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Questions tagged [algorithm]

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
114 views

Using Google Encoded Polyline Algorithm Format with Oracle Database

Google's Encoded Polyline Algorithm Format is implemented in several GI tools. PostGIS e.g. has ST_AsEncodedPolyline and ST_LineFromEncodedPolyline functions. In contrast, Oracle Database has no ...
2
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0answers
35 views

Calculate where a geodesic line crosses a meridian

Given a geodesic line between two points with known coordinates on a sphere, is there an easy way to calculate or approximate where this line crosses a specific meridian? I want to calculate where ...
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2answers
2k 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 ...
4
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3answers
5k 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 ...
2
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1answer
45 views

Perform Tile Index on Newly Created PDFs using PyQGIS

The python code below successfully performs the tile index algorithm on all PDF files stored in sub-folders named !pdf's within my V:Drive. A list of all paths to each PDF exported from QGIS is ...
8
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2answers
209 views

Optimal tiling of polygon using ArcGIS Desktop?

I am trying to tile a polygon with a minimal number of fixed sized squares. Currently I am creating a fishnet over my polygon then spatially joining the squares that intersect the polygon. This is ...
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0answers
15 views

Getting Omniscape analysis ERROR: LinearAlgebra.LAPACKException(3)?

I am currently running landscape connectivity analysis with Omniscape, but I get this error : ERROR: LinearAlgebra.LAPACKException(3) Stacktrace: [1] chklapackerror at /builddir/build/BUILD/julia/...
3
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0answers
33 views

What is the complexity (big / little o) of the ArcGIS watershed delineation algorithm? [closed]

I'm curious about the complexity, in terms of Big or little O notation, of watershed delineation algorithms: More specifically, does the time required to perform a watershed delineation depend on the ...
0
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2answers
206 views

Is the Random Trees Classifier in ArcMap 10.5 equal to Random Forest?

Is the Random Trees Classifier in ArcMap 10.5 the same as what is named Random Forest in other applications/software? I see that the parameters are the same and the design seems the same, but I need a ...
109
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5answers
181k views

Algorithm for offsetting a latitude/longitude by some amount of meters

I'm looking for an algorithm which when given a latitude and longitude pair and a vector translation in meters in Cartesian coordinates (x,y) would give me a new coordinate. Sort of like a reverse ...
0
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3answers
70 views

Splitting Streets to Create Polygons?

I have a need to take all the streets belonging to a certain area (in OpenStreetMap) and split each street by each other and form polygons from the segments that result from the split operation. I do ...
2
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1answer
63 views

How to calculate line complexity index

I'm wondering if there is any suitable algorithm that can I use to calculate line complexity index (or indicator)? By "line complexity" I mean how many bends (direction changes) that line contains and ...
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0answers
19 views

Drawing equal paths from geographic points?

I have 10'000 geographic points (POS), 10 salesmen, and one starting point. To avoid discrimination between salesmen, everyone should travel the same distance and the same number of points of sale. ...
3
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1answer
80 views

PYQGIS 3 Using the ouptut from GRASS v.distance algorithm

I have a script which is trying to run v.distance on two existing shape files, buildings.shp which containing some polygons and singleasn.shp which contains a single point. This will be run from the ...
2
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1answer
92 views

Find QGIS algorithm path

According to Using QGIS3 Processing algorithms from standalone PyQGIS scripts (outside of GUI) I try to implement the existing "Split Lines with Lines" algorithm into a QGIS Plugin. To do this I need ...
1
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1answer
39 views

Calculate position to put box into another container?

there has a big box, and the big box already contains many small box, then should place a new small box into the container. How do I calculate a big enough space to place the small box? There ...
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4answers
3k views

splitting a lines layer using points

I'm looking to accomplish a similar task to this thread: Splitting line at point positions using QGIS? Using QGIS and the Processing and GRASS toolboxes available, I'm looking to split a vector layer ...
0
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1answer
206 views

Debugging Error: Algorithm gdal:dissolve not found in PyQGIS?

I have difficulties with the processing package. I try to run a simple QGIS dissolve in pyQGIS 3. When I run the line : from qgis.core import QgsVectorLayer import processing from processing.core....
44
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13answers
25k views

Map matching links and ideas? [closed]

I'm using OpenStreetMap 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 ...
1
vote
1answer
304 views

Error: Algorithm not found with correct processing use

I try to run a simple dissolve algorithm in a standalone Python 3 script. My code is following : from qgis.core import QgsVectorLayer import processing from processing.core.Processing import ...
6
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2answers
4k 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 ...
72
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7answers
71k views

Finding minimum-area-rectangle for given points?

As you see in the figure, the question is: How to find the minimum-area-rectangle (MAR) fitted on the given points? and a supporting question is: Is there any analytical solution for the ...
9
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1answer
16k 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 specific catchment area (a=A/L, catchment area (A)divided by contour length(...
2
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0answers
33 views

Splitting linestrings based on their curvature

I'm looking for a method to split linestrings based on their curvature, more precisely if part of them could be considered a street corner. For example in the screenshot below, I'd need to split the ...
13
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1answer
267 views

Matching segments of different lengths

I'm trying to match small segments with a larger segment they are the most probably related to: relatively close, similar bearing, and facing each other. Here is a typical example of the data I have: ...
13
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3answers
11k views

Calculating roundness/compactness of polygon?

I am trying to find ways to quantitatively describe the shapes of various polygons. For my project, these polygons represent lakes, rivers, lagoons, and parks. So they can be almost any shape. One ...
5
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3answers
2k views

Finding point in country furthest from boundary? [closed]

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 ...
1
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1answer
55 views

Correlate two different zone system records

I am working with two data sets from different sources that represent the same phenomena and have a challenging point. Both data sets represent demographic attributed of the population [ person id, ...
18
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5answers
45k views

Finding if two polygons Intersect in Python?

I'm looking for an algorithm, a high level solution, or even a library which can help me determine if two polygons intersect, in Python. I have the vertices of the two polygons (These are single part ...
2
votes
1answer
102 views

Adding new attribute field to processing output algorithm in PyQGIS?

I have a processing script that will carry out a selection by expression of the input layer, then do a join attributes by location with a join layer. The next stage will be to add a new field and ...
1
vote
0answers
796 views

Detecting turns of route?

I'm doing a Python simulation of a vehicle, driving along a specified path. I generate dummy GPS readings, that fetch the current position of the vehicle, with some randomized error added. After a ...
7
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4answers
171 views

Seeking Literature on coordinate transformations?

I am looking to hone my skills in the theory and the mathematicas involving the projections systems, projection transformations ( from xy to uv, φλ and vice versa). Can you share the books/pdfs/...
6
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3answers
3k views

Convert UTM northing and longitude to latitude

I am doing some work with the Military Grid Reference System (MGRS), which is based on Universal Transverse Mercator (UTM). I find that I need to convert from UTM northing and longitude (actually, ...
2
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1answer
1k views

Calculate surface area from horizontal area and angle

I have a shapefile includes polygon features of tilted solar panels and I used "Calculate Geometry tool" in ArcGIS to find out the projected area of solar panels (horizontal area). I am looking ...
2
votes
2answers
855 views

Calling a QgsProcessingAlgorithm from a Processing python script in QGIS 3.0?

I am writing a Processing python script based on the template provided here. I am creating lines (destined to the 'OUTPUT') and I would like to clip them according to a polygon entered as the '...
0
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1answer
24 views

qgis:deletecolumn in QGIS 3 graphical modeler

I want to use the algorithm qgis:deletecolumn in a graphical modeler. How do I have to fill the case Fields to delete : ["field1","field2"] "field1","field2" field1,field2 [field1,field2] And is ...
2
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0answers
52 views

Getting minimum distance of points with scalable algorithm

I have a number of geographical coordinates with latitudes/longitudes: id | name | lat | lon 1 | New York | 40.730610 | 74.0060 2 | Philadelphia | 75.1652 | 39.9526 3 |...
1
vote
1answer
104 views

Performing isochrone in PostGIS by pgRouting?

In pgr_drivingDistance for isochrones the person who answered, missed to say the explanation of the answer about what function used by him to get the output for isochrone. I want to do the same but I ...
1
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0answers
46 views

Simplifying Multiple neighbouring Polygons, removing gaps and overlaps

My main goal is to simplify multiple polygons, avoiding overlaps and gaps between them. My initial approach was: Find intersections for each polygon so that I end up with an array of polygons, each ...
2
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0answers
29 views

Seeking method for determining survey points?

I'm trying to write software to create a topographic map, my goal is to select several points of interest and create a minimal mapping that is inclusive of the points and interpolates the topography. ...
3
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0answers
81 views

How to create equidistant points along lines (network)?

I am trying to create points at every X meters along a set of lines that represent a network. As suggested in QChainage doesn't place points evenly along dissolved lines I managed to this ...
41
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3answers
37k views

Why is law of cosines more preferable than haversine when calculating distance between two latitude-longitude points?

In fact, when Sinnott published the haversine formula, computational precision was limited. Nowadays, JavaScript (and most modern computers & languages) use IEEE 754 64-bit floating-...
2
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1answer
424 views

Client-Side Polygon split

I wanted to know if there is a way to split a polygon using JavaScript. So I have a web map which uses Leaflet API, and the user needs to cut polygons which are shown in the map using a straight line. ...
0
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0answers
62 views

Seeking Python implementation of contiguity constrained clustering?

I'm looking for an example of Python implementation of contiguity constrained clustering algorithm. The task I want to perform is to reduce the number of administrative zones by grouping them into as ...
1
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0answers
123 views

QGIS Python AttributeError object has no attribute 'pushVersionInfo'

I am unable to use almost all of the processing toolbox features in QGIS. I keep getting the following Python error across multiple algorithms: AlgorithmDialog.py", line 208, in runAlgorithm self....
0
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0answers
29 views

Algorithm(s) for Sensor Footprint at limbs

Is anyone aware of algorithm(s) that have been developed for computing remotely sensed image footprints that handle body limbs? The limb is the edge of the body / atmosphere where only the blackness ...
2
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0answers
32 views

Algorithm “qgis:difference” returns multiple heterogeneous outputs

I use the qgis:difference algorithm but it returns multi-type outputs. Sometimes it's a QgsVectorLayer but sometimes a str such as : output_.... My question is : when the algorithm returns an empty ...
4
votes
1answer
135 views

Match linestrings using Fréchet distance

I have two datasets of roads (both in WGS84). One has nicely digitized geometries, but lack some of the attributes and the other has heeded attributes, but digitized terribly. I want to transfer ...
6
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0answers
212 views

Packing squares polygons in a raster grid

In the green area of the raster I have to fit as many square polygons as possible, of three different sizes: 3x3 cell size 2x2 cell size 1x1 cell size With the fact that the approach should be ...
9
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4answers
4k views

Exploding overlapping to new non-overlapping polygons?

Given multiple polygons that overlap in multiple ways, I would like to export from these features all polygons that don't overlap with others, iteratively. The product would be a number of features ...