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
152 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 ...
2
votes
1answer
163 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 ...
-1
votes
1answer
33 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 ...
1
vote
1answer
263 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 ...
1
vote
1answer
46 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 ...
3
votes
0answers
41 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 ...
1
vote
3answers
856 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 ...
1
vote
1answer
221 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 ...
8
votes
2answers
1k 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 ...
4
votes
2answers
150 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 ...
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 ...
31
votes
13answers
12k 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 ...
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 ...
39
votes
6answers
19k 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) ...
5
votes
1answer
350 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 ...
0
votes
0answers
22 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) ...
7
votes
1answer
199 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: ...
1
vote
2answers
36 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
1answer
51 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
0answers
57 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 ...
9
votes
3answers
179 views

Understanding location storage and query algorithms?

One of the most important aspects of a GIS-equipped database is that it provides the user with the capability to quickly query for all points within some arbitrary geographic area that match some ...
7
votes
4answers
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 ...
17
votes
7answers
29k views

Calculating Lat/Lng X miles from point

I am wanting to find a latitude and longitude point given a bearing, a distance, and a starting latitude and longitude. This appears to be the opposite of this question (Distance between lat/long ...
6
votes
6answers
2k views

Finding shortest path while avoiding polygon features

I'm developing an extension to ArcMap where I have a set of static, concave polygon features and I'm trying to find the shortest path between 2 points without crossing any of the polygons. Is there ...
9
votes
2answers
135 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 ...
81
votes
13answers
26k 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 ...
3
votes
1answer
179 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 ...
6
votes
1answer
984 views

Explaining different Standard Deviation results from same data in ArcGIS Desktop and MS Excel?

I have done some interpolation in Geostatistical Analyst in ArcGIS and I got the Standard Deviation (SD) a bit different from the SD that I calculated in Excel Spreadsheet. What algorithm does each ...
2
votes
2answers
278 views

How to discretise a line into grid lines

Having a line and a grid, the aim is to discretise the line into grid lines. In the following figure, the given line is in black, its intersections with grid lines are blue, the desired is set of ...
5
votes
1answer
6k views

Calculating Topographic Wetness Index (choosing from different algorithms)

Topographic Wetness Index can be expressed as Ln(a/tanB) based on the idea of Beven and Kirkby (1979) where a is the spesific catchment area (a=A/L, catchment area (A)divided by contour ...
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. ...
4
votes
3answers
2k views

Similarity between two raster maps

Having two raster maps as the examples below: We are interested in evaluating their similarities. As shown, they are not fully overlapping. We guess one way is to clip small one area from the ...
7
votes
1answer
587 views

Calculating bearing of building using ArcGIS Desktop?

Is it possible to get the main bearing of buildings by floor plan? I want to have a building (by ID) and it's main bearing (e.g. E/90° or W/270°). The idea is to change the polygon-feature class into ...
6
votes
0answers
373 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
1answer
199 views

Which spatial bundling or grouping algorithm optimally groups elements by attribute?

As I delve deeper into GIS, I find myself trying to improve efficiencies of certain procedures and processes. The one process I'm working on now is spatially scheduling construction projects. For ...
11
votes
2answers
2k views

Drawing Day and Night on a Google Map

I'm looking to plot day/night on a Google map, for an arbitrary point in time. I'm familiar with generating map tiles; I'm just looking for an algorithm to tell me whether a particular point on the ...
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 ...
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
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 ...
3
votes
5answers
864 views

Counting overlapping polygons in GeoJSON to result in new set of polygons?

I have 100 polygons in a GeoJSON file that partially overlap each other. I would like to produce 100 new polygons as follows: The area covered by any of the original 100. This is their union. The ...
1
vote
1answer
77 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
86 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
36 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 ...
1
vote
0answers
56 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 ...
2
votes
1answer
375 views

Implementing genetic algorithm in ArcGIS Desktop? [closed]

I want to implement genetic algorithm to find optimum location for placement problem with ArcGIS. Can any body explain it (step by step ) or any resources about that?
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 ...