Questions tagged [qgis]
QGIS is a cross-platform GIS application licensed under the GNU General Public License.
6,447
questions
14
votes
3
answers
23k
views
How to create an "area of interest" polygon mask?
I've created a GP tool using ArcGIS that creates an "area of interest" mask from selected features. Effectively it creates a new donut polygon layer where the hole was the previously selected ...
14
votes
2
answers
48k
views
How to select a multiple field value by expression from the same layer in QGIS?
Using QGIS in the operation 'select by expression' how is the correct expression to select multiple field value? ex. City NAME = ROME and NAPLES (expression is invalid)
14
votes
5
answers
18k
views
How to sum up pixel values in QGIS?
I need to know the value of the sum of all pixels in a raster. However, in the Statistics section of the Metadata tab in Properties, under Sum of All Cells it always indicates 0.00. I have tried with ...
13
votes
4
answers
2k
views
Showing the bounding box for every coordinate system in QGIS
I'd like to visualize where every coordinate system in QGIS is in the world. I can see the bounding box for them when I go to QGIS and select coordinate system:
But I'm trying to figure out how to ...
13
votes
4
answers
14k
views
Splitting lines into equal segments with QGIS
I'm attempting to split a curved (wiggle) line into equal length segments. Have used Grass's v.split which works to a degree but does not provide the output I'm after.
v.split will extract segmented ...
13
votes
7
answers
55k
views
Shapefile layer no longer editable (toggle edit option greyed out) in QGIS
I am using QGIS 2.16 / Windows 10.
I have a point shapefile which I have been using for a little while that has always been editable.
Today I was editing the layer, saved my edits and left my ...
13
votes
1
answer
12k
views
Creating Dot Density Maps in QGIS?
Is there a 'friendly' way to create dot-density maps, where a polygon attribute data defines the number of dots (e.g. 1 dot = 100 ) using QGIS 1.7+? I say friendly because after a couple of hours ...
13
votes
4
answers
11k
views
Is it possible to connect to ArcSDE using QGIS?
Is anyone aware of any plugins, or any other way to connect and view data from an ArcSDE database in QGIS desktop?
13
votes
3
answers
3k
views
How to ignore "handle bad layers" in QGIS?
I have a QGIS (2.14.3-Essen) project that I use both at work and at home. I keep all but two layers with the project.
The two remaining layers are very large - a DEM and hillshade totaling more than ...
13
votes
3
answers
30k
views
How to digitize building footprints with orthogonal edges?
Using QGIS, I am trying to digitize an old raster map, and because I ultimately want to load these 2d layers into sketch-up to turn into 3D models, I need everything to be square.
Here's a sample of ...
13
votes
2
answers
5k
views
Differences between different georeferencing transformation algorithms in QGIS
Expanding on Transformation types in geo-referencing of QGIS?, I'm trying to understand the exact transformations used by QGIS, and how they differ. The georeferencer documentation is of course a good ...
13
votes
1
answer
11k
views
How to Uninstall QGIS from MacOS
As many probably know, the MacOS installer for QGIS is not as turnkey as the windows version. You have to basically install 3-4 sets of packages, only one of which end up in the Mac apps directory (e....
12
votes
2
answers
16k
views
Summing polygon area by category using QGIS
I have a vector layer of habitats. Each feature belongs to a category and has its area calculated. I'm trying to find out the total area of each type of habitat.
I've looked at QGIS "Statistics by ...
12
votes
2
answers
6k
views
Is there a way to split polygons by several lines in QGIS?
I have a polygon (.shp) and a line (.shp) layer. I want to split the polygon in several pieces along the lines that overlap the polygon. Afterwards I want to edit each polygon separately (attribute ...
12
votes
1
answer
2k
views
Assigning shortcut to PyQGIS script in QGIS
Is it possible to assign a keyboard shortcut to a (custom or not...) script of the Processing Toolbox in QGIS?
I have not found any information about it so far.
12
votes
2
answers
9k
views
Empty vector menu in QGIS on PC with French as default language
I installed QGIS 3.0.0 on a PC with French as default language. After changing the language of QGIS to English, the 'Vector' menu is empty and there is a French 'Vecteur' menu.
Any ideas how to fix ...
12
votes
4
answers
5k
views
Making segmented roads appear as one line in QGIS?
I am footling around with QGIS and the British OS Strategi dataset. If I render the roads with a simple line style they look fine:
However, if I apply something slightly fancier, it looks wrong, ...
12
votes
3
answers
5k
views
Styling discrete raster using QGIS?
I have rasters with discrete values (Landuse categories, boolean values...). I would like to be able to style them in a discrete way:
0 -> Red
1 -> Blue
2 -> Green
...
I wish something like ...
12
votes
2
answers
9k
views
How to format labels with leading zeroes?
I'm trying to display a number next to a symbol in QGIS 2.0.1 - The numbers are from an integer-field in a PostgreSQL database.
The goal is that single digit numbers get a leading 0 (zeros). Examples:
...
12
votes
1
answer
2k
views
How to visualize measure values along linestrings in QGIS?
I have a series of LineStringM geometries. The measure value represents slope (or stream gradient) at each point in the geometry. I love QGIS's robust styling options, but I can't find a way to render ...
12
votes
2
answers
4k
views
Clipping raster-image increases file size
Working with QGIS 2.4.0 Chugiak I have a question regarding the clipping of raster images. I have an aerial picture that I want to clip using the extents of a shapefile. So far so good, I used the ...
12
votes
3
answers
3k
views
How to calculate how many polygons I can put inside a polygon?
I usually use QGIS.
I explain my problem with an example:
there is a forest (irregular geometry1) and one tree (geometry2).
I want to know the maximum number of trees that the forest can contain. ...
11
votes
5
answers
47k
views
Breaking single polygon into multiple polygons? [closed]
I created voronoi polygons after which I dissolved them on the basis of one attribute. Now there are cases where in for one single attribute "abc" I have3 polygons at different places with same object ...
11
votes
3
answers
3k
views
Summing up values of neighbouring polygons using QGIS?
I hope that you can help me with the following problem: I have a vector (polygon) layer. I would like to add an attribute to the layer that - for every polygon - sums the values of a specific field of ...
11
votes
2
answers
2k
views
Converting polygon to lines without duplicate edges?
This seems like it should be easy, but I'm not figuring it out: How do I convert a polygon layer into a line layer representing the polygon edges, where each edge belongs only to a single feature (or ...
11
votes
5
answers
5k
views
How to place labels under a vector layer? [duplicate]
I want to place the labeling under a layer. In QGIS 2.2 apparently the label appears automatically at the top. Can someone help me. (see attachment)
example:
11
votes
1
answer
4k
views
QGIS Modeler if/else condition, custom script for Modeler
I want to make a simple if/else function inside my Model and I wanted to know if it's possible or not.
I want this thing to do that if an Input for 'Segment Layer' is selected that it
doesn't have ...
11
votes
1
answer
1k
views
Determine roundness of polygon in QGIS
Suppose a polygon layer in QGIS with differently shaped polygons (no multi-geometries, let's keep it simple). Is there a way to calculate some kind of roundness characteristic of the individual ...
11
votes
2
answers
7k
views
Why can't I edit KML/GML layers?
Newbie here confused by my first experience in QGIS
I have a handful of lines defining a bike route.
Originally they were saved in a .gml file and later translated into .kml so they could be viewed ...
11
votes
1
answer
11k
views
Is there any other option to display DMS grid and graticule in QGIS Print Composer?
Is there any other option to display DMS grid and graticule in QGIS Print Composer, since there is no plugins available yet?
11
votes
2
answers
18k
views
QGIS Raster Layer - Black rectangle appears as background
I have looked at solutions to what seem to be somewhat similar problems but they don't seem to solve my problem. A georeferenced raster layer loads into the correct location in relation to other ...
11
votes
2
answers
11k
views
How to get attribute values of another layer with QGIS expressions
The question: How is it possible to get the value of an attribute in another layer?
What is clear: When using QGIS expressions on a layer, it is possible to relate to features of another layer with ...
10
votes
2
answers
4k
views
Adding coordinate system to layout in QGIS composer?
I would like to know if there is a way to add a dynamic coordinate system field into a QGIS composer layout.
I can use an expression to add many items such as document name, file path, etc but I can;...
10
votes
1
answer
2k
views
QGIS: Map theme with layer visibility AND style, does it exist?
I'm using QGIS to do urban visualisation on large scale territory, I'm used to working with Archicad which has an amazing option called "Graphic Overrides", it's a way to create different ...
10
votes
3
answers
34k
views
Create a Raster file out of a ASCII grid file?
I'm using a special system to do geomagnetic surveys. The software let's me output the information as image files, ASCII grid or in its own proprietary file format.
Now I want to get its information ...
10
votes
3
answers
4k
views
Does QGIS have WMS-T (WMS with time) support?
Does anyone know if there's support for WMS-T in QGIS?
Through the app I can add WMS layers, but I can't work with WMS-T (there's no place to set the time parameter).
I been going through the the ...
10
votes
3
answers
7k
views
Find nearest line feature from point in QGIS
I have a line feature set and point feature set. I want to get the nearest line feature from every point. For this, the line features are converted to point using "Extract Nodes" tool. Then ...
10
votes
2
answers
1k
views
QGIS 2.14.6 Processing Extension, 'Polygonize' Tool missing
Just installed QGIS 2.14.6 64Bit from OSGEO4W installer. Processing extension Version is 2.12.99. As can be seen in the screenshot, I'm not able to switch to 'Advanced Interface' as usual in order to ...
10
votes
1
answer
4k
views
Add layer to existing geopackage not working in QGIS?
My organisation uses mainly ArcGIS and we have a need to share data with contractors. I recently introduced QGIS (because one of our application uses WKT to import geospatial data and QGIS makes the ...
10
votes
2
answers
9k
views
Creating curved labels in QGIS
I added an image, that explains my demand (see Schiefelsbach river).
How can I do this?
10
votes
2
answers
18k
views
Finding length and width of polygon in QGIS
How can I find polygon's length and width in QGIS (regular polygon and irregular polygon)?
I have area and perimeter but not length and width.
10
votes
2
answers
35k
views
QGIS Multiple CASE WHEN/THEN Statements for Expression Based Labels
I am trying to label a single point with multiple labels, based on the attributes for that point. For example, if one of the attributes is equal to 1, I want to label it with a specific text string; ...
10
votes
3
answers
50k
views
Which CRS to use for Google Maps?
I am trying to map a Shapefile (download) onto a Google Map using the Javascript API. The Shapefile describes the boundaries of NYC School Districts.
The file's projection was Lambert Conformal Conic,...
10
votes
4
answers
2k
views
Comparing areas in scanned historical land use maps using QGIS?
I am a relative beginner to using GIS, and am running QGIS 2.0.1 in Linux. I have two historical maps which I want to analyze, that show land use patterns in the same area at two different moments in ...
10
votes
2
answers
4k
views
Extracting pixels from a raster based on a given tolerance value as in Photoshop
I'm new with raster in QGIS. I have a three-band (RGB) georeferenced raster similar to this: (Reference)
And I would like to extract the pixels with similar color like in the following image by given ...
10
votes
2
answers
9k
views
How does manual Label Placement in QGIS 1.9 work? [duplicate]
There are a bunch of questions here related to labeling in QGIS, but it's not clear which version they are referring to, and I know this is something that has changed recently. Hopefully it makes ...
10
votes
5
answers
36k
views
Opening ArcGIS Desktop layer package (.lpk) file using QGIS on Mac?
I downloaded an LPK file from the Esri site that contains USPS defined zip codes. I'm working with QGIS on a Mac, so I converted the file to a .zip. There's a .lyr file that opened up in the zip, but ...
10
votes
2
answers
33k
views
The following layers were not correctly generated. Grid
I keep getting the same error:
The following layers were not correctly
generated.GridYou can check the log messages to find
more information about the execution of the algorithm
I saw two ...
10
votes
2
answers
1k
views
Data defined label position for more than one scale in one layer
I'm looking for a better labeling-solution for my projects. It seems to be difficult - but maybe I'm just blind?
My projects:
I build printed bike-hike-books. The main scale is 1:75k and there are ...
9
votes
4
answers
7k
views
Removing green Xs and red lines in QGIS
I'm using QGIS 2.18.15 and have somehow ended up with the following on my screen. I've deselected every layer and these green X's and red lines persist. I cannot "undo" to remove them.
What ...