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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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Least cost network algorithm for graph with predefined topology on raster

I'm trying to transfer a graph with a predefined topology onto a cost raster to create a least cost pipeline network. The cost raster will be transformed to a undirected weighted graph with edges ...
banana store's user avatar
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1 answer
35 views

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", ...
Glic's user avatar
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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 ...
vdc's user avatar
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1 answer
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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:...
Nicolo Cappelletti's user avatar
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39 views

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 ...
Préliator's user avatar
1 vote
1 answer
56 views

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 ...
Biorix's user avatar
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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 ...
Biorix's user avatar
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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 ...
user231744's user avatar
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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 ...
AM-A's user avatar
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2 votes
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86 views

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 ...
eagleadmiral's user avatar
5 votes
1 answer
293 views

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 ...
Andy Baader's user avatar
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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 ...
Chamika Kasun's user avatar
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1 answer
31 views

GeoServer WPS vec:bufferFeatureCollection algorithm

For GeoServer WPS plugin vec:bufferFeatureCollectinon function, what is the algorithm that support such function?
user233292's user avatar
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1 answer
57 views

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 ...
Simon's user avatar
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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 ...
Pierre's user avatar
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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 ...
Jas Singh's user avatar
1 vote
1 answer
65 views

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 ...
winnewoerp's user avatar
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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 "...
winnewoerp's user avatar
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1 vote
2 answers
113 views

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 ...
ljden's user avatar
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1 vote
1 answer
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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, ...
h3rmit_purp1e's user avatar
2 votes
1 answer
52 views

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 ...
rablentain's user avatar
1 vote
0 answers
26 views

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" ^ ...
Duy's user avatar
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2 votes
0 answers
79 views

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 ...
Марина Лисниченко's user avatar
6 votes
3 answers
1k views

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 ...
stats_noob's user avatar
1 vote
1 answer
211 views

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 ...
Jorge Calvar's user avatar
4 votes
3 answers
139 views

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 ...
stefcud's user avatar
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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 ...
Nick Griffiths's user avatar
1 vote
1 answer
358 views

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,...
thus__'s user avatar
  • 179
3 votes
1 answer
664 views

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 ...
bjornasm's user avatar
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1 vote
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150 views

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 &...
Mahmoud Adel's user avatar
3 votes
4 answers
91 views

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 ...
Tom Brennan's user avatar
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1k views

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 ...
dmjf08's user avatar
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1 vote
0 answers
109 views

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 ...
Roman Dostál's user avatar
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0 answers
43 views

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 ...
lolololol ol's user avatar
3 votes
1 answer
138 views

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? ...
Babel's user avatar
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0 answers
43 views

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 ...
Anni98's user avatar
  • 107
3 votes
1 answer
181 views

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 ...
Taras's user avatar
  • 33k
2 votes
1 answer
135 views

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?
Jason's user avatar
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2 votes
0 answers
35 views

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 ...
sicadu's user avatar
  • 129
4 votes
2 answers
1k views

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 ...
Koray_Ozdogu's user avatar
3 votes
1 answer
308 views

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 ...
Caligraphy's user avatar
2 votes
0 answers
46 views

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 ...
Babel's user avatar
  • 71.6k
1 vote
1 answer
128 views

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 ...
DuckQueen's user avatar
4 votes
2 answers
248 views

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 ...
pete's user avatar
  • 1,101
2 votes
2 answers
943 views

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 ...
VicTorn's user avatar
  • 31
3 votes
3 answers
837 views

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 ...
swiss_knight's user avatar
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0 votes
0 answers
401 views

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 ...
Casper Bang's user avatar
1 vote
0 answers
128 views

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/...
zansan's user avatar
  • 11
2 votes
0 answers
55 views

Connecting points with Z values to lines where the Z values are retained in the nodes of the resulting line

I have interpreted seismic data as xyz-points (about 23 cm lateral resolution). They are not really ordered but rather a simple list of coordinates. One file contains multiple seismic "lines"...
Sascha K.'s user avatar
1 vote
2 answers
240 views

How can I cover an AOI with a subset of image extents?

I’ve been experimenting with a problem that I have not found a friendly and simple solution for yet. Curious to know if any of you have already solved this problem. Given a AOI and a set of image ...
Zachary Deziel's user avatar

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