Questions tagged [qgis]

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

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How can you georefernce rasters on the fly in QGIS

How can you georefernce rasters on the fly in QGIS. In ArcGIS Pro when I start georeferencing and adding control points the raster will start to shift as I’m plotting the control points. So I can see ...
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QGIS Plugin executing function with parameters

I'm creating a QGIS plugin that will load specific layers from our server, so inexperienced GIS users (e.g., upper management) can access key, up-to-date, layers with single clicks. I've created the ...
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Selecting polygons within multiple polygons [closed]

I have three sets of data: District (polygons) County (polygons) Cadastral lots (polygons) Now, the districts and county layer are coded numerically. Due to some human errors made previously, there ...
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3 answers
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Extract lines not connected to railway network

I want to extract the lines which are not connected to whole railway system (see picture). These are smaller service and leisure lines of minor importance. I thought about something like "has not ...
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QGIS - Resolution issue

I have 2 images. One of them was using a custom CRS that had pixel of 463m. I used warp(reprojection) on this and used the epsg4326 CRS. This then converted the image from 463m pixel to 0.00205 pixels....
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CRS to use for computing distances between points on global scale with GeoPandas

I have a global coastline grid made up of polygons (hexagons) and I am trying to aggregate global data onto these hexagons. For example, I am trying to compute the distance of each hexagon to the ...
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Bad geometry for buffer in QGIS

I've generated some routes with the Network Analysis: Shortest Path (Layer to Point) from the Processing Toolbox (PT). Route files are GPKG. Now, I am trying to get the tapered buffer, also from the ...
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Export Atlas - Different data - Same canvas

On a defined study area, I have thousands of geotagged information. I would like to export an Atlas of these data, each export displaying one information. (Ex: The location of each point for the ...
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Building QGIS. Is Qt6 supported?

I am in the process of building QGIS from source (https://github.com/qgis/QGIS) for Windows 10. I am using QtCreator 7.0.2 based on Qt 6.2.3 (MSVC 2019 , 64 bit). Does the current source for QGIS ...
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8 votes
2 answers
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Nearest polygon that differs on an attribute

I have two polygon layers: city blocks (black outlines) and city zones (multi-colored areas) shown below. I would like to find for each city block, the nearest block that is in a different zone. I've ...
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Create single polyline from a road network

I often need to create KML with a single polyline in order to organize bicycle riding group activities, sharing the KML so that every rider has the right path for that activity. I usually trace the ...
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Merge two shapefiles on QGIS

I'm new to the software! I am trying to merge these two polygon layers I downloaded as shapefiles: https://www.arcgis.com/home/item.html?id=95f1885eff9a4c089012a872c851c50a https://www.arcgis.com/home/...
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gdal2tiles.py Differs from Original Raster

When comparing in QGIS the output of gdal2tiles.py to the raster from which the tiles were generated there is a clear difference. In this image Pink is the gdal2tiles.py output, green is the original ...
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QGIS - How to check if a raster has same resolution as another raster with a different CRS?

I have an original raster file called SAM. This has a resolution of 0.0025 pixels, it was obtained using 100m resolution satellite. I have another raster called Global fire. This has a pixel ...
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1 answer
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Symbology lettertype

Does anyone know how to increase the lettertype when I am working in the print layout to export it as an image? My symbology in my normal working mode I have lettertype 10 (which is big enough to read)...
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Plotting GPS velocity field and ellipse error in QGIS 3.26.1

I am a beginner in QGIS and I do not know how I can plot a GPS velocity field as well as ellipse errors (text file) in QGIS. How can I do this?
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Sort SHP features by feature ID in QGIS

I have a shapefile which does not have any ID column. I put them in a validator, which indicates the ID of faulty features, based on the DBF line order. But by opening the shapefile attribute table in ...
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How do I select features with the same values but different IDs from a layer's attribute table in QGIS?

I have a multipolygon layer with several regions (green circles) that are identified through numerical fids. Within each region are multiple points (orange dots) with individual pointIDs. See example ...
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3 votes
1 answer
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Using QGIS expression with overlay_nearest() function to create line connecting point to two nearest points of other layer

I have in QGIS ver 3.22 two point layers named: source_p target_p I want to point automatically with a line from the source_p layer to the two nearest points on the target_p layer. Manually, I was ...
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QGIS2web fails to preview or export

I'm trying to export a map for OpenLayers. Unfortunately, the preview window will only show the tools and my background color. This is also true of exported files when viewed via export.html ...
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Problem with sDNA plugin setup in QGIS

When I open QGIS, a label appears: "Please ensure sDNA version 3.0 or later is installed ensure the sDNA installation folder is set correctly inProcessing -> Options -> Providers -> ...
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1 answer
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Getting bus routes departing from bus stop from OpenStreetMap data to QGIS

I design a map, where I want to depict the number of public transport lines that are in walking distance from each building block of a city. How do I give each stop its routes and its total amount of ...
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4 votes
1 answer
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Get print layout's item width and height in PyQGIS

I'm trying to create a function that will return the width and height of a print layout item. This one doesn't work. from qgis.core import * from qgis.gui import * @qgsfunction(args= 'auto' , group='...
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2 votes
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Newly created multipolygon layer fails to save due to large file size

I used the function "Join attributes by location" to join a number of polygon circles (a multipoylgon layer) with the values of the points (multipoint layer) that are "contained" ...
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3 votes
1 answer
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Get coordinates of a print layout item in QGIS

I would like to get the x value of a certain item from the print layout. In fact, my others print layout items depend of the position of this item, and this is why I would like to be able to get those ...
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1 answer
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Connect QGIS with PyCharm

I don't get the concept of developing with Python in QGIS. There is a Tutorial in the QGIS docs how to setup PyCharm for developing standalone scripts or how to develop custom applications. The first ...
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Approximate value of properties based on sold properties in the area

I have a polygon layer in QGIS containing the parcel data for a city and surroundings, and a point layer with information about properties that have been sold recently. Since there are far fewer ...
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2 votes
1 answer
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Classify the image by a field in its attribute table using QGIS software

I created the attribute table of raster data in ArcMap software. There is a field that I added in the attribute table that I created. I can reclassify the image using the field I added to the image's ...
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2 votes
1 answer
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QGIS How can I transfer atributes from one layer to another when those layers do not share the same number of features?

I am trying to add the most populated towns within a number of regions as an attribute to those regions. IE, I want a column on the polygon sheet listing the most populated town in that polygon. I ...
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2 votes
1 answer
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Create a singlepart polygon with several polygons in QGIS

I would like to create one polygon including others polygons that has an ID < 16 . The yellow polygons have ID < 16 and I would like to create a polygon like this: EDIT : I do not want to get ...
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Get feature from WFS based on the location from points

I have several hundred GPS points which I want to join additional data to (e.g. corresponding district). Since the points are spread over a whole country it seems not possible to pre-load every ...
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2 votes
1 answer
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QGIS - How do I select features in a particular location precisely, the location is a raster

I have polygon data that is data retrieved across whole world, how do I focus this data on a raster map. Basically I want to select the features only in this area but I want it to match exactly this ...
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Adding CSV file by Python to QGIS throws #Line20 got ...columns instead of... error

I am struggling with the following code: import numpy as np c = np.genfromtxt('C:/path/to/file.csv', delimiter=',') # check delimiter lats = c[:,0][1:] lons = -c[0][1:] # remove minus if you get ...
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Build a super lightweight version of QGIS

I'm looking for a way to create a QGIS build with a minimal set of specific tools. I want to use it with my custom script that allows the user to: Create a new project Add offline OSM tiles Put a few ...
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QGIS: Set CRS for vector tile

All vector tile sources that are supplied in EPSG:3857 WGS/84 are projected fitting to other layers, even when converted to other CRS using on the fly projection. There is a vector tile source that is ...
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Raster Singleband Pseudocolour Symbology keeps changing automatically in QGIS

I have a set of values from -87 to 77 in my raster and I would like to group them into different categories. When I make the classes manually (picture on the left) and select apply, QGIS automatically ...
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1 vote
1 answer
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gdalwarp to change my raster extents

I'm trying the gdalwrap command to set center and change the extent to -180 to 180. But for some reason, the bounding value is set but the pixel values are not transferred. This solution not working: ...
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1 vote
1 answer
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Setting the right projection for a georeferenced PNG image

I have been trying to georeference an image I downloaded from Google API. Here is how I approached it after many unsuccessful attempts: I calculated the coordinates of the corners using this code. I ...
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-2 votes
1 answer
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Count amount of buildings (floating polygons) within neighbourhoods

I want to count the amount of buildings within my neighbourhoods. The dissolve function doesn't work here because the buildings are not intersecting. Does someone have a tip on how I can do this?
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2 votes
2 answers
171 views

Calculate the percentage of a polygon either side of a line

I have a series of polygons outlining distributions of various fish species around Australia. I am relatively new to GIS. I am trying to class each species as either tropical or temperate based on the ...
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Move layers from a qgis project to an other

I was working on a non georeferenced qgis project and when I tried to drag and drop the layers from this project to a new georeferenced raster layer the other layers didn't show up. Some notes: The ...
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QGIS Join by location results in NULL fields

I try to join data by its position. I have one layer with GPX data as points and another layer managing zones as polys. I wanna get the data from the poly where the corresponding point is within and ...
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5 votes
0 answers
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Getting maximum of raster in QGIS and use it in another algorithm

I am developing a QGIS model in which I need to get the maximum of a raster. The Zonal Statistics makes a new layer, which I don't need. The html with stats is also not useful. I just need a numeric ...
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0 votes
1 answer
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Insert values from one polygon layer to another in QGIS

I have two polygon layers of the same area, which represent census subdivisions from two different census years. Between the two census, the precision of the polygons has improved a bit, so that the ...
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2 votes
1 answer
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QGIS Points show up for one field/value but not another

When I added a csv file as a delimited layer, it shows up on the map fine: I classified and changed the symbology of one field/value for bottom depth data and it worked fine too: When I tried to do ...
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1 vote
2 answers
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Substrat values from two polygon tables according to maximum polygon overlap using Postgis

I have two polygon layers/tables in QGIS. The two layers represent (almost) the same spatial division (census boundaries). Basically, the polygons don't perfectly overlap because of differences in ...
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2 votes
1 answer
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Toggle display of unplaced labels with PyQGIS

I am making a script that works with labels. Is it possible to turn on/off the display of unplaced labels with PyQGIS?
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2 votes
2 answers
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QGIS - Converting Vector to Raster and back to vector to resample resolution of vector data

I would like to convert my polygon data into a raster file to change the pixel resolution and then would like to convert it back to polygon data since this will allow it to be resampled to another ...
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0 votes
1 answer
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Keep only one nearest OD link (QNEAT)

I've made a distance matrix from one point layer (layer A) to another (layer B) using QNEAT. I got a web with links from every point from A to every point from B, but I don't need that many links. I ...
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1 answer
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QGIS Clip Raster by Mask Layer resulting in black image

I am trying to clip a 6 band Micasense Altum image which is in Uint16 format, with 5 multispectral bands and a thermal band which is lower resolution. The image was aligned using the micasense ...
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