Geographic Information Systems

Questions tagged [qgis]

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

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25 views

Remove line self intersections?

I have a polyline that is self intersecting in some points and I want to create a "clean" version of it. Basically something like that Remove Self Intersections in the first image(single part). So ...
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0answers
37 views

Creating a greyscale topography map of the world on QGIS

I am looking to create a greyscale topography map of the world in QGIS which I can then output as SVG contour lines. Maybe there is somewhere where I can find and download greyscale vector tiles of ...
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1answer
20 views

Sharing WMS / XYZ / MapServer sources across multiple users / installations

Our organisation has multiple users using QGIS and using a lot of web-based ArcGIS mapserver / WMS data. At present we share links to WMS/WMTS, XYZ, ArcGIS Mapserver resources via Wiki, however it ...
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23 views

Checking if the data is entered on QGIS plugin UI created using QTcreator? [duplicate]

I have developed a plugin in QGIS 3.10 and now I need to integrate it with Django rest API. But I am not able to achieve this as I don't know how to retrieve the data entered in the plugin UI and also ...
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25 views

Creating many Google Maps paths and exporting to ArcGIS/QGIS

As part of my senior thesis, I have a CSV of about 500K unique combinations of starting and ending lat/long coordinates, each of which represents the starting and ending locations of bike share trips. ...
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21 views

Storing historical data

I am working on a project in QGIS where we would give the client QGIS and a dataset of their cattle station where they can investigate infrastructure development. One thing I am trying to figure out ...
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2answers
27 views

Creating arbitrary profile?

I am trying to create a transect profile and extract information for each specific bands of Landsat which will be further used to create a transect graph. Is there any direct way of achieving this ...
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1answer
26 views

Using input vector field in QGIS python script

I have created a QGIS Graphic Model using built-in Graphic Modeler. My model is supposed ask the user for an input layer, an overlay layer, and fields from the overlay layer. The model then should ...
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0answers
29 views

Creating flow velocity map in QGIS?

I want to make velocity map in this format. I have points with vector attributes (u, v and velocity), but my arrows have only heads!
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0answers
15 views

Control direction of lines around earth

in QGIS 3.4.14, I am trying to draw a line from Los Angeles to Tokyo. With an XYZ Tile base map turned on, the line goes east from Los Angeles (over Africa) to Tokyo. I would like the line to appear ...
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1answer
41 views

Advantages of using GRASS Tools in QGIS

Are there any advantages to the use of GRASS Tools (Creating a new mapset and using GRASS modules) instead of using GRASS algorithms available in the processing toolbar with QGIS Data? I think there ...
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3answers
99 views

Is there a hotkey for switching on/off a layer in QGIS

I would like to know if there is a hotkey in qgis for switching on/off a layer. I have a task where I have to open and close a layer quite frequently. Doing it by a mouse is too time-consuming and ...
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0answers
12 views

QGIS 3x Viewshed plugin no result after re-projection

Continuing the query here: QGIS 3x viewshed plugin returns wrong results for visibility map I was trying to set proper CRS for my DEM on the area, where I am currently working on. Unfortunately, the ...
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1answer
38 views

Enlarge the size of multiple polygons contained in a shapefile QGIS

I have a shapefile which contains many polygons and because I work on a large geographical extent, I'd like the polygons to be slightly bigger, for presentation purposes. Basically keep their extent ...
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17 views

Aggregate neighbor polygons by total area

In QGIS I have a layer of polygons, each with a different area. I'd like to group neighbor polygons in a way that each group's total area will be around a predefined value. Any ideas? Thanks!
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1answer
35 views

Installing Python modules for QGIS3 on Mac?

I want to install some third-party Python modules for QGIS3 on Mac, however, I have no clue how to do it, since I am not so much familiar with different Python environments. Is there any similar ...
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0answers
15 views

Detrending DTMs

I've been using the method for detrending DTMs given here (in Clause 10.3): BAJR The results are encouraging but I'd like to 'flatten' the underlying terrain even more. One of my DTMs has ...
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28 views

Visualising opening hours of a building with rule-based symbology [QGIS]

I have the shapefile of a neighbourhood of buildings. Within the attribute table of this shapefile I have the opening and closing hours of each building, written in decimal format (e.g. 10:30am is 10....
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1answer
19 views

Get layer by name, retrieve layer, in startup.py

I wrote a simple script in startup.py, but when I open a QGIS project, I appear a python error window. The "contratos" layer is a PostGIS layer. But I tried with a regular layer and the error persist....
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1answer
34 views

QGIS Add Polygon name as field to all points inside Polygon

I have a single polygon layer with multiple blocks features named "block 1" to "block 40". Within these polygons there is a single layer with multiple points. I want these points to get the block name ...
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29 views

Problem when combining raster in QGIS

I am trying to combine rasters corresponding to radiometrically corrected Landsat 8 bands with QGIS 3.4. Reading the internet I know that it is necessary to write the value 0 in the option "Input ...
3
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2answers
85 views

How to select features using an attribute which falls within a range

I want to select batches of features using an expression which gives a range of IDs to select. Instead of writing this "ID" IN (1,2,3,4,5) I would like to write something like this "ID" IN (1:5) I ...
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1answer
45 views

Adding button to QGIS toolbar by using Python and Macros in Project Properties

I've successfully created a script that adds a button to the plugin toolbar in QGIS, by running the script in the python console. Here is my code: import webbrowser icon_path = MyPath def open_url()...
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22 views

Time series for clustered NDVI data for each clusters to record the change analysis

For my master's project, I am using Google Earth Engine and I have some doubts regarding this. The main objective of my project is to calculate NDVI temperature for a specific area and detect change ...
4
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0answers
83 views

Does the projection of a PostGIS table affect the rendering speed in QGIS

I am interested to know whether changing the projection of a PostGIS table will affect the rending speed when viewing it in QGIS. I have two layers coming from QGIS which are exactly the same and ...
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0answers
23 views

QGIS / Add Query Builder Like Toolboxes?

I am wondering if it is possible to add the query builder to the QGIS window, like Toolboxes, without having to open the layerproperties all the time. Any ideas?
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1answer
25 views

Join Attribute Table with multiple owners with only one Parcel

I have a problem in QGIS. I have an attribute table (no geographical information), which contains owners of parcels and an ID for every row. Then I have a shapefile, which contains polygons and an ...
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0answers
28 views

Connecting to Microsoft SQL Server from QGIS

I can't connect my QGIS to SQL Server. This is my database: This is my connection configuration to QGIS If I press test connection it says "Driver not loaded". If i load database, there is ...
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3answers
53 views

Create a new grid layer from a CSV, given the four corner coordinates

I'm trying to add a new grid layer by importing it from a CVS file. In the CSV, each line represents a grid, and the coordinates of the four corners are given. Moreover, the grid contains its own ...
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0answers
15 views

QgsMapCanvas map rendering issue

Background : I am making a raster + vector map navigation application using Qt4 and QGIS in C++. Map is loaded inside QgsMapCanvas, which is quite slow, mapcanvas is the part of QGraphicScene, ...
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1answer
40 views

Removing raster values using a threshold in QGIS and interpolating

I have an imagery (plant cell density) comprising vine rows and grass inter-rows.I'm trying to permanently remove all the values of inter-row grass through setting up a threshold value. The vines ...
1
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1answer
52 views

Clip heat map so it does not extend past boundaries of another layer

I have the following heat map that was created from clusters of vector points. I have a second layer underneath this heat map that shows the U.S. How do we prevent the heat map from extending past the ...
3
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2answers
67 views

Draw lines between points

I am doing a research project for which I need to find an effective way for drawing lines between a number of points along a square. I need there to be a line between every point on the square in ...
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1answer
31 views

QGIS Layer Tree API crashing when removing layer

I'd like to change the order of layers in my layers panel using Python in the Python Console (this is a for a script not a plugin). Following a blog post here on the Layer Tree API for QGIS, the ...
5
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1answer
74 views

QGIS Labeling automatic callout-line small polygons

I have a polygon layer and want to create a automatic labeling. In this polygon layer are some pretty thin polygons. For this polygons the labeling should be placed outside of the polygon but with a ...
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0answers
34 views

Intersect lines in QGIS without Processing module

Currently I am able to perform intersection (split line at polygon boundary) between line and polygon using processing module in python script as QGIS module. Now I am interested, if there are another ...
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1answer
42 views

Copying attribute values to new layer in QGIS with python

I am making a buffer for a point layer and want the attribute values to be copied over to the new layer. I am able to duplicate the attribute fields, but not populate them with the values. I get the ...
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0answers
13 views

DotSpatial reprojection introduces offset compared with QGIS

Im writing a converter from shape file to Geojson using C# and DotSpatial to do coordinate conversion. Currently this mostly works, with newly created shape files in QGIS the coordinates are perfect ...
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1answer
34 views

Difference in length of lines computed with GeoPandas or in QGIS [duplicate]

So, first of all, here is a test file: https://we.tl/t-xqo5KyRlqD The column length was added using QGIS (v 3.10 A Coruña), field calculator and adding parameter $length. If the file is opened with ...
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0answers
13 views

LRS m dimension data view

I have generated 3D with LRS data using oracle spatial and trying to view in QGIS but it doesn't read that table from oracle database i did another try is that without 3D generated LRS in oracle ...
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0answers
19 views

Importing a CSV with GEOJSON column in QGIS

I have CSV files and each file has a geometry column using GeoJSON (some are polygons, some are lines and points). How can I import those files in QGIS3? ID polygon additional information point 1 ...
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1answer
22 views

Specify the adminsitrative level in QuickOSM

I am using QuickOSM to download the boundaries of cities into QGIS before saving each city data as a GeoJSON. QuickOSM enables the Key (in my case, 'boundary') and Value ('administrative) to be ...
0
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1answer
29 views

Export a map into a useable format for a design software - QGIS?

I have a general map of the Mediterranean Sea, showing all the countries I've considered in a study, with watersheds etc. I've tried to make it look nice, but I think it could do with a bit of extra ...
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1answer
42 views

Link QGIS CSV / Excel with raster layers

I have the following problem. I want to link a value from an Excel file to a raster layer. Uploading the Excel file and linking to other vector layers via properties -> linking is no problem. However,...
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0answers
17 views

After DXF conversion, layer with same coordinate and projection not visible

I've converted a DXF file to shp (using another DXF importer/convertor plugin). In QGIS this shp will open fine if standalone but is not visible when added to a project with other shapefiles. The xy ...
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0answers
36 views

How to covert a GeoTIFF DEM to a standard raster format without losing quality or resolution

I'm working on a project, a spin-off of my graduate dissertation, to digitize LiDAR data of a portion of Tampa Bay (20x20 km^2 at 1:1 scale) into a Minecraft map. Ideally I want not just accurate ...
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0answers
36 views

Slope analysis in QGIS [duplicate]

I have a 1/3 arc-second DEM downloaded from USGS that I am trying to use to create a slope analysis layer. The DEM is in ESPG 4269 to start and I've re-projected it into NAD83 UTM Zone 11N (the DEM ...
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1answer
49 views

Different colours for rings of a buffer

I am looking for a way to create a multi distance buffer and have each buffer a different colour. For example, a buffer around a point has 5 rings. I would like to have each ring a different colour ...
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1answer
30 views

QGIS rule based styling - rule ordering

I’m experimenting with some rule based styling which is working really well to a point but I’m hoping it can do more. I work in school transport I’ve plotted all pupils in a certain school on the map. ...
1
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1answer
52 views

The right way to convert GeoJSON to DXF using QGIS

I have a problem exporting GeoJSON to vector format. I downloaded GeoJSON of highway objects from OSM, opened it in QGIS, and then saved it as DXF. The problem is when I open it in CorelDraw, road ...

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