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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1answer
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.
2
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1answer
1k views

How to calculate grid convergence (True North to Grid North)?

I would like to know how to calculate the grid convergence angle between True North and Grid North for UTM maps. I am using ArcGIS 10.0 (ArcView licence) and have used the Calculate Grid ...
1
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1answer
160 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 ...
9
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2answers
64 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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0answers
52 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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9answers
20k 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 ...
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1answer
3k views

Create centreline from a polygon

I am working on a project to create a centerline from a polygon automatically. The user select a polygon and click a button, the centerline will create for him. I have tried the build-in function ...
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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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2answers
598 views

How to remove redundant points using Open Source GIS (preferably)?

We have points table including vehicle routes.In huge traffic conditions,devices collecting data on route may output redundant points where at any coordinate same points may repeat.We can easily ...
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5answers
745 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 ...
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0answers
68 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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2answers
2k views

What is the process to calculate Helmert parameters?

I have some double points (the same points in 2 different datums). I'd like to calculate the Helmert parameters but I don't understand how. NOTE: I don't need software. I need an algorithm in order ...
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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 ...
9
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2answers
4k views

How does ArcGIS Desktop calculate INSIDE point for Feature to Point?

Let me back up and say that from what I understand there are two common ways to calculate the centroid of a polygon in ArcGIS Desktop: Using Calculate Geometry on fields within the attribute table ...
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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
696 views

How to speed up batch watershed delineation?

I have a large number of pour points - approximately 250,000 for which I want to delineate the upstream watershed area using ArcHydro's "Batch Watershed Delineation". Given that it takes roughly 4-5 ...
5
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2answers
878 views

Making Buffer like Offset in ArcPy?

I would like to make a buffer for a polyline and get as Output a Polygon with the same angles as the polyline, having not arcs, like in ordinary buffers. i tried the FLAT option in ArcPy, but it's ...
2
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1answer
91 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 ...
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 ...
4
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6answers
3k views

shadow simulation from buildings [duplicate]

is it possible to use hillshade function in ArcMap to calculate shadow areas of buildings or simulate shadows of buildings, using DSM of the buildings and the sun angle and azimuth?
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 ...
2
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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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0answers
144 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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4answers
238 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 ...
2
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1answer
127 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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0answers
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 ...
4
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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 ...
3
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2answers
3k views

How to convert a bing maps quadkey to mercator coordinates

How do you convert a bing maps quad key, such as "03200320023" to coordinates in mercator virtual earth (epsg 3857) coordinate system? I've got an algorithm to convert to coordinates in latitude ...
4
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1answer
1k 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 ...
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0answers
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
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 ...
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1answer
93 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
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4answers
434 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
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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). ...
1
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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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0answers
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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0answers
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. ...
0
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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 ...
2
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1answer
51 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 ...
3
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2answers
119 views

Find gap in / endpoints of linestring

I have a set of features of type linestring. I'm trying to polygonise the linestrings and assumed that they were closed (naive me :) ). Of course some were not closed and I'm trying to locate the gaps ...
0
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1answer
433 views

D8 algorithm to get the flow direction in ArcGIS

I am using ArcGIS 10 for the get the flow direction from DEM. I wonder about the algorithm they have used while calculating flow direction. It is mentioned there that it is using D8 model. D8 model ...
2
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0answers
93 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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2answers
228 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 ...
2
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1answer
80 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
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 ...