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Questions tagged [qgis]

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

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13 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 (introduced in ...
Babel's user avatar
  • 71.3k
12 votes
1 answer
6k views

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 ...
UnionTpke's user avatar
  • 203
184 votes
7 answers
234k views

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 ...
Miro's user avatar
  • 9,744
49 votes
7 answers
48k views

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 ...
desputin's user avatar
  • 2,311
7 votes
1 answer
2k 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 ...
Marin Mirošević's user avatar
122 votes
8 answers
344k views

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.
desputin's user avatar
  • 2,311
212 votes
6 answers
566k views

Adding basemaps in QGIS

ArcGIS Desktop has the option of using basemaps from ArcGIS Online. Does QGIS have any such options?
SNT's user avatar
  • 3,379
53 votes
3 answers
73k views

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 >...
razi's user avatar
  • 531
27 votes
3 answers
16k views

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?
user21658's user avatar
  • 291
40 votes
10 answers
52k views

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 ...
AHaav's user avatar
  • 501
37 votes
7 answers
46k views

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 ...
Bap's user avatar
  • 983
32 votes
3 answers
32k views

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 |...
four-eyes's user avatar
  • 3,378
27 votes
6 answers
25k views

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.
Alan Carr's user avatar
  • 2,475
9 votes
1 answer
4k views

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 (...
Detlev's user avatar
  • 4,608
58 votes
7 answers
166k views

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 ...
hpy's user avatar
  • 3,157
32 votes
7 answers
43k 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 ...
Mick's user avatar
  • 321
47 votes
5 answers
94k views

Splitting shapefile into separate files for each feature using QGIS or SAGA

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 ...
Bobo's user avatar
  • 479
36 votes
7 answers
62k 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?
HealthMaps's user avatar
68 votes
5 answers
134k 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 ...
Kirk's user avatar
  • 681
39 votes
7 answers
63k views

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
Vassilis's user avatar
  • 3,444
25 votes
1 answer
30k 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 ...
haxwithaxe's user avatar
112 votes
5 answers
286k 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 ...
stUrb's user avatar
  • 2,279
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 ...
41 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=-...
djq's user avatar
  • 16.3k
33 votes
2 answers
24k 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 ...
DPSSpatial_BoycottingGISSE's user avatar
5 votes
1 answer
1k views

Fill attribute-table on feature-creation based on intersection with other layer

I am digitising line-features based on WGS-84 point-coordinates from a PDF which cannot be copied from. The final line layer should contain lines which each connect two points and have the following ...
Erik's user avatar
  • 16.3k
38 votes
9 answers
93k 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 ...
djq's user avatar
  • 16.3k
24 votes
4 answers
97k 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 ...
Herr K.'s user avatar
  • 343
22 votes
3 answers
39k 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 ...
arzandia's user avatar
  • 306
17 votes
1 answer
33k 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'...
Ryan Garnett's user avatar
  • 9,479
24 votes
4 answers
126k 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 ...
Filippo's user avatar
  • 503
14 votes
2 answers
56k views

Calculating 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 the length of the perimeter of each polygon?
HealthMaps's user avatar
40 votes
4 answers
69k 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 ...
Vassilis's user avatar
  • 3,444
40 votes
8 answers
71k views

Setting all pixels with value <= 0 to "nodata" in DEM raster using QGIS

I am using QGIS. 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 ...
MartinMap's user avatar
  • 8,262
27 votes
5 answers
42k 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 ...
Frodo's user avatar
  • 2,407
57 votes
10 answers
93k 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....
user77875's user avatar
  • 906
50 votes
5 answers
94k views

Smoothing/generalizing polygon in QGIS

Is it possible to smooth or generalize a polygon in QGIS, perhaps by using a plugin like the Generalizer Plugin for lines? I could convert my polygons to lines, smooth them and convert them back to ...
MartinMap's user avatar
  • 8,262
46 votes
1 answer
65k 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 ...
Devdatta Tengshe's user avatar
33 votes
5 answers
50k views

Creating fishnet grid Shapefile in QGIS?

How do I create a fishnet shapefile using QGIS? The equivalent task of "Create Fishnet" in ArcGIS.
bcollins's user avatar
  • 3,563
25 votes
7 answers
50k views

Filling holes in polygons 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....
J-Man's user avatar
  • 259
15 votes
4 answers
10k views

Setting default value for attributes in shapefiles using QGIS

In QGIS 2.14.6 I would like to define a default value for an attribute in a shapefile (or spatialite layer as well) which is applied if the user doesn't explicitly sets the value. Is there a way to ...
Jochen Schwarze's user avatar
10 votes
2 answers
9k 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 '...
Gonja's user avatar
  • 497
10 votes
4 answers
8k 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 ...
astaines's user avatar
  • 249
5 votes
5 answers
9k 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 ...
user29858's user avatar
66 votes
2 answers
148k 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 ...
Novice's user avatar
  • 661
41 votes
6 answers
30k views

Joining attributes from nearest point in QGIS

I have two layers with points, 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 a field ...
Fred's user avatar
  • 692
41 votes
4 answers
65k 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 ...
Laurent S's user avatar
  • 533
23 votes
3 answers
20k 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 ...
Rich's user avatar
  • 1,589
19 votes
3 answers
23k 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'...
Cao Minh Tu's user avatar
  • 1,994
15 votes
2 answers
22k 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.
mapperx's user avatar
  • 1,427

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