Questions tagged [algorithm]
A mathematical procedure used to solve problems with a series of steps. Algorithms are usually encoded as a sequence of computer commands.
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I am building photogrammetric software but problem is about accuracy [closed]
after processing (without GCP) point cloud it shows 1.5 meter shifting. how can i resolve it? can you suggest any algorithm?
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How can I calculate the arrival time of a bus on a specific route?
I'm creating an app to track the location of buses in my city. My goal is to show in the app how long it will take for the next bus to arrive at a selected stop.
Each bus follows a specific route, ...
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Model designer crashes when applying layer styles
I have a problem with the designer model.
I'm looking to automate the application of layer styles via the model designer. I have several layers over several years using the same style that I saved. So ...
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How to save file in algorithm window in QGIS
When I was using the following hillside tool from the "processing" and wanted to save it (as shown as follows), this tool's window would close automatically after I clicked "save", ...
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DEM update/interpolation algorithm from control points
Context: I have a reference DEM, and Icesat-2 points covering some parts of it. The DEM is from 2012 and the Icesat-2 points range from 2018 to 2023.
Goal: I am looking for a way to 'update' the ...
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No result from algorithm r.stats in QGIS
I don't understand why algorithm r.stats doesn't give me result in the sidepanel (show result); the error is 'impossible open the file'
What can I do to solve the problem?
I show you:
Versione di QGIS:...
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PyQGIS - Algorythm not found
I want to use the "Networks" extension on PyQGIS. This is correctly installed on QGIS 3.28 (QGIS installed with OSGeo4W) and works on the application.
Unfortunately, it is impossible to use ...
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Recursive model in QGIS
I needed to do an algorithm in the modeler and wanted to try (and also because I couldn't see any other solution) to make it recursive.
Unfortunately, now every time I try to just open the model to ...
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Set layer different style to multiple layer at once in model designer
I made a model that generates multiple layers
Among other entries, a style file is required as input that I use to set one of the output layer.
I would like to use a folder input and to set multiple ...
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QGIS Shortest Path Iteration
I have a large QGIS Fiber to the Home (FTTH) design with 727 address, my focus here is on the Lateral sections from the homes to the Handholes (shown in green).
The design roughly breaks up to four ...
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Calculating intersection of a line segment with a circle on Earth's surface from latitude and longitude coordinates
I'm working on a problem where I need to determine if a line segment between two geographical points on the Earth's surface, intersects with a circle on the Earth's surface, defined by a central point ...
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Existing Algorithms for label placement with callouts
I am thinking to answer the question here: Label placement with callouts in QGIS.
I want to implement a kind of algorithm in python that will create 2 different columns [X and Y] that will be the ...
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Using Conditional branch algorithm in QGIS Graphical Modeller
I have a question regarding using the Conditional Branch algorithm in the Graphical Model Builder.
I am building a rather complicated model with many branches but not every branch needs to be used ...
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Calculating distance between two points on line string
I have a line string and two points with me. I need to understand how to calculate the distance between two points along the provided line string. Also, note that in some cases, the provided points ...
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GeoServer WPS vec:bufferFeatureCollection algorithm
For GeoServer WPS plugin vec:bufferFeatureCollectinon function, what is the algorithm that support such function?
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QGIS Processing Algorithms Fail After Second Execution with "Algorithm not found" Error
I'm encountering a persistent issue in my QGIS environment where Processing Algorithms fail to run after the second execution, consistently showing an "Algorithm not found" error. This ...
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How to find a path that goes through all points of a 2d graph while alternating between X axis and Y axis
I know my title isn't very descriptive, i'll try to explain it better here.
Let's say I have a list of coordinates that is built as the following :
list = [ (0,0) , (1,0) , (0,1) , (1,1) , (2,0) ]
The ...
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Retrieving concentration values from Google Earth Engine
I am using a chlorophyll-a algorithm to retrieve chlorophyll-a and turbidity concentrations using different algorithms for a lake using Sentinel 2A (S2_SR). How can I determine the output ...
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Find nearest points on network inside QGIS Graphical Modeler
I create a set of regular points with random offset inside a test area polygon using the QGIS Graphical Modeler. This it what the result looks like:
Then I use the following expression (not yet very ...
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Accessing previous algorithm outputs in QGIS graphical modeler [duplicate]
I want to extract features by expression in a graphical model in QGIS. I want to use the overlay_touches() function to extract features that touch those of another layer.
I manage to do this "...
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Performance of RTK when observed satellites don’t correspond
When a rover receives observations from a base station (e.g. through NTRIP from a CORS network) it can perform RTK to reduce ambiguities in matching observations to get a more accurate fix.
What ...
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Generate a radius for a point, in order to count how many times a line passes through that radius
I am working on a project where I have to count the number of lines passing near a point. I plan to generate a radius around each point, since the lines do not cross the point, but pass close to it, ...
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Algorithms for finding nearest road
Having two LineStrings I want to know if they actually are the same gps path or not. I guess something like if the distance between these are lower than x for a few points I would assume that they are ...
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ENDISI calculate
I'm new to ArcGIS. Can someone tell me why my ENDISI always equal to 1?
My algorithms:
("band02.tif" - 16170.19 * (("band06.tif" / "band07.tif") + "mndwi.tif" ^ ...
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Seeking algorithm for polygon straightening
I have a polygon that looks like this:
I want to get a result that ideally looks like this:
The best that I can come up with is a polygon simplification using shapely in Python:
Which algorithm ...
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Clustering Algorithms for Geospatial Data
I am new to the world of Geospatial Analysis!
I am interested in learning about Clustering Algorithms that can be used for Geospatial Data.
For instance, suppose I have:
A shapefile for all ZIP Codes ...
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How to use v.net.path algorithm on QGIS?
I want to use the v.net.path (see grass documentation) from the QGIS processing toolbox. However, I do not know what the format of the input parameters is. The required parameters are:
Input vector ...
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Find areas distant from any points
I want to draw all areas that are far enough away from any single point of a layer, in this case they are Openstreetmap building=yes tags and I want to calculate the areas that are completely clear of ...
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Algorithm for breaking polygon into squares [duplicate]
We've got some code in our Java application that breaks up polygons into grids for a bunch of reasons. One is to more efficiently spatially index coastal regions (the bounding box tends to cover the ...
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How Neighbor Contiguity Algorithm actually works
I want to identify neighbors based on queen or rook contiguities in a programming language that does not have the feature yet. I know that tools like spdep, pysal, geoda, and ArcGIS all implement this,...
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Seeking algorithm for finding shortest path around obstacles
I am seeking an algorithm, not GIS software.
To find the shortest path between two points at sea with land between them, you can consider land as a polygon shaped obstacle between these. The concept ...
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How to check if there is an arc within a polygon (algorithm in geometry) [closed]
Now I have a polygon with arc like this:
I need to check if this polygon contains arc or not. How can I do that using geometry?
Clarification about the reason why:
I need to know how to detect in &...
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Calculating total ascents greater than 50m
Calculating total ascent is a relatively common GIS problem.
Given a set of height data (eg from GPS, or from draping a track over a DEM), I am interested in calculating total ascents where each ...
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Crash when running algorithm via PyQGIS plugin
I use a Python plugin which is working great on my computer. But on another one, I get an error at the execution of an algorithm from processing package in PyQGIS:
## Report Details
**Python Stack ...
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QGIS - Graphical modeler - output shapefile is not altered
Graphical Modeller
I started using Graphical Modeler in QGIS (learned about it few weeks back and I was really excited about this). Unfortunately (probably due to lack of skill) I cannot seem to make ...
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Convert radar parameters to polygon
I have the following list of parameters for a given radar:
Latitude
Longitude
Coverage lateral
Coverage horizontal
Max Range
Power Emitted
I would like to convert these parameters to some type of ...
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Identify the algorithm (not code) for QGIS native tools
The question
For someone with no knowledge in C++ (programming language used to write QGIS code), is there a way to identify based on which algorithms the different QGIS native tools are written?
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Merge vectorlayers and attributes in QGIS
I am writing a script to run in QGIS and one thing I am trying to do is to merge a row of layers and their attributes. So if one layer is overlapping with another there should be created a new object ...
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Creating custom processing tool (sibling of Batch Nominatim geocoder) in QGIS
I want to create a custom processing tool for geocoding in QGIS.
It will reproduce the "Batch Nominatim geocoder" geoalgorithm, besides several things:
another URL of a geocoder will be ...
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Use polygon lines to create masks
Given a tile (the cropped base map in the left) and polylines (red lines), is there any tool/workflow in QGIS to convert them into masks in the right?
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How to colorize hierarchically-ordered polygons?
I have to implement a solution for coloring a lot of polygons that are derived from a hierarchically-ordered dataset. The dataset can be compared to a family tree in terms of hierarchy. Most of the ...
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Detecting and making all connected lines in the same direction in QGIS
I have a list of straight roads segmented which has a unique "ID". I would like to detect connected lines in the road network and make them in the same direction instead of reversing them ...
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Zip output of QGIS Processing Algorithm
I want to make a script which
processes some algorithms with multiple layers as inputs
outputs some results in QGIS project
then save the layers as zip files in a specified folder
I have not been ...
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Output singlepart features by default for tools and algorithms in QGIS
In QGIS, many algorithms and tools return multipart geometries. For further processing, a conversion Multipart to singleparts is necessary. This is a bit cumbersome.
To make just one example: when ...
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Passing selected layer-feature inside QgisAlgorithm (in code)
In our algorithm, we do three steps:
call Algorithm A AlgoA,
takeResultLayer into lyr from AlgoA output,
for each feature of lyr we want to run Algorithm B AlgoB .
Code of my processAlgorithm looks ...
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Processing algorithm as expression in QGIS
I would like to be able to set an expression as the default value of an attribute (in layer properties-->attributes form) which uses an algorithm from the QGIS toolbox.
In this case, the algorithm ...
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PyQGIS 3: Cannot Pass Memory OUTPUT To Next Processing Algorithm As INPUT
I am attempting to convert some ArcGIS arcpy command-line scripts to PyQGIS and am running into a problem working with memory layers. The script takes several vector files as input and progresses ...
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Finding largest circle which entirely included in multipolygon and not containing any point of points layer
I have two layers*:
1 MultiPolygon (the complex green features)
1 MultiPoint (many thousands of yellow dots)
How can I efficiently find the largest circle (center coordinates + radius) which is both
...
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Seeking algorithm other than Convex-Hull to avoid overlapping polygons
I want to draw polygons with no overlap, based on sets of points. If I use Convex Hull algorithm to deduce the boundary polygon, it's pretty obvious that the resulting polygons WILL overlap. Is there ...
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Least cost path algorithm in SAGA?
I'm very new to this topic.
I have to calculate the least cost path between two points for a school project and found this tutorial: https://dges.carleton.ca/CUOSGwiki/index.php/...
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