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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Algorithms for finding nearest road
Having two LineStrings I want to know if they actually are the same gps path or not. I guess something like if the distance between these are lower than x for a few points I would assume that they are ...
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ENDISI calculate
I'm new to ArcGIS. Can someone tell me why my ENDISI always equal to 1?
My algorithms:
("band02.tif" - 16170.19 * (("band06.tif" / "band07.tif") + "mndwi.tif" ^ ...
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Seeking algorithm for polygon straightening
I have a polygon that looks like this:
I want to get a result that ideally looks like this:
The best that I can come up with is a polygon simplification using shapely in Python:
Which algorithm ...
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Clustering Algorithms for Geospatial Data
I am new to the world of Geospatial Analysis!
I am interested in learning about Clustering Algorithms that can be used for Geospatial Data.
For instance, suppose I have:
A shapefile for all ZIP Codes ...
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How to use v.net.path algorithm on QGIS?
I want to use the v.net.path (see grass documentation) from the QGIS processing toolbox. However, I do not know what the format of the input parameters is. The required parameters are:
Input vector ...
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Find areas distant from any points
I want to draw all areas that are far enough away from any single point of a layer, in this case they are Openstreetmap building=yes tags and I want to calculate the areas that are completely clear of ...
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Algorithm for breaking polygon into squares [duplicate]
We've got some code in our Java application that breaks up polygons into grids for a bunch of reasons. One is to more efficiently spatially index coastal regions (the bounding box tends to cover the ...
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How Neighbor Contiguity Algorithm actually works
I want to identify neighbors based on queen or rook contiguities in a programming language that does not have the feature yet. I know that tools like spdep, pysal, geoda, and ArcGIS all implement this,...
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Seeking algorithm for finding shortest path around obstacles
I am seeking an algorithm, not GIS software.
To find the shortest path between two points at sea with land between them, you can consider land as a polygon shaped obstacle between these. The concept ...
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Are there any registration algorithms for registering a LiDAR frame to a larger point cloud?
I need to georeference a set of LiDAR frames using a larger (already geoereferenced) point cloud. The LiDAR frames are always a subset of the point cloud, usually a lot smaller. A typical frame has a ...
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How to check if there is an arc within a polygon (algorithm in geometry) [closed]
Now I have a polygon with arc like this:
I need to check if this polygon contains arc or not. How can I do that using geometry?
Clarification about the reason why:
I need to know how to detect in &...
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Calculating total ascents greater than 50m
Calculating total ascent is a relatively common GIS problem.
Given a set of height data (eg from GPS, or from draping a track over a DEM), I am interested in calculating total ascents where each ...
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Crash when running algorithm via PyQGIS plugin
I use a Python plugin which is working great on my computer. But on another one, I get an error at the execution of an algorithm from processing package in PyQGIS:
## Report Details
**Python Stack ...
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QGIS - Graphical modeler - output shapefile is not altered
Graphical Modeller
I started using Graphical Modeler in QGIS (learned about it few weeks back and I was really excited about this). Unfortunately (probably due to lack of skill) I cannot seem to make ...
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Convert radar parameters to polygon
I have the following list of parameters for a given radar:
Latitude
Longitude
Coverage lateral
Coverage horizontal
Max Range
Power Emitted
I would like to convert these parameters to some type of ...
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Identify the algorithm (not code) for QGIS native tools
The question
For someone with no knowledge in C++ (programming language used to write QGIS code), is there a way to identify based on which algorithms the different QGIS native tools are written?
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Merge vectorlayers and attributes in QGIS
I am writing a script to run in QGIS and one thing I am trying to do is to merge a row of layers and their attributes. So if one layer is overlapping with another there should be created a new object ...
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Creating custom processing tool (sibling of Batch Nominatim geocoder) in QGIS
I want to create a custom processing tool for geocoding in QGIS.
It will reproduce the "Batch Nominatim geocoder" geoalgorithm, besides several things:
another URL of a geocoder will be ...
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Distance between a point and a geodesic line?
On the earth surface (a spheroid, not a sphere), point A and B defines a geodesic line L, and point C is not on L. Solve the distance between C and L (i.e. let P be a point on L, find the minimum ...
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Use polygon lines to create masks
Given a tile (the cropped base map in the left) and polylines (red lines), is there any tool/workflow in QGIS to convert them into masks in the right?
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Generating rectangles that fit within a country polygon, to use for roughly finding the country with minLat/maxLat,minLon/maxLon
I want to figure out how to automatically create/generate rectangles within all countries, similar as I have done, manually in QGIS, with Norway as shown in the image below.
I know there is no perfect/...
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How to colorize hierarchically-ordered polygons?
I have to implement a solution for coloring a lot of polygons that are derived from a hierarchically-ordered dataset. The dataset can be compared to a family tree in terms of hierarchy. Most of the ...
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Detecting and making all connected lines in the same direction in QGIS
I have a list of straight roads segmented which has a unique "ID". I would like to detect connected lines in the road network and make them in the same direction instead of reversing them ...
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Zip output of QGIS Processing Algorithm
I want to make a script which
processes some algorithms with multiple layers as inputs
outputs some results in QGIS project
then save the layers as zip files in a specified folder
I have not been ...
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Output singlepart features by default for tools and algorithms in QGIS
In QGIS, many algorithms and tools return multipart geometries. For further processing, a conversion Multipart to singleparts is necessary. This is a bit cumbersome.
To make just one example: when ...
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Passing selected layer-feature inside QgisAlgorithm (in code)
In our algorithm, we do three steps:
call Algorithm A AlgoA,
takeResultLayer into lyr from AlgoA output,
for each feature of lyr we want to run Algorithm B AlgoB .
Code of my processAlgorithm looks ...
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Processing algorithm as expression in QGIS
I would like to be able to set an expression as the default value of an attribute (in layer properties-->attributes form) which uses an algorithm from the QGIS toolbox.
In this case, the algorithm ...
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PyQGIS 3: Cannot Pass Memory OUTPUT To Next Processing Algorithm As INPUT
I am attempting to convert some ArcGIS arcpy command-line scripts to PyQGIS and am running into a problem working with memory layers. The script takes several vector files as input and progresses ...
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Finding largest circle which entirely included in multipolygon and not containing any point of points layer
I have two layers*:
1 MultiPolygon (the complex green features)
1 MultiPoint (many thousands of yellow dots)
How can I efficiently find the largest circle (center coordinates + radius) which is both
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Seeking algorithm other than Convex-Hull to avoid overlapping polygons
I want to draw polygons with no overlap, based on sets of points. If I use Convex Hull algorithm to deduce the boundary polygon, it's pretty obvious that the resulting polygons WILL overlap. Is there ...
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Least cost path algorithm in SAGA?
I'm very new to this topic.
I have to calculate the least cost path between two points for a school project and found this tutorial: https://dges.carleton.ca/CUOSGwiki/index.php/...
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Connecting points with Z values to lines where the Z values are retained in the nodes of the resulting line
I have interpreted seismic data as xyz-points (about 23 cm lateral resolution). They are not really ordered but rather a simple list of coordinates. One file contains multiple seismic "lines"...
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How can I cover an AOI with a subset of image extents?
I’ve been experimenting with a problem that I have not found a friendly and simple solution for yet. Curious to know if any of you have already solved this problem.
Given a AOI and a set of image ...
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What is algorithm name for "Count Points in Polygon" using PyQGIS?
I want to count points in polygon, using PyQGIS. When I check the documentation, I find the description of the {parameter_dictionary}, but not the algorithm name which must also be provided.
What is ...
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Simplify a branching line string
I have been working on developing a GeoTools function to create a central label line for polygons.
The idea was to grab the skeleton of the polygon and use that to place my label, however it turns out ...
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"Rounding" GPS coordinates based on uncertainty range
A stationary GPS receiver will produce a random cluster of coordinate points around its actual location. I can look at previous coordinate readings and apply various algorithms to find the "...
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Shortest-path algorithms used in Networkx: what about points not near nodes?
I am new to Networkx, but am I right that Dijkstra's is the algorithm Networkx uses by default? From what I understand, Dijkstra's algorithm traces a shortest path between two nodes on a graph. What, ...
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Automatically create points based on algorithm
I have a shapefile with points representing the sightings of different bird species on different dates (in ArcMap 10.4.1). I now have to create a new shapefile with points for bird territories. A ...
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Are there any mass-preserving raster projection algorithms?
Raster maps (e.g. as a GeoTIFF) can be reprojected using tools like gdalwarp. While these tools do a decent job to project images, they are not truly mass-preserving, i.e. the total sum of the values (...
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Determine how regular a set of points is?
I'm trying to cluster some gps data to accurately determine stop points for vehicle movements on a testing grid. I know the points they stop at are regular/closely match points on some defined grid of ...
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Genetic algorithm based microphone array placement for optimum acoustic coverage [closed]
I am trying to find the optimal location for the placement of the microphones. I want to reduce the no of microphones place on the given area of interest. I want to use minimum no of microphones to ...
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QGIS: No values in field after creating spatial index
I want to join a vectorlayer with a grid using the algorithm "join attributes by location (summary)". It took hours to execute, but it worked. Then I found This thread which told me I have ...
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Problem when running the Clip Raster by Mask Layer - Layers were not correctly generated
I need help, this is for my Final Year Project.
Yesterday before I did something on my QGIS, I can run the mask layer but suddenly after I followed a tutorial on youtube on how to do 3D Map, I cannot ...
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Algorithm to find low/high atmospheric pressure systems in gridded raster data
What's the commonly used algorithm for finding center positions and values of low/high atmospheric pressure systems in gridded raster data (GRIB/NetCDF/GeoTIFF)?
First I tried a naive approach to ...
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Creating a loop itinerary
I am trying to find a way to create a loop itinerary. For example, I know my starting position, and I want to walk some distance and come back to my starting point.
It's quite easy to find itinerary ...
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Doing TIN Interpolation in QGIS
I want to do TIN Interpolation on a layer but when I fill all the fields with the right data (vector layer, interpolation attribute, extent etc) the algorithm does not run and shows me this message:
...
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What algorithms can be used to create a DTM from a DSM TIFF file i.e that will reduce or exclude features such as trees and buildings [closed]
I am using Python and QGIS. I have obtained - purchased - a 1m DSM photogrammetry data file - a TIFF. I could purchase a DTM from the same company, but they are 5m grid, and so they lose some data I ...
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Landsat footprint artifacts in statewide CCDC map
I have produced a map for New York State using CCDC as implemented in google earth engine. The map counts the number of disturbances for each pixel occurring between 1990 and 2019 (black = 0 ...
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How to define the spatial distance ε for EDR and LCSS similarity algorithms?
Let's assume a dataset with human trajectories like Geolife. I want to measure the similarity of two random trajectories from this dataset using the EDR or/and LCSS algorithm(s).
I wonder, which ...
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What is the algorithm that Shapely used to check if two polygons intersect?
What is the algorithm that Shapely used to check if two polygons intersect?
from shapely.geometry import Polygon
p1 = Polygon([(0,0), (3,0), (3,1), (1,1), (1,2), (3,2), (3,3), (0,3)])
p2 = Polygon([(4,...
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