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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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The most optimal map labeling problem algorithm? [on hold]

I'm looking for the most optimal map labeling problem for a set of points in 2D to implement. With the most optimal I mean, that it is shown to perform well when the amount of labels is less than 25,...
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1answer
25 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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37 views

Seeking fastest algorithm to calculate XY centroid of KML LineStrings and Polygons?

I am writing a PHP program that needs to create labels for LineStrings and Polygons in a KML file. Since for whatever reason KML does not support labels for LineStrings and Polygons, I would like to ...
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1answer
40 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
45 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
31 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
38 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
24 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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34 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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1answer
69 views

Seeking QGIS algorithm for Swapping land parcels/plots by property?

I've searched for a QGIS Algorithm for swapping plots in an area by land owners and I didn't find anything. Do you know something that did that? For example, in an area or in a town we have 2 big ...
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2answers
51 views

Listing multiple fields to be dropped at once in QGIS modeler?

I'm trying to drop more than one fields at once in QGIS 3 modeler on Microsoft Windows. I'm using the algorithm "Drop field(s)". What is the good syntax to list multiple fields to be dropped? Not ...
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1answer
42 views

Finding a boundary with a collection of lines and a point

Given a collection of lines and a point how can I discover the closest boundary around the point. In the image below A represents a collection of disconnected lines and B is the boundary I want to ...
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1answer
20 views

Scaling down lat/lon polygon?

I have a set of (lat,lon) coordinates that compose a polygon. Is there a straightforward method to get an analogous set of coordinates defining a smaller version of the polygon? For example, given ...
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0answers
48 views

How can I share with other users a preconfigured algorithm?

I´m creating a process in QGIS, and I make it work automatic. But, I´ve used a preconfigured algorithm in order to avoid selecting shapes every time you use the process. So, is there any way I can ...
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1answer
40 views

Seeking algorithms for DEM generation? [closed]

What are the different algorithms employed for the generation of a Digital elevation model from images captured using an unmanned aerial vehicle ?
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1answer
68 views

Can you auto-populate a field in Survey123 from another field by only pulling certain characters?

I have a field where the user inputs text Aa1Bb2Cc3 Am I able to auto populate another field by only populating the field with Bb or 3. Auto populate the field with characters [4:6] or just [9] ...
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0answers
41 views

Find QGIS algorithm path

According to Using QGIS3 Processing algorithms from standalone PyQGIS scripts (outside of GUI) I try to implement the existing "Split Lines with Lines" algorithm into a QGIS Plugin. To do this I need ...
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1answer
77 views

What algorithm was used for generation of this vector layer?

The second image is a raster layer and in the third image obtained vector layer is so accurate. What algorithm would have been employed? Normal methods doesn't give nearly equal vectorization. I ...
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1answer
107 views

Optimal tiling of polygon using ArcGIS Desktop?

I am trying to tile a polygon with a minimal number of fixed sized squares. Currently I am creating a fishnet over my polygon then spatially joining the squares that intersect the polygon. This is ...
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0answers
67 views

GIS Clustering with drawing predefined square area around points as cluster boundaries

I have a layer of points and I would like to create clusters where a predefined square area of 5km by 5km is the boundary for the cluster. Is there a way to iteratively draw square polygons around ...
3
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2answers
54 views

Can Ksp Algorithm(Shortest Path Algorithm) have a constraint that the suggested paths must include a particular node or link

I am using pgr_ksp algorithm to find out the shortest path between a startnode and endnode by creating a network topology between all the nodes. Pgr_ksp algorithm very well gives me all the shortest ...
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1answer
71 views

Algorithm “qgis:difference” doesn't work in pyQGIS 3

I try to use native algorithm difference of QGIS. But it seams it doesn't work like the others : parameters = {'INPUT': polygons['OUTPUT'], #from temporary layer created before 'OVERLAY'...
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110 views

Debugging Error: Algorithm gdal:dissolve not found in PyQGIS?

I have difficulties with the processing package. I try to run a simple QGIS dissolve in pyQGIS 3. When I run the line : from qgis.core import QgsVectorLayer import processing from processing.core....
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1answer
76 views

Is the Random Trees Classifier in ArcMap 10.5 equal to Random Forest?

Is the Random Trees Classifier in ArcMap 10.5 the same as what is named Random Forest in other applications/software? I see that the parameters are the same and the design seems the same, but I need a ...
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1answer
147 views

Error: Algorithm not found with correct processing use

I try to run a simple dissolve algorithm in a standalone Python 3 script. My code is following : from qgis.core import QgsVectorLayer import processing from processing.core.Processing import ...
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0answers
47 views

Algorithm or library for buffer zone for lat-lon (wgs) coordinates in global scale

Can anyone point to generic algorithm or library for buffer zones if the source data is in WGS84 degrees? The buffer width should be in meters, as buffer in degrees it generally does not make much ...
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75 views

Formula to calculate DGPS correction factors

I am trying to implement a differential GPS algorithm. During my research, I found a paper at https://opus.bibliothek.uni-wuerzburg.de/opus4-wuerzburg/frontdoor/deliver/index/docId/11361/file/...
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2answers
1k views

Creating buffer circle x kilometers from point using Python?

I am wanting to create a circle with an inputted radius around a point of predetermined latitude and longitude. I've been trying to use the formula found in this post which uses an algorithm ...
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0answers
35 views

Determining average local azimuth of stream channel?

I am working with some LiDAR based DEMs to examine stream channel and riparian morphology. I want to determine, given a point in a stream, the average azimuth that the stream is heading within a ...
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0answers
42 views

Error message with the v.to.3d algorithm on MacOS Sierra 10.12.6

I am very new to QGIS and Im having trouble running the v.to.3d algorithm as I get the error message below. Traceback (most recent call last): File /Applications/QGIS3.app/Contents/MacOS/../Resources/...
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0answers
20 views

Dividing space into homogeneous connected areas [duplicate]

Is there an algorithm (or software) for splitting a map into K connected areas such that the within-area variance of some variable is minimised, and the between-area variance of that variable is ...
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1answer
44 views

Remove small interstices on the edges of a polygone

How can I remove the white interstices on the edges (and interior) of a polygone or polyline, as represented in the first figure below? I want to get smooth and continuous edges, capturing the global ...
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0answers
18 views

How to take all active layers as input for an iterative algorithm?

I have a whole list of different layers I want to do a iterative clipping algorithm on. (Batch processing is not an option as the 'iterate' button is gone.) This is a follow up on my question here. ...
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0answers
81 views

Speed execution of PyQGIS algorithms

I don't understand why if I do "manually" some algorithms I get results much faster than when I insert the same in a pyqgis code (with the same input). This happens, for example, with the extract ...
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1answer
37 views

Problem with number entry QGIS modeler

i created some number entry in QGIS modeler I created them specifically for them to be decimal numbers and not integer. But when i try my model, when i put a decimal number like 0.255 the value ...
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0answers
32 views

How does iterative clip decide its processing order?

I have a fishnet grid which I use to iteratively clip several large shapefiles. The output of the clipping tool results in the selected output filename plus an incrementing suffix (_0, _1, _2 ... _n). ...
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1answer
102 views

How to link Number value with Field calculator in QGIS Modeler ?

I want to link 2 number values (RMSE & dosemax) in a field calculator formula. When I run the modeler, I add these values but it doesn't recognize them. I dont want to create a new table. Just use ...
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19 views

Understanding the problem of applying A* on a multilevel network

I am currently working on an indoor routing project for a multilevel building.For this, I want to find a shortest path over multiple level (or 'floors'). I have read some papers on A* in such an ...
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50 views

Yen's or Eppstein for path with intermediate destinations which are dangling nodes

I'm trying to find a shortest path algorithm (which does not need to be optimal) for a path with intermediate destinations. Consider the following case: One wants to go from A to Z and in between ...
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0answers
114 views

Convert Raster to grid [duplicate]

I want to convert or a raster into a grid. I am with QGIS. I have a raster of a parcel. I have a vector grid of the same area. I want to add in each block of the grid a mean value of the raster. ...
2
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1answer
244 views

How to memorize temporary layer from processing.runalg() in pyqgis?

I created some geoalgorithms with QGis and I need to use them in a Python script. By saving the layer obtained in a file having a specific path, I do not have problems. For example: processing.runalg(...
2
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1answer
240 views

Let QGIS 3.0 Processing algorithm output a VectorLayer loaded via the delimited text provider

Following up on this question, I need to be able to setup the QgsVectorLayer loaded via the delimitedtext provider as my algorithm output. Note that I am still working from this template. For lack ...
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0answers
30 views

How to Make automatic classes with algorithm in qgis modeler?

I have 1 column of numeric data in one attribute table of a layer made of points. I want to regroup this data in classes (style) with the Qgis modeler and each class must have a specific lenght that ...
2
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1answer
72 views

Piping custom processing algorithm output into another in QGIS?

I am using QGIS 3.0. Following up on Calling a QgsProcessingAlgorithm from a Processing python script in QGIS 3.0?, I am writing a Processing python script based on the template provided here. It ...
2
votes
1answer
467 views

Calling a QgsProcessingAlgorithm from a Processing python script in QGIS 3.0?

I am writing a Processing python script based on the template provided here. I am creating lines (destined to the 'OUTPUT') and I would like to clip them according to a polygon entered as the '...
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0answers
222 views

how do I enter start point in shortest path algorithm in QGIS 3.0.1?

Are the x and y values displayed by the Vertex Editor (bottom left of image) not the same as the x and y values in my TestNetwork layer required by the Shortest path algorithm?
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0answers
91 views

Seeking algorithm behind End Point Rate (EPR) to calculate movement of shoreline over period of years?

I am analyzing the shoreline change over a period of 20 years(1998-2018). I have following data: digitized shorelines of 1998, 2003,2008,2013 and 2018 one common baseline for all shorelines transect ...
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0answers
73 views

need Matching Algorithm which takes graph Topology into account

Problem: I have a problem (illustrated below) with matching two datasets. On the left I have a GIS containing drain network data (in blue), including diameter, length and topology information (from- ...
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1answer
113 views

Setting GroundFilter parameters for low density point clouds?

I'd like to use the function GroundFilter on my dataset. However, the manual says that the default values of the parameters used by this function (g parameter, w parameter) are related to a high ...
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1answer
264 views

Given a lat/long find all points within a certain radius

I am looking to find multiple lat/long points (N,S,E,W) that are 100 metres from an input lat/lon point I have stored in PostGIS. So, given a latitude and longitude I'd like to find the latitude and ...