A mathematical procedure used to solve problems with a series of steps. Algorithms are usually encoded as a sequence of computer commands.

learn more… | top users | synonyms (1)

3
votes
1answer
164 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 ...
-1
votes
1answer
34 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 ...
3
votes
0answers
42 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 ...
0
votes
0answers
32 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 ...
4
votes
2answers
151 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 ...
3
votes
1answer
41 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 ...
0
votes
0answers
25 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) ...
1
vote
2answers
38 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 ...
1
vote
0answers
60 views

Explaining different results from Ordinary Kriging and Universal Kriging?

When using either methods to create a surface from the same set of observations, these surfaces differ from each other. Visually it can be seen in the differences of the following contours ...
2
votes
0answers
53 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 ...
1
vote
1answer
54 views

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 ...
1
vote
1answer
47 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 ...
1
vote
1answer
30 views

Algorithm to realize monotone polyline?

I'm searching about the algorithm helping me realize monotone polyline. I would wonder if anyone has any program realizing monotone polyline.
0
votes
0answers
35 views

Geological map generalization polygon aggregation

I am working on generalization of Geological maps and the first thing I am wondering about is aggregation of separate patches that may have same class and which are closely situated to each other. ...
5
votes
1answer
104 views

Travel planning - Finding farthest points of a polygon

I’d like to organize a tour around the lake with 2 objectives: maximise the length of shores to view minimise travel distance In order to do so I can: Pick 2 most remote points on the lake in ...
1
vote
0answers
23 views

Convert moving duration into routes

Which algorithm, that is based on open Street map takes the current GPS position, a duration and an average speed or way of transport(by foot, by bike or by car) and outputs possible routes, that ...
1
vote
0answers
22 views

Create a center node based on both polygon and line shapefile

Sorry for cross posting. I want to develop a node layer from two other layers. One of the layers is a polygon contains a series of zones. Another layer is a line layer of roads. The nodes I want to ...
1
vote
1answer
83 views

Geofencing Issue (Leave/Enter geofence Timing Issue)

I already search SE already if the question has been raised before but I can't find one so I'll ask here anyway. I'm creating a small application which involve geofencing my GPS device doesn't have a ...
0
votes
0answers
26 views

How to find the most accurate street/road by a given coordinate and some previous locations?

I'm building an application that gets user's position and tracks its changes while driving providing some information stored in shape file. To get the most accurate information from this shape file ...
0
votes
0answers
91 views

Calculating intersection between lines with GeoTools (java)

I have ArratList<Segment> (N segments - array size is N) when: public class Segment { Node vertex_1; Node vertex_2; } public class Node { double latitude; double longitude; } ...
0
votes
0answers
39 views

Code implementations for Isovist, visibility [not build in tools in ArcGIS]

I'm looking for things similar to this: http://www.visilibity.org/ This is Open Source C++ library for Isovist & visibility computations. Similar code exist for example inside ArcGis and other ...
2
votes
2answers
97 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 ...
5
votes
1answer
367 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
79 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
48 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
78 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
85 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 ...
9
votes
2answers
136 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
57 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
348 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
15 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
42 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
82 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
votes
0answers
51 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
243 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
53 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
votes
0answers
432 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
145 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) ...
1
vote
0answers
98 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
181 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
215 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 ...
3
votes
1answer
187 views

How to find the concave hull for a cloud of points in 3D space?

The existing algorithm for convex hull is not able to capture the feature for a set of 3D points. Moreover, I found few mathematic tools have this function to obtain the concave hull and their ...
0
votes
0answers
41 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
976 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
232 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
696 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
32 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
189 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
vote
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
39 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, ...