Questions tagged [qgis]
QGIS is a cross-platform GIS application licensed under the GNU General Public License.
36,550
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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
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27
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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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33
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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 ...
- 121
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1
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111
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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 ...
- 41
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169
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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 ...
- 363
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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 ...
- 1,217
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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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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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1
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69
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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 ...
- 153
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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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25
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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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86
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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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48
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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
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1
answer
119
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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 ...
- 816
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85
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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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35
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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 ...
- 89
2
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1
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33
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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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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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1
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53
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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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29
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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 ...
- 143
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1
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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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28
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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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49
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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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29
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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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22
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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 ...
- 143
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37
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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: ...
- 97
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1
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36
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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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1
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36
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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
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171
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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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25
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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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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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41
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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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1
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25
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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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2
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30
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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 ...
- 153
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1
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32
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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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41
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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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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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26
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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 ...
