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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2
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2answers
56 views

Routing algorithm for geographical data

I have a graph extracted from an American city: vertices represent road intersections, edges/arcs represent road segments connecting the intersections. For each road segment, I have the length and ...
1
vote
0answers
39 views

Looking for a data set of geo tracking for a group of users

I run a study on user commuting patterns and I need a data set where each line would be something like: userID | Timestamp | lat | long Then, I would like to analyze each user separately and derive ...
5
votes
1answer
73 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 ...
3
votes
2answers
62 views

Construct curve of equal distance from two straight lines

Given two straight lines defined by two points each, I want to get the line which separates points nearer to line a from points nearer to line b. The attached PostGIS code is an example case, it finds ...
1
vote
0answers
32 views

Make “qgis:delaunaytriangulation” and “qgis:dissolve” save their outputs on a specific predefined layer

I'm new to python and QGIS. I'm working on modifying a plugin which runs algorithms "qgis:delaunaytriangulation" and "qgis:dissolve" like so delone_triangles = ...
0
votes
1answer
39 views

ST_Dwithin Source Code

I am looking for the st_dwithin postgis source code. I want to learn the way postgis determines whether a given geometry is within a given radius to another geometry.
9
votes
2answers
75 views

Fuzzy least-coarse common partition algorithm

Given two different partitions of a shape (for argument's sake, two different administrative divisions of a country), how can I find a new partition into which both of those partitions fit, allowing ...
6
votes
0answers
67 views

How to minimise number of dynamic pages to map scattered point

From time to time I have to produce mapbook to show points of interest. First step to create pages, using regular mesh: I don't like the solution because a) there are some pages with single points ...
2
votes
0answers
39 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)= ...
3
votes
0answers
114 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 ...
0
votes
0answers
14 views

ArcByCenterPoint - coordinates of start/end points [duplicate]

Given an ArcByCenterPoint, defined by: center position (lat,lon in WGS84) radius (meters) startAngle (degrees) endAngle (degrees) how can we compute the position (lat, lon) of start/end ...
1
vote
1answer
37 views

Exporting output in ASCII from a QGIS model

I'm trying to find a geoalgorithm in QGIS's Graphical Modeler that can convert and export a vector to ASCII. Could anyone enlighten me if there's an option for that? Perhaps through some script but I ...
0
votes
1answer
52 views

Simultaneous multiple vector layer intersection algorithm

Is there an algorithm, you can suggest or recommend, that I can implement to intersect multiple vector layers? I have a few hundred layers I want to intersect and thinking of developing a little QGIS ...
0
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0answers
27 views

algorithm of v.rectify, v.transform for georeference

Please can anyone tell me what algorithm is used in v.rectify and v.transform to georeference in Grass Gis. Binh grass.osgeo.org/grass70/manuals/addons/v.ply.rectify.html ...
2
votes
2answers
113 views

A method for noise reduction in GPS derived cycling routes

I'm pre-processing GPS data to assess possible methods for a planned research. The aim of the research is to use crowd-sourced cycling routes data to plan a cycling paths in an Israeli city. ...
2
votes
1answer
32 views

Algorithm to remove Loops from a Line-String

I am using a third-party API to acquire a linestring representing a route. Occasionally, this API (which I will not name, here) returns a linestring that contains loops. Logically, this makes no ...
2
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0answers
192 views

open-source code for the map matching algorithm

For map matching of the GPS data to the network data, there is a algorithm from Schussler, N. & Axhausen, K. (2009a). Is this algorithm released under open-source license ? Where can I find this ...
1
vote
1answer
107 views

Algorithm to detect entity (aircraft, ship, etc) intrusion into geographic area

I have been tasked with coming up with an algorithm to determine whether or not an entity (aircraft, ship, etc) is inside or outside of a geographic area defined as a set of geodetic (lat/long) ...
0
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0answers
67 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 ...
4
votes
1answer
128 views

Does this ArcGIS flow accumulation example have an error?

The lower right corner of the flow accumulation example in ArcGIS Desktop's documentation has a flow accumulation value of 2. However, I only see one cell flowing into the lower right corner (the ...
6
votes
1answer
144 views

Project location on a (great circle) path

I've been searching this SE site for quite a few hours now, and I'm still struggling to find a solution to my question. My goal is that given a way in OSM and my location (lat/lon coordinates), I want ...
0
votes
0answers
24 views

Band values after TOA reflectance calibration of WV-2 exceed 1

I use custom python-GDAL script to calibrate WV-2 scenes to TOA reflectance accordingly to 'Radiometric_Use_of_WorldView-2_Imagery'. Here you are a histogram example with the pixel values of the ...
0
votes
4answers
350 views

Fix Self Intersecting Polygons Manually

I are looking to implement a method to fix self-intersecting polygons by editing the vertex order. We want to take the polygon rings and re-arrange/add in vertices to make a valid polygon. This is ...
1
vote
1answer
109 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 ...
17
votes
4answers
469 views

Finding the Center Line from a set of 3D Points

I have a set of 3D points. They follow a curved pattern with a rather constant diameter as shown below. What would be the algorithm to trace the approximate center line of these points?
0
votes
1answer
31 views

Geoserver labeling algorithm

Hello everyone (good morning, afternoon and evening ) :) im really interesting in knowing what kind of algorithm does the Geoserver use when presenting its maps. The Geoserver has its own algorithm , ...
0
votes
2answers
128 views

How to calculate a set of minimum bounding boxes for a polygon

I need to calculate a set of minimum bounding boxes for a polygon. Id est having a complex polygon I want to envelope it with a set of small boxes instead of a big one.
1
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0answers
34 views

Calculate an intersection point of multiple spheres on the surface of earth [duplicate]

The question i am going to ask is very much similar to this question-How to calculate the intersection of 2 Circles? But the problem here is, the radius of the spheres are too small (within 8 meter). ...
0
votes
0answers
30 views

automatic extraction of dtm using grass gis

i have generated dsm using erdas lps tool which is in img format. i want to import this file in grass gis and extract dtm. can you please tell me how to input the data , in which format it should be, ...
1
vote
1answer
40 views

Assign points with varying radii to central meeting locations

I have a set of points in a city, each with a maximum distance radius of 0.5 - 1.5 miles. From this set of points, I'd like to create a small number of 'meeting points', i.e. locations that are ...
2
votes
1answer
103 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 ...
2
votes
1answer
56 views

Calculating a point Lat/Lon from another Lat/Lon point angle

I need help for a solution of this problem to make an algorithm: : I have a point O center of a circle of radius r, on this circle there is two point P1 and P2. I know latitude and longitude of ...
2
votes
0answers
99 views

ArcGIS - Flow Direction (Algorithm)

I am curious about the algorithm of Flow Direction in ArcGIS. Recently I am studying about Hidrology, and I have some questions regard to Flow Direction in GIS. The size of this cell is 100m x 100m, ...
0
votes
0answers
54 views

Recommendations for route optimization algorithms to handle more variables than just distance

I'm researching route optimization algorithms for my graduate supervisor. He'd like an algorithm to optimize routes for the local library's "library-mobile" that will travel to various neighborhoods. ...
2
votes
1answer
90 views

How to programmatically partition a large Polygon in smaller parts within a given Area Threshold?

I'm looking for a Java library, or even an algorithm to do the following: I have a large polygon, about the size of a large city. I need to break it down into smaller polygons such that: The area ...
1
vote
2answers
250 views

How to calculate the Oriented Bounding Box (OBB) of a polygon or point set?

I'd like to calculate the "Oriented Bounding Box" (OBB) which is the enclosing rectangle aligned to the longest extent of a point set (which is not necessarily aligned with the axes of the co-ordinate ...
1
vote
3answers
385 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 ...
3
votes
0answers
122 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? ...
1
vote
1answer
66 views

Geoserver (automatic labeling generalization)

I am a Master student looking to do my thesis in cartographic labelling using GeoServer. The thesis topic will be something like "Cartographic Labelling in Real Time Mapping using Web Services. I am ...
0
votes
0answers
86 views

Where to find more detail on algorithms used in ArcGIS Desktop's location allocation solver?

Where can I find more detail on the algorithms used in ArcGIS Desktop 10.0's location allocation solver? The help file specifies the following: The location-allocation solver starts by generating ...
1
vote
1answer
49 views

Determine when heading off course

How does google or other map providers with routing capabilities determine when you are not staying at the right course? I am trying to figure out how to implement this feature in my gps that I am ...
0
votes
0answers
47 views

Algorithm to scan a road network geometry using directions service

Let's suppose there's a Directions Service which, given a pair of points, returns the geometry, along the network, which best connects those points (which are previously projected - "snapped" - to the ...
0
votes
0answers
19 views

Is there a Minimum Cut Network Delineation Package in QGIS?

Currently I am working out how to best subdivide a pipe network into respective areas. One of the best ways to delineate this network is to subdivide the region into strongly connected areas such that ...
1
vote
1answer
119 views

Cover a polygon with fixed size squares

Can you please advice me of an algorithm (which I can implement in a Java) to cover some polygon (not exact cover) with squares of certain size (aXa squares)? The cover doesn't have to be exact - ...
2
votes
1answer
89 views

How to find if two gps tracks were from the same trip?

Given I have gps tracks from many users running or hiking, how can I find out who were running together? In other words, which algorithms are there to find out who were in the same party? Haven't ...
2
votes
1answer
51 views

Is this Intersect or Union algorithm associative?

Similar to Is the Intersection Operation Commutative? . Spoiler for that one: Intersection is commutative and associative. I've created an algorithm (in PostGIS but the theory would work in other ...
5
votes
2answers
264 views

Best flow routing algorithm for determining location where spill enters stream?

What would be the best flow routing algorithm for determining the quickest (and by this I suppose I mean shortest) path that a spill would take when traveling to a stream? My best educated guess ...
1
vote
0answers
188 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 ...
0
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0answers
53 views

A Distributed Cost-Distance Algorithm

I'm currently trying to implement a distributed cost-distance algorithm, however I can't seem to invent my own and still make it fast. I've been googling around a bit but haven't found anything that ...
2
votes
1answer
138 views

Using netCDF4 Python climate algorithm?

I have been working in Python with the Acaconda Python distribution to create code that accomplishes the following algorithm: I have multiple variable netCDF4 files [NCEP Reanalysis tmax(K), tmin(K), ...