003.
I need to set all pixel with a value of 0 and smaler (<=0) to "nodata" (for later raster calculations and to reduce the ...
- 7,663
56
votes
2
answers
116k
views
Selecting features within polygon from another layer using QGIS
I'm using QGIS 1.8 with a PostGIS database and I have three PostGIS layers in QGISL: a lines, a points, and a polygon.
I'm trying to select features in the polygon layer and mark all points within ...
- 561
40
votes
4
answers
63k
views
Loading OpenStreetMap data in QGIS?
In QGIS 1.8 I used the openstreetmap plugin to request data from the server, or open a .osm XML file, which produced 3 layers (polygons, polylines and points) in QGIS.
This was great (give or take ...
- 523
19
votes
6
answers
36k
views
Filling holes in polygons automatically using QGIS
Is there an option in QGIS to fill holes in polygons automatically by setting parameters e.g. maximum area, distance between borderlines?
I want to delete/fill holes that a very "thin"/small....
- 199
16
votes
3
answers
19k
views
Splitting all lines in layer at vertices using QGIS
I want to automatically split all lines in a QGIS layer at their vertices (like this).
I've done a Google search and found this article, which is quite close but the workflow is complicated. Because I'...
- 1,846
8
votes
2
answers
6k
views
Calculating proportional area of polygon within another layer's polygon using QGIS
I have two polygon layers, 'model' and 'ntem', whose features overlap and intersect one another.
I would like to calculate the proportion of the area of the 'model' polygons which fit within each '...
- 477
6
votes
2
answers
7k
views
Getting incorrect slope values from an ASTER DEM in QGIS?
I have a DEM layer from ASTER satellite and I want to get the slope information from it.
I use terrain analysis > slope, but the output is so wrong. Why is that?
Here is the DEM:
And here is the "...
- 665
23
votes
3
answers
15k
views
Accessing raster attribute table in QGIS?
I have some Python code that makes Raster Attribute Tables for GeoTiffs using GDAL.
In ArcGIS I can see these attribute tables fine and they behave how I like (as classifications) but in QGIS the ...
- 1,520
15
votes
2
answers
21k
views
Completely uninstalling and removing QGIS 2.8.1 on Windows Vista
I want to uninstall and completely remove QGIS installation from my computer (Windows Vista). I have uninstalled it and when i try to reinstall it says it is already installed on the system.
- 1,153