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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35 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
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2answers
62 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 ...
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50 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 ...
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0answers
34 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)= ...
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66 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 ...
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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 ...
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1answer
34 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 ...
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1answer
43 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 ...
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0answers
26 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 ...
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2answers
85 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
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1answer
26 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 ...
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141 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 ...
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1answer
96 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) ...
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56 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 ...
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1answer
117 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
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1answer
126 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 ...
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22 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 ...
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4answers
234 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 ...
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1answer
90 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 ...
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4answers
430 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?
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1answer
30 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 , ...
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2answers
115 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.
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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). ...
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29 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, ...
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1answer
36 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 ...
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1answer
89 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
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1answer
50 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 ...
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0answers
91 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, ...
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45 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
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1answer
78 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 ...
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2answers
225 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 ...
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3answers
311 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 ...
2
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0answers
120 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? ...
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1answer
64 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 ...
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0answers
77 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 ...
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1answer
46 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 ...
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0answers
43 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 ...
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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 ...
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1answer
112 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
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1answer
86 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
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1answer
50 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
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2answers
243 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 ...
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0answers
109 views

Available modules/products for GPS+IMU sensors shipped with sensor fusion SW?

Are there any solutions/products (modules) in the market that integrate GPS and IMU sensors that come together with the sensor fusion algorithms (Kalman filtering etc.) implemented and ready for use? ...
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0answers
167 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 ...
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48 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
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1answer
126 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), ...
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17 views

Getting incorrect results for Geary's Coefficient algorithm (incorrect math?)

I'm not sure if anyone here can help me with this, but I'm currently working on a program that uses a spatial autocorrelation algorithm to analyze patterns in an image. It's supposed to return values ...
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0answers
34 views

How can I automatically make new computings after I have modified some value in a field in ArcGIS Desktop?

I'm a computer programmer and I have no idea about geographic things. I have got a long algorithm with a lot of computings, computed from a previous computed field. There are 7-8 computed fields and ...
2
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1answer
96 views

J2000 to WGS84 in QGIS?

How to transform Earth-Centered Inertial J2000 CRS to WGS84 CRS in QGIS? I searched J2000 in spatialreference.org, however nothing found. I don't know the proj4 string of J2000. Any advice would be ...
2
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2answers
137 views

Is there an algorithm for transforming from CGCS2000 to WGS84?

Is there an algorithm that supports transforming from CGCS2000 coordinate to WGS84 coordinate? CGCS2000 is China Geodetic Coordinate System 2000. Any advice would be thankful!