# Tagged Questions

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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### 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 ...
23 views

### data for radius search in shortest path finding?

Is there any way for getting data for radius search ( described here: http://orsnz.org.nz/conf36/papers/Engineer.pdf [ Faramroze Engineer Department of Engineering Science University of Auckland ...
925 views

### Finding projection of point to line?

I have a segment defined by 2 LatLon points(A and B) and a third LatLon point (C). I need an alghorithm, formulae, or some code to find the projection point of C on the segment AB (call this point D) ...
20 views

### Algorithm for converting from projected coordinate system to geographic one using Helmert transformation

I have a data in projected coordinates system and I need to convert them to WGS84. I know the parameters of position vector transformation and I know the projection details of my projected coordinate ...
23 views

### Is it possible to stop an algorithm midway through processing in QGIS?

This question come about do to an annoying though infrequent issue I have been having in QGIS. On occasion, I will begin processing a tool that will take some time to run but realize midway through ...
29 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 ...
228 views

### Segment matching on a polyline

I have about 1000+ running routes which I can load into memory as polylines using latitude and longitude data captured from a running watch. From these polylines I would like to be able to identify ...
71 views

### How to add my own algorithms to ArcGIS toolbox [closed]

I want to implement and test some algorithms for line generalization tool in ArcGIS software by Python programming, but I do not have any access to its tool bar script. My question is, how can I add ...
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### Packing polygons without intersection and empty places [closed]

How can I pack polygons without empty places and intersections? Please tell me everything that might help me (API, algorithms, etc.) I'm using: USPS API to get carrier routes. dbscan.js to ...
258 views

### Generalization algorithms [closed]

Does anyone have the proper codes for line simplification and smoothing algorithms which is good to implement instead of ArcGIS algorithms? For example any of these: Visvalingam–Whyatt ...
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### Optimum Path finding (for Cross Country Movement) using TIN (Triangulated Irregular Network)

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. ...
233 views

### Oil palm stand census algorithm? [closed]

Anyone have experience in oil palm stand census using tree detection algorithm from satellite images in ArcGIS or QGIS? any references for usable algorithm? What is the accuracy?
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### Diagram Ring Elements Locator (Tough Problem)

I asked http://stackoverflow.com/questions/35579843/get-only-ring-nodes-from-a-diagram on stack overflow but there was no help at all. So I hope I get help from someone on here :) I have a diagram ...
33 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 ...
10k views

### Algorithm for finding irrregular polygon centroid (label point)

I need to find a centroid (or label point) for irregularly shaped polygons in Google Maps. I'm showing InfoWindows for parcels and need a place to anchor the the InfoWindow that is guaranteed to be on ...
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### C# selecting map tiles from user defined rectangle points?

I have a WPF user control with which the user can draw a rectangle on the map canvas to define an area for downloading background imagery tiles from a web service. The tiles are in Lat long 1x1 ...
53 views

### Clustering markers using quadtree

I have a POSTGIS database with geography points and i want to cluster the points using quad-tree . I have a map where i have to display the markers clustered or non clustered depending on the zoom ...
42 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 ...
21 views

### Process road polylines to not overlap building polygons

Is anyone aware of a processing tool in Grass or similar which will find segments of polylines which overlap polygons in another dataset and reroute the polyline to avoid the collision? My problem is ...
28k views

### What are Definition, Algorithms and Practical Solutions for Concave Hull?

Convex Hull A convex hull of a shape is defined as: In mathematics, the convex hull or convex envelope for a set of points X in a real vector space V is the minimal convex set containing X ...
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### Given two lat/longs, how can I tell if they are within 1 mile of each other?

I'm trying to implement a very efficient check to see whether two points are within a mile of each other, or not. My current approach is to compute the Haversine distance, and then check to see if ...
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### How to divide line into three equal parts?

I have a problem with line division. I'm writing a program in JS/C++ generating KML files. I was trying to divide a line using my own function (which is correct on cartesian space): var part1Lon ...
24k views

### How to find the minimum-area-rectangle for given points?

The following is another problem that I am working on it these days. As you see in the figure, (BTW, I tried to make it self-presenter) the question is: How to find the minimum-area-rectangle (MAR) ...
30 views

### Algorithm used by location-allocation (Maximize Coverage problem type)

Which algorithm does the location-allocation Maximize Coverage problem type use? I already found on the ArcGIS help that location-allocation uses a vertex substitution heuristic to solve the p-median ...
991 views

### Looking for dissolve algorithm for Javascript

I have three adjacent polygons that together make up a larger shape. I need an algorithm that will dissolve the internal borders leaving only the outside border. An example would be a group of ...
107 views

### Pseudo code to correct Geographic points for UTM Easting distortion on Web Mercator Projection

I have chosen to use a Web Mercator projection system for: Use of Tiling system for low memory usage Accessing only one site/area at a time Reuse of Google Tiles - for many sites In some cases I ...
88 views

### Algorithm for spatial clustering?

I have a series of 2D maps with values ranging 0.0 to 1.0 spread all over. The algorithm that produces them is an application of the fractional Brownian motion. Each map measures 101x101 pixels or ...
106 views

### What would a simple hillshade algorithm be?

I'm curious how GIS systems actually generate a hill-shade from input data like a raster DEM layer. I'd like to implement my own in software (mostly for fun/learning) but I want to start with a ...
2k views

### tiny JS discretization library for choropleth representation

I would like to know if a tiny stat/discretization js library ready to use exists. I do know about the existence of jStat (which I may explore a little bit more thoroughly), and I know that mapfish ...
114 views

### Possible point location algorithm

I need to calculate possible point location based on its speed and some other factors. For example, there is a man in the middle of the forest and I need to calculate his possible location at some ...
494 views

### How to select all files in a directory for merging in Processing?

I'm writing a generic script which involves writing shapefiles to a directory which are then merged together. After writing the files out to the Output folder, I'm trying to get the ...
284 views

### How do I convert a screen position to geographic coordinates?

I'm looking for resources that explain how I should convert screen coordinates (the point that I pick on-screen) to geographic coordinates (lat / lon). I want to build an application where, the ...
233 views

### What algorithm does QGIS use to calculate Nearest Neighbor Index?

I'm carrying out nearest neighbor analysis on a set of geological features in QGIS, trying to find out whether they're clustered or not. I've calculated the nearest neighbor distances using the ...
61 views

### How to check based on GPS coordinates if point is near a given path? [closed]

Path is just a straight line defined by coordinates of the beginning and end of it. My coordinates are simply longitude and latitude of three points: start of the path end of the path my point (for ...
305 views

### Route through water polygons

I have a water-polygon grid shape file as shown (Each grid is 1latx1long): I have created this in QGIS and files (coastal lines and land polygons) selected from http://openstreetmapdata.com/data ...
58 views

### Calculate location on line with known azimuth to point

I have the following situation (consider distances up to 300m - without great circle etc. affects): How can I calculate the unknown location when I have all other locations in the triangle and ...
44 views

### Creating 30 areas with equal amount of road in an irregular polygon

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 ...
1k views

### How to split a line every x meters? [duplicate]

I have a line that I ultimately want to split up into points. The points should be every 100 meter along the line. So I don't want to extract the nodes. Are there any OpenSource (QGIS, Python) tools ...
2k views

### Selecting only canals that are connected to reservoirs?

I have a polygon layer of water reservoirs and a polyline layer of canals. In my data, some canals are originating from reservoirs, and leading to other canals. On the other hand there are some ...
178 views

### Road segments reconstruction from GPS trajectories

We have a 10,000 base of vehicle mounted moving devices which report their GPS position on a time based schedule. All that data is currently being stored in our database for several business related ...
51 views

### GPS coordinates of a point between two known points

I am looking for an algorithm for finding GPS coordinate of a point on a straight line defined by say points p1 and p2 at distance r from p1. GPS coordinate of p1 and p2 are known. I searched a lot on ...
14k views

### Different approaches for map matching : links / ideas?

I'm using Open Street Map and its vectorial road network and I'd like to implement a map matcher algorithm. Currently I'm able, for each GPS position, to retrieve the nearest road segment and ...
47 views

### using a linear solver to get a “centre of gravity” of a set of points

As a programmer, if I have a linear solver available. How can I formulate the following problem as a set of constrains / decisions / goals for the linear solver? I have a matrix of say 10*10, so 100 ...
601 views

### Algorithm to find N nearest points to point

My situation is that i'm trying to build a mobile app, and find the x number of points closest to a users location that satisfy certain conditions that the user chooses on the front end. My current ...
73 views

### Need to find a point a given distance along a linestring

Need to take a linestring and find a coord every x meters along the line. I tried using the SQL Server Spatial Tools and found .NET to be slow and after 5(ish) days of processing, SQL server (or .NET) ...
212 views

### Find and destroy duplicate OSM multipolygon/polygons in TileMill/PostGIS

In OpenStreetMap there are sometimes multipolygons where attributes are present on both the polygon and the multipolygon relation, such as the Grampians National Park: ...
96 views

### How to split osm data

I have a gigantic OSM geodata file of a city, and I want to split it into smaller files according to each group of tags. I googled it up and i found that there is a jar file caller splitter.jar . i ...
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### QGIS crash while delete duplicate geometry

I have a polygon shape with nearly 60 000 features (at around 3 000 square kilometres) in QGIS 2.12. I try to delete duplicate geometries from this layer and the algorithm runs until 99%. Then QGIS ...