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
7
votes
2answers
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 ...
6
votes
0answers
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 ...
6
votes
0answers
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 ...
6
votes
0answers
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 ...
4
votes
0answers
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 ...
4
votes
0answers
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 ...
3
votes
0answers
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 ...
3
votes
1answer
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 ...
3
votes
0answers
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 ...
3
votes
0answers
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). ...
3
votes
0answers
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- ...
3
votes
0answers
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. ...
3
votes
0answers
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? ...
3
votes
0answers
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'...
2
votes
0answers
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 ...
2
votes
0answers
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 ...
2
votes
0answers
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 ...
2
votes
0answers
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 |...
2
votes
0answers
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. ...
2
votes
0answers
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 ...
2
votes
0answers
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 ...
2
votes
1answer
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 ...
2
votes
0answers
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 ...
2
votes
0answers
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. ...
2
votes
0answers
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 ...
2
votes
0answers
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%....
2
votes
0answers
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 ...
2
votes
0answers
159 views

Finding adjacent MGRS blocks/grids?

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 ...
2
votes
0answers
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 ...
2
votes
0answers
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 ...
2
votes
0answers
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 ...
2
votes
0answers
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 ...
2
votes
0answers
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)= [...
2
votes
0answers
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 ...
2
votes
0answers
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 ...
2
votes
0answers
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 ...
2
votes
0answers
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 ...
2
votes
0answers
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 ...
2
votes
0answers
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 ...
2
votes
0answers
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.
1
vote
0answers
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 ...
1
vote
0answers
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 ...
1
vote
0answers
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....
1
vote
0answers
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 ...
1
vote
0answers
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/...
1
vote
0answers
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 ...
1
vote
0answers
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 ...
1
vote
0answers
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 ...
1
vote
0answers
49 views

Choose between 2 algorithms in my script

I would like to know how can user chooses between 2 algorithm's parts in my script. User must be able to chose between 2 methods to integrate a variable : automatically with a character selection in ...
1
vote
0answers
132 views

How to calculate if a turn is required from a set of coordinates?

I have some polyline data that represents a navigation route generated using Dijkstra's algorithm. Along this route I would like to calculate anytime a turn is required. Ideally, this would be some ...