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)

6
votes
2answers
397 views

how to find the point in a country furthest from a boundary

i'm trying to find the point in south africa furthest from the sea or a landward boundary. my method thus far: i obtained a first guess at the centre of the inscribed circle and the three segments ...
4
votes
2answers
6k views

Calculate bearing between two decimal GPS coordinates

I'm building a virtual tour application that uses custom panoramas in conjunction with Google's StreetView service. With StreetView, you can have 1 to n links at each particular location to move to, ...
8
votes
1answer
1k views

Computational most efficient way to convert Cartesian to Geodetic Coordinates

As far as I understand the literature there are several ways to convert a set of geoecentric cartesian coordinates to geodetic coordinates Bowring, 1976 Borkowski, 1989 Lin & Wang, 1995 Toms, ...
6
votes
1answer
406 views

How to calculate the bearing of a building (ArcGIS)

How 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 ...
11
votes
4answers
563 views

Dikes extraction from DEM

I do have DEM of 1x1 meter and original LiDAR point cloud in .las, that DEM is made of. I need to extract river dikes (highest points of the dikes) to vector feature (point, polyline). Any idea for ...
1
vote
1answer
108 views

Algorithm to find distance of an uneven polygonal road

While working for my summer internship I have got a task to implement an algorithm to find the crosssecting points of two roads or more and then place that cross-section point a number and then find ...
3
votes
2answers
1k views

How to find a point on given line that its distance from another point is given also?

I have this input: (lat1,lon1), (lat2,lon2) - Two coordinates that create the line (lat0, lat0) - Point on this line d - distance I want to find a point (lat, lon), where (lat, lon) is on the ...
2
votes
3answers
282 views

Get the LatLon of middle points of a road segment?

Suppose I have the LatLon of the two end points as well as a small number of middle points of a road segment. What is the best way to calculate the LatLon of a middle point P of the road segment ...
6
votes
1answer
971 views

Grouping map points into fixed cluster sizes

I have a dataset of 655 lat/long pairs which I'd like to split into about 100 groups. A group should have 5-10 pairs which are geographically close to each other. Dense groups should have more ...
3
votes
1answer
533 views

Why are the results from the same data different in ArcGIS vs 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
3answers
563 views

Split polygon with holes to get several hole-less polygons

Unlike this thread I actually need to split the polygons into several hole-less polygons. I'm not sure on how to approach to this problem. I have polygons with holes of many diferent shapes, like ...
6
votes
3answers
4k views

Splitting lines automatically at specific distances using ArcGIS Desktop?

I have a set of polylines which I need to split at varying distances from their starting points. In general, I'm looking for a something similar to the SPLIT function within the editor tool. There ...
5
votes
2answers
264 views

Raster calculation confusion

I need to do some raster calculation, I've been trying to make it work but I am not sure everything is working properly. I need to apply a formula, but I am unsure if I am doing it properly. The ...
16
votes
1answer
1k views

Robust alternatives to Moran's I

Moran’s I, a measure of spatial autocorrelation, is not a particularly robust statistic (it can be sensitive to skewed distributions of the spatial data attributes). What are some more robust ...
2
votes
0answers
61 views

Computational time of well-known compression algorithm [closed]

I have googled for get information about computational time of some compression algorithms but information seems contradict each other. I need worst case performance of the following algorithm Sliding ...
9
votes
1answer
248 views

Looking for a trajectory similarity measure

For my final academic work I have developed a compression algorithm for GPS trajectories. I can estimate the quality of the spatio-temporal compression by computing the syncronized euclidean distance ...
2
votes
0answers
76 views

How to reduce trajectories with Bellman algorithm?

I need an algorithm to reduce trajectories with Bellman algorithm. I haven't found anything searching in Google. Can someone help me? It would be cool have it in MATLAB. Thank you
2
votes
0answers
117 views

Any Open source implementation just like ArcGIS Desktop Identity function? [closed]

I tried to identity thousands of points with millions polygon. ArcInfo work well but i have to get the result from Web Services.So i tried to implement the algorithm(Point in polygon) by myself,it ...
6
votes
1answer
552 views

Breakline detection algorithms for LIDAR dataset

I'm searching for algorithms or open source tools I could use to detect breaklines from a LIDAR dataset; more specifically, from the terrain points of the dataset. At the moment the only thing I've ...
3
votes
0answers
194 views

Pipe Network: Computing the inflows for systems with multiple reservoir (input source)

Let's say, for the sake of simplicity, we have the following Y Shape water pipe network: S1 and S2 are the reservoirs ( input source), Sout is the water demand where water is drawn out for ...
6
votes
1answer
578 views

How do I find least cost path over a DEM based on slope magnitude and direction?

What sort of algorithms can I use to find a least cost path through a DEM where it costs more to traverse a cell going downhill or uphill than it does to follow the contour of the land? All the ...
3
votes
0answers
255 views

How to get all intersections between two simple polygons in O(n+k)? [closed]

Can someone help with a following problem: report all intersections between two simple polygons in O(n+k) where n - is a total number of polygon edges and k - is number of intersections. As a result - ...
27
votes
4answers
6k 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) ...
28
votes
1answer
7k views

How to find the center of geometry of an object?

Well it might be a simple question. Given a set of 2D or 3D points, the question is: How to find the center of geometry of an object? According to the following figure, the center of geometry ...
6
votes
1answer
353 views

How to find the smallest-area ellipse circumscribing a convex polygon?

We are currently dealing with the problem of: How to find an ellipse circumscribing a convex polygon? Recent googling and lots of reading could not help me so much :(
3
votes
1answer
391 views

How Can I Calculate Time from Coordinate?

For my application I am searching for an API or an algorithm for clicking point time and time zone. I dont know how I can do this but after getting time I want to calculate giving coordinate sun ...
5
votes
1answer
214 views

algorithm for displaying holes in a polygon by translating it into several hole-less polygons?

I'd like to plot polygons with holes on a framework that doesn't support holes. The approach to me seems to be to translate the single polygon into several ones adding up to the whole polygon, leaving ...
3
votes
2answers
239 views

Need an explanation on a network simplification algorithm

I try to implement the algorithm described in this paper (page 8), but there's a place that I can't understand, and the authors do not provide a more detailed explanation or pseudocode. They show how ...
3
votes
2answers
867 views

Finding the minimum and maximum distance between an observer and a lat/lon bounding box

I have three points in geographic coordinates (latitude, longitude, altitude). One of the points represents an observer, above the Earth. The other two points define a bounding box. I'd like a ...
2
votes
1answer
2k views

How to get the radius of a “circle” in Openlayers

How do you get the radius of a circle in openlayers? I have searched quite a bit and cannot find any resource for this. please help. Here is my code but I want the radius or circumference of the ...
2
votes
1answer
213 views

Is there any simple Map Labeling Algorithm?

I was looking into how to Label a few features on a small Map, and want to label them on the fly. I would be adding a few features (a maximum of around 6 to 7) as graphics on a web-Map which has ...
3
votes
1answer
816 views

Point of Intersection for a Ray and Earth's Surface

Say I have a ray vector originating from somewhere out in space. An example might be a ray of light from the sun. How can I calculate the point of intersection (if it exists) between the ray and the ...
6
votes
2answers
2k views

What algorithm should I use to remove outliers in trace data?

I have GPX traces and want to remove outlying observations. There are some routepoints that are impossible because it would require acceleration that the vehicle can not achieve. Are there good ...
1
vote
4answers
251 views

Looking for compute intensive GIS vector operations

I am looking to make efficient algorithms for those vector GIS operation that take a long time for GIS software like Arc-GIS, Grass etc. I have considered polygon overlay but looking for other ...
1
vote
1answer
467 views

How to speed up batch watershed delineation?

Hi this is probably a longer-winded question than it needs to be, but please bear with me. I have a large number of pour points - approximately 250,000 for which I want to delineate the upstream ...
7
votes
2answers
223 views

How to handle interpolation of multiple (quality) tiers of irregular data?

I'm going to try to provide a high level overview of the issue - realizing that more details/info will be necessary - but I don't want to write a novel that seems too overwhelming for people to ...
2
votes
2answers
224 views

How to remove roads from dataset

I've got a shape file that I loaded into PostGIS that has both road and parcel multipolygons and I need to remove the roads. I tried loading the shp file in qgis and it loads them both as a single ...
9
votes
2answers
278 views

Custom implementation of ArcGIS function

I would like to find out what it takes to create a custom implementation of an ArcGIS function. In particular, I would like to implement GeoAnalyst.ISurfaceOp2.Visibility() in order to get it to run ...
6
votes
2answers
808 views

How do I select only those features, that are connected?

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 ...
6
votes
4answers
2k views

Point in polygon algorithm for multiple polygons

I've a Google map with bunch of polygons on it. Here is a problem I'm interested in: Given a lat,lng point, what's the best way to determine all the polygons that this point lies in? The obvious way ...
15
votes
5answers
2k views

Algorithm to fix topological errors in GIS software apps

Related question here. I notice that ensuring topological correctness is essential for GIS applications, this is because the input from user or polygon boolean operation can have severe topological ...
11
votes
4answers
413 views

How to generalize coastlines?

I have a large set of data points that essentially represent the coastline of the world. I don't know the exact resolution but I'd say it's in the neighbourhood of 5-10m. Imagine a set of points ...
4
votes
2answers
2k views

Problems using the 'Split' tool with ArcGIS

I'm running into difficulty when using the split tool with ArcGIS 10. I am trying to split lines using a grid that I generated using the Fishnet command. Each gridcell has a unique text value as a ...
5
votes
3answers
1k views

Why doesn't the split tool return any records in the attribute table?

I've been trying to split a large land use shapefile using a set of study area polygons as the split feature, but when the function finally finishes running (the land use dataset is quite large), all ...
5
votes
1answer
978 views

How to create a polygon from other polygon boundaries?

I want to write an algorithm that creates a polygon inside a hole made by a set of other polygons. It's something like a flood fill and it's like the "boundary" tool in Autocad. The image shows an ...
2
votes
1answer
417 views

polygon map overlay algorithm

There are many algorithms for binary map overlay operation in vector data format which take two layers of map and produce resultant layer i.e overlaid layer as output. I am wondering whether there are ...
6
votes
6answers
867 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 ...
7
votes
1answer
196 views

Optimize GEOSGeometry's spatial operations by avoiding thread-safety checks

A ranking algorithm I'm developing for a Django webapp requires performing spatial operations (within, intersections, sym_difference, etc.) using a query against large number of geometry objects. ...
19
votes
3answers
2k views

Meaning of Simplify's tolerance parameter

The standard parameters of Douglas-Peucker's simplify algorithm are geometry and tolerance (e.g ST_Simplify in PostGIS). What's the meaning of the tolerance parameter? I know that the bigger the ...
6
votes
3answers
1k 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 ...