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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Network Analysis Shortest path with original line segments as output

I've managed to batch run the shortest path algorithm and the shortest route (point to layer) in the output is perfect, except that I really need the individual attribute tables of the line segments ...
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Processing script in QGIS 3: Merging layers created by earlier algorithm

I'm writing a script using the processing framework (QGIS 3,12). Creating a buffer around a points layer using table_with_buffers = processing.run('native:buffer', params3, context=context, feedback=...
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Nearest Neighbor Global matching

I'm trying to compare two datasets; a satellite image and some known points. In the satellite image I've got 20 to 50 detections that should match up to a set of lat/lon points that I have. There is ...
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1answer
34 views

Classification with different data dimensions

I am trying to use the continuous change detection classification algorithm (ee.Algorithms.TemporalSegmentation.Ccdc() and it appears to be working for me, however when I get the results the data type ...
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26 views

Calculate mercator map pixel size from viewport

What is the algorithm to calculate the pixel size of the entire mercator map. Known information (see image): Viewport's Upper-Left corner (Lat, long). Viewport's Lower-Right corner (Lat, long). ...
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Creating Least Cost Path with cost distance analyse

I'm trying to create Least cost Path analyse between two points in QGIS. I had DEM and from this I created Slope with various elevation values. Then I made two points with different layers. Both of ...
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Least Cost Path: interpretation of results

I am using QGIS 3.10.2-A Coruña and its built-in Python Console. I am currently trying to compute least cost paths between combinations of 2 points given a road network layer. For this I am using ...
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50 views

Geospatial algorithm to create area midwayboundaries from lines?

I am trying to find out if there is any existing geospatial algorithm (in any open Open Source Geospatial software) that would allow to use a network of lines as a start point and expand those in such ...
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1answer
49 views

Input parameters for i.topo.corr algorithm in QGIS Python console

I'm trying to run the i.topo.corr algorithm in the QGIS Python console, on a multi-band WorldView image. I'm still getting an error that the input value is incorrect. For this algorithm, the inputs ...
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Total number of cells on each MGRS grid level

I'm trying to figure out how MGRS grid looks like in a whole. I've already read wiki page and some articles but still didn't find the answer to my question. As I understand: level (100 × 100 km ...
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1answer
86 views

Difference between ST_Simplify function in PostGIS 3.0.0 and PostGIS 2.5.3

Faced such a problem (or maybe it's a bug). I get different results when using the ST_Simplify function in PostGIS 3.0.0 and PostGIS 2.5.3. There are source data that are simplified by using a query: ...
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How to find similar GPS tracks considering timestamps?

There are around 300 users tracks per day with about 4k points in each with 10s time interval. I'd like to find similar tracks considering location and time. The tracks are similar if it can be ...
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How to store / what algorithm to use to find closest points from a given set of points to a polyline layer

I have a polyline layer and a points layer with features that are nearby the polylines. For the latter I want to find the closest points on the polylines (as existing vertices or new-created vertices ...
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Multiple centroids of complex outline polygons by recursive buffering

How can I algorithmically determine multiple centroids for overlapping (dissolved), very irregular regions representing canopy outlines? This is effectively a forestry issue. The context is that I ...
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1answer
59 views

Find minimum number of polygons connecting two points

Given GIS data of polygons and two points, is there a way to find the minimum number of polygons you need to traverse to walk between the two points? Even an approximate approach would be fine for my ...
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48 views

Calculate where a geodesic line crosses a meridian

Given a geodesic line between two points with known coordinates on a sphere, is there an easy way to calculate or approximate where this line crosses a specific meridian? I want to calculate where ...
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1answer
49 views

Perform Tile Index on Newly Created PDFs using PyQGIS

The python code below successfully performs the tile index algorithm on all PDF files stored in sub-folders named !pdf's within my V:Drive. A list of all paths to each PDF exported from QGIS is ...
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48 views

Getting Omniscape analysis ERROR: LinearAlgebra.LAPACKException(3)?

I am currently running landscape connectivity analysis with Omniscape, but I get this error : ERROR: LinearAlgebra.LAPACKException(3) Stacktrace: [1] chklapackerror at /builddir/build/BUILD/julia/...
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1answer
101 views

How to calculate line complexity index

I'm wondering if there is any suitable algorithm that can I use to calculate line complexity index (or indicator)? By "line complexity" I mean how many bends (direction changes) that line contains and ...
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21 views

Drawing equal paths from geographic points?

I have 10'000 geographic points (POS), 10 salesmen, and one starting point. To avoid discrimination between salesmen, everyone should travel the same distance and the same number of points of sale. ...
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1answer
50 views

Calculate position to put box into another container?

there has a big box, and the big box already contains many small box, then should place a new small box into the container. How do I calculate a big enough space to place the small box? There ...
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3answers
125 views

Splitting Streets to Create Polygons?

I have a need to take all the streets belonging to a certain area (in OpenStreetMap) and split each street by each other and form polygons from the segments that result from the split operation. I do ...
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37 views

Splitting linestrings based on their curvature

I'm looking for a method to split linestrings based on their curvature, more precisely if part of them could be considered a street corner. For example in the screenshot below, I'd need to split the ...
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1answer
226 views

Adding new attribute field to processing output algorithm in PyQGIS?

I have a processing script that will carry out a selection by expression of the input layer, then do a join attributes by location with a join layer. The next stage will be to add a new field and ...
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1answer
31 views

qgis:deletecolumn in QGIS 3 graphical modeler

I want to use the algorithm qgis:deletecolumn in a graphical modeler. How do I have to fill the case Fields to delete : ["field1","field2"] "field1","field2" field1,field2 [field1,field2] And is ...
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Getting minimum distance of points with scalable algorithm

I have a number of geographical coordinates with latitudes/longitudes: id | name | lat | lon 1 | New York | 40.730610 | 74.0060 2 | Philadelphia | 75.1652 | 39.9526 3 |...
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Simplifying Multiple neighbouring Polygons, removing gaps and overlaps

My main goal is to simplify multiple polygons, avoiding overlaps and gaps between them. My initial approach was: Find intersections for each polygon so that I end up with an array of polygons, each ...
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1answer
197 views

Performing isochrone in PostGIS by pgRouting?

In pgr_drivingDistance for isochrones the person who answered, missed to say the explanation of the answer about what function used by him to get the output for isochrone. I want to do the same but I ...
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48 views

What is the complexity (big / little o) of the ArcGIS watershed delineation algorithm? [closed]

I'm curious about the complexity, in terms of Big or little O notation, of watershed delineation algorithms that are implemented in ArcGIS. I imagine that these will be dependent on either the size ...
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34 views

Seeking method for determining survey points?

I'm trying to write software to create a topographic map, my goal is to select several points of interest and create a minimal mapping that is inclusive of the points and interpolates the topography. ...
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160 views

How to create equidistant points along lines (network)?

I am trying to create points at every X meters along a set of lines that represent a network. As suggested in QChainage doesn't place points evenly along dissolved lines I managed to this ...
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1answer
711 views

Client-Side Polygon split

I wanted to know if there is a way to split a polygon using JavaScript. So I have a web map which uses Leaflet API, and the user needs to cut polygons which are shown in the map using a straight line. ...
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160 views

QGIS Python AttributeError object has no attribute 'pushVersionInfo'

I am unable to use almost all of the processing toolbox features in QGIS. I keep getting the following Python error across multiple algorithms: AlgorithmDialog.py", line 208, in runAlgorithm self....
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38 views

Algorithm(s) for Sensor Footprint at limbs

Is anyone aware of algorithm(s) that have been developed for computing remotely sensed image footprints that handle body limbs? The limb is the edge of the body / atmosphere where only the blackness ...
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Algorithm “qgis:difference” returns multiple heterogeneous outputs

I use the qgis:difference algorithm but it returns multi-type outputs. Sometimes it's a QgsVectorLayer but sometimes a str such as : output_.... My question is : when the algorithm returns an empty ...
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1answer
216 views

Match linestrings using Fréchet distance

I have two datasets of roads (both in WGS84). One has nicely digitized geometries, but lack some of the attributes and the other has heeded attributes, but digitized terribly. I want to transfer ...
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1answer
43 views

How is IDW raster formed?

IDW algorithm says that it makes a grid and assigns value to each point in grid depending on the distance of separation. From this definition, it looks like the output is set of equally spaced points. ...
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2answers
152 views

PYQGIS 3 Using the ouptut from GRASS v.distance algorithm

I have a script which is trying to run v.distance on two existing shape files, buildings.shp which containing some polygons and singleasn.shp which contains a single point. This will be run from the ...
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1answer
271 views

What algorithm is used by the $geowithin operator of Mongodb

MongoDB can perform geospatial query such as finding restaurants inside region with the operator $geowithin. For example: db.places.find( { loc: { $geoWithin: { $geometry: { ...
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371 views

Finding algorithms of QGIS commands?

I'm looking for the algorithms (the math) used by QGIS but I can't find any documentation about it The ones I'm looking for are: Minimum bounding geometry (convex hull) Clip a polygon by a ...
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46 views

What is the name of the popular buffer algorithm?

There is a well-known algorithm that I believe is used for the "buffer" function in some GIS libraries and applications. I have a vivid memory of reading the paper that describes the algorithm and ...
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1answer
253 views

Get progression bar into PyQGIS 3 standalone script

When I run a treatment inside QGIS with Processing toolbox (native algorithms) I get a progression bar : Is there a way to use this percentage inside a standalone PyQGIS script? I searched in the ...
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Creating decision rules on pixel level in time series layer in R? [closed]

I am using Landsat 5, 7, 8 images and RStudio. My goal is to compute the disturbance in a given area using the Vegetation Change Tracker (VCT) algorithm. I would like to ask you if you could provide ...
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1answer
558 views

Run pyQGIS algorithm on selected features in layer

I try to run algorithms on layers but only on selected features with QgsProcessingFeatureSourceDefinition in a loop and then write the result with QgsVectorFileWriter : layer1 = QgsVectorLayer(path1, ...
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1answer
287 views

PyQGIS processing: Overwrite not possible

I have a QGIS plugin that runs the v.clean algorithm two times (first time snap, second break) on a chosen layer: output = self.dlg.directory.text() params_snap = { 'input' : input, ...
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1answer
224 views

PyQGIS Processing: “memory: not found”

I try to run a QGIS plugin in QGIS 3.4 that uses processing to execute algorithms in a row: params_snap = { 'input' : input, 'type' : 1, 'tool' : 1, 'threshold' : ...
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1answer
137 views

Using Google Encoded Polyline Algorithm Format with Oracle Database

Google's Encoded Polyline Algorithm Format is implemented in several GI tools. PostGIS e.g. has ST_AsEncodedPolyline and ST_LineFromEncodedPolyline functions. In contrast, Oracle Database has no ...
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1answer
394 views

How to get equidistant points from a linestring (geographical coordinates) [closed]

I want to resample geographical coordinates based on a specific number of values, let's say, 1663 for the following case: -78.0599088 -11.89402416 -78.04317744 -11.88622134 -78.0267798 -11.87700462 -...
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1answer
341 views

How to combine geometries and numbers in Google Earth Engine

Trying to combine coordinates (geometries) with their respective slope (numbers) in Earth Engine. I am quite lost as to how to go about doing this. I've tried using ee.Algoritm.Feature to add metadata ...
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75 views

Calculating closest distance from location to given route?

I want to calculate the closest distance from a location (lat/lon) to a given route. The route consists of approximately 20.000 location points. I could calculate the distance to every location point ...

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