# 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.

87 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
4k views

### C# implementation of concave hull / alpha shapes

I'm looking for a C# implementation of the Concave hull (alpha shapes) algorithm. I already found several Java, Python and C++ implementation but no C# version. The other implementation are quite ...
220 views

### Packing squares polygons in a raster grid

In the green area of the raster I have to fit as many square polygons as possible, of three different sizes: 3x3 cell size 2x2 cell size 1x1 cell size With the fact that the approach should be ...
982 views

### library for minimum bounding box “by width” in javascript or python

I'm looking for a library (or at least a code snippet) to calculate the minimum bounding box "by width" in javascript or python. Below is an illustration from the ArcGIS documentation of that ...
728 views

### Translate Orientation from Sensor data to Geo location

I am tracking a device that might loose GPS signal then and there. And when the GPS signal is too low, I should use the accelerometer and Gyroscope sensors data to guess which way they should have ...
116 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 ...
930 views

### QGIS: Release file lock on file used in a processing algorithm at the end of script

I am using runalg (qgis:joinattributesbylocation) on two QgsVectorLayer objects. At the end of my script I'm trying to delete all the files created during the script. I can delete everything except ...
99 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 ...
101 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 ...
45 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 ...
33 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). ...
142 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- ...
150 views

### Optimum Path finding (for Cross Country Movement) using TIN

I am working on path finding algorithm (using A*) for cross country movement (not for road movement) on map using grid based approach. Algorithm supports path calculation considering slope of terrain. ...
263 views

### Is Hershbergers improved Ramer-Douglas-Peucker algorithim worth implementing?

Here is the article with code samples Other than the C code he wrote are their any implementations? Is it worth making a python or R module out of the C code? Are their known flaws to the algorithm? ...
68 views

### Clustering driven by an enum/list

Given a set of 2D points ( or vertices if you want ), the values stored for each point are: coordinate on x coordinate on y an enum or a value from a list in general for the sake of this example let'...
42 views

### 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 ...
45 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 ...
34 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 ...
55 views

### 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 |...
32 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. ...
33 views

### 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 ...
71 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 ...
120 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 ...
101 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 ...
24 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. ...
141 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 ...
137 views

### QGIS processing algortihm crashes in python console but works manualy

I am loading two layers from PostGIS database and I am trying to run 'qgis:intersection' algorithm with them. Execution of the algorithm through the python console initially works but crash after 2-3%....
123 views

### QGIS Projective Transformation Algorithm

I would need to know something more about the algorithm that Qgis (Georeferencer Plugin) uses to georeference with projective algorithm. I have tried to reproduce your results using other software ...
159 views

My requirement is that, say I'm given a MGRS grid (100mX100m), I now need the IDs of all the 8 MGRS grids around the one that was given. One way that is being suggested is as follows. Compute the ...
573 views

### Wrap the set of points to the minimum polygon

Given I have a set of points which represents the circles which are intersected. As result I'm trying to receive the boundary which represent the polygon which wraps all circles. Please take a look ...
2k views

### Algorithm to simplify a Polygon/Series of Points to a given number of Points

I have a polygon (or let's call it just a series of points). I want to simplify it (reduce the amount of points) to a given number of points. Currently I use Douglas Peucker and try to guess the ...
545 views

### Is there an R package for finding the maximum-area rectangle in a non-convex polygon?

Does anyone know if there is an R package out there with an algorithm which finds the largest rectangle within non-convex polygons? I have Googled, searched the R Sig Geo archives, and looked here on ...
64 views

### Creating 30 areas with equal amount of road in irregular polygon using MapInfo?

The result should be something like this just more polygons. Does anyone know about a tool, which given a table, can create a number of polygons which will divide the tables object into, for ...
190 views

### Application of a Piecewise Logistic Function to Extract Seasonality Metrics

I am working with 16-day MODIS EVI (satellite) data and I want to fit a Piecewise Logistic Function through my 23 EVI data values. The following formula is for the Piecewise Logistic Function: y(t)= [...
744 views

### How to check if a polygon contains another polygon in OL3?

Is there any possibility to check if a polygon is contained in another polygon in OL3? I noticed there is a couple of methods in ol.extent e.g. ol.extent.containsExtent(extent1, extent2). But this ...
133 views

### Calculate distance in point collection algorithm

I've got collection of points which are sorted by x,y and distance between n and n+1 (array of objects [{x:0,y:0},{x:1,y:1}....] I would like to calculate distance between all points (point 1 distance ...
109 views

### What graph traversal algorithm should I use?

I would like to write an algorithm which can traverse a graph and hopefully later I can implement it to use for an indoor navigation system. The graph would come from floor plans of a building and the ...
397 views

### Iteration based positioning on Matlab - retrieving coordinates between iterations

This is my first question on SE so let me know if I'm not asking my question in the right place. So basically, I have an algorithm which uses UMTS measurement events for positioning estimation, which ...
310 views

### Placement of a fixed-radius circle on a sphere to maximize point containment

There are many papers on the "Circle Placement Problem" in 2D Euclidean space, but I haven't been able to find any papers discussing this problem on the sphere. The problem is: given a set of points ...
2k views

### Help with Shortest path Algorithm for enormous bus routes database

I am building a bus routes map for Chennai. I use Postgis. In our database we have one table having all the routes along with unique ids given for them. Second table comprises of bus stop names with ...
144 views

### How to reduce trajectories with Bellman algorithm?

I need an algorithm to reduce trajectories with Bellman algorithm. I haven't found anything searching in Google. Can someone help me? It would be cool have it in MATLAB.
16 views

### 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 ...
52 views

### 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 ...
140 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....
79 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 ...
231 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/...
35 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 ...
445 views

### Standard Method to calculate Average Moving Speed from Times & Coords?

...I wasn't sure if this question was best suited to GIS, SO or Math, so after reading GIS Topics I decided to ask here, but I'll relocate if necessary... :-) I'm working on automating various ...
93 views

### Seeking equation/algorithm for angle between straight line and grid north?

I have a cylindrical equidistant projection map containing climate data(equal angle and equal distances). On this projection I have a straight line connecting two latitude and longitude points. How ...