Geographic Information Systems

Questions tagged [nearest-neighbor]

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A technique for resampling raster data in which the value of each cell in an output raster is calculated using the value of the nearest cell in an input raster.

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NearestNeighbor producing bad quality tiles

I have been using Bicubic interpolation to render some basemaps because this produced good results. This is what I get when using Bicubic: However, when using Nearest Neighbor interpolation, a white ...
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Finding nearest 10 observations that occurred 2 years before original observation using ArcGIS Pro ModelBuilder?

I have a point sample of house sales (~42k points over 9 year period) with a date field(integer), and for each point I want to find the 10 nearest houses within a year of sale and also which were sold ...
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How to get Memory layer dispalyed in Vector Panel List using Pyqgis?

I have two point layer in my Project Centroid.shp and Nodes.shp.I have used Distance Matrix to find nearest Nodes point from Centroid Point. I have saved the output in FinalDistance.csv. The ...
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45 views

Error creating DEM with Nearest Neighbour tool in QGIS?

I have an issue when I am creating a DEM with the tool natural neighbour on QGIS. When I extract my data directly on Qgis I have no issue creating a DEM. My points are coming from different sources ...
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Neighborhood Analysis with ArcGIS Spatial Analyst to Calculate Percentage

I have a raster file where the cells (1 meter) are classified as 1 (forest) and 0 (non-forest). I would like to create another raster (1 meter) where each cell is given the percentage of cells within ...
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Combining st_join with st_nn to include all points within, as well as within a given distance of a polygon

This is a follow up to my earlier question (Spatial join in R - Adding points to polygons with multiple corresponding points). I have successfully joined a spatial points file to a polygon file in R ...
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Nearest Neighbor - return object ID in R

I have a csv file that contains the GPS coordinates of about 100 villages and their unique ID. I have an other csv file with the GPS coordinates of some potential destinations and their unique ID. I ...
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PostGIS - Nearest Neighbour Join to sum values

I have a table of polygons T1 and a second table of points P1 Each point has a value I want to sum the values of P1 for each T1, with P1 being the closest set of points to T1 At the moment the only ...
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95 views

Find the closest Point from a Point which contains the same attribute

I am trying to create python code to iterate through points on 1 layer and find the closest point on another layer (Road Chainages) based on attribute values. I need to limit the search to < 20m ...
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Seeking package/function in R that can help tag GPS coordinates of fauna sightings to nearest sampling point?

I have 1 dataset of animals sighted walking a survey, and I would like to tag them to the respective sampling points along a transect. Any idea what function/package in R can do that? Maybe ...
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367 views

Nearest Neighbor Analysis Results

I'm fairly new and entirely self-taught in using QGIS 3.4. I'm looking at turtle nest sites and trying to run a nearest neighbor analysis to analyze their distribution and establish whether or not ...
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257 views

Spatial join attributes based on closest point in PostGIS

I have two point tables from which I want to extract a value from one table to the other, based on the nearest distance of those two points. t1 t2 id | value id 1 | 100 1 ...
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42 views

How to find the closest stop point PostGIS

I have Point geometries created from lat,lon I loaded all the 10,000 stops in a certain city using gtfs i would like to query my db to find the closest stop reference to my point. the staypoint ...
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67 views

Getting the distance traveled across road segments

so I have a query that takes an encoded polyline, segmentizes that polyline into smaller pieces, and matches each point on that segmentized line to a "road segment" from a separate table in my ...
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169 views

PostGIS -> LineString + PointZ = LineStringZ

DATA I have 2 tables in PostGIS: linestable with MultiLineString geom surveypointtable with Point + elevation attribute GOAL The goal is to rebuild the lines as 3D replacing line's vertices with ...
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SRTM/DEM 1m resolution (batymetri) to point [closed]

I have bathymetry data (1 huge data) = SRTM/DEM/FGDBRaster (0,9818m resolution pixel, floating, 32 bit, 45 GB size) and an alternative data (split into small pieces data) = same data but with 1m ...
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215 views

A line between point to nearest neighbour point using QGIS

I have a layer of points in QGIS which represent electric poles How do I create a polyline layer that would have lines running between the poles so it can represent the the electric cables that ...
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247 views

Efficient way to find nearest feature between huge postgres tables

I have two tables (g1 and g2), both with around two million features. I need to know for each feature in g1, which is the closest feature from g2, with a condition. Since they are both so huge, I also ...
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Excluding point from Nearest neighbor search once it's been matched using R?

I have two lists of addresses, List 1 and List 2. I want to find the nearest neighbors of the list--but without assigning more than one point to any point. So say point 1A is the nearest neighbor of ...
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135 views

Query takes very long time

I'm a newbie to POSTGIS and I wonder if someone could help me out. I have loaded all postal codes with their geographical coordinates (geography) and created an index on this coordinate. When I run ...
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119 views

Get closest road-segment to segmentized LineString points

So I have a table that stores a bunch of traffic counts for various road segments across the country. I'm regularly getting real-time location data from vehicles that are moving around a given region ...
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64 views

Query to return closest LineString given a Point [duplicate]

I have a road lines data in a table with field roads(id SERIAL ,the_line geometry(LineString,4326)) suppose an accident occurs in a middle or at any location in that waterline i want to stop the ...
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Interpolation in QGIS shows wrong output result [closed]

I have done interpolation (IDW and Nearest Neighbour) in QGIS. But interestingly the output shows the wrong result. The area where I have a huge number of points results in a lower Z value (it is ...
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101 views

Nearest Neighbour Analysis Or NN join

I have two Layer in my Project 1) Voronoi Layer which is constructed on point Layer 2) Building Layers which is represented as Polygon. The goal is to find the nearest node for every polygon (...
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56 views

No module named 'mmqgis'

I have two layers in my Project 1)Points Layers 2) Polygon Layer I need to apply nearest neighbour Analysis between point and Polygon, but i am unable to get . I tried the below code.I am using ...
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Constructing Voronoi Polgon and Applying Nearest neigbour in it

I am learning QGIS 3.XX and currently working on Voronoi Polygons. I have three layers Point layer Building Layer Population CSV file. These points layer are basically water tanks and building ...
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178 views

Geo-hash finding nearest neighbour with massively variable distance to actual nearest neighbour

I have a series of points in lat-long space, ranging from having their nearest neighbour very close to 1000s of km away. Say I do a geo-hash of these to a high precision, my search of nearest ...
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139 views

Optimizing a nearest neighbor search in PostGIS for a large dataset

The below code is working well for smaller datasets, however I want to use this with a 30 GB table. Every time I run it using the larger table I run out of SSD space, the table gets to 127 GB in size! ...
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434 views

Nearest Neighbor

We've got a table of approximately 300,000 points and would like to find the nearest neighbor (within 10km) to each point in the same table. The most efficient query we've found so far is below, but ...
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157 views

Find the nearest neighbour for points in one layer to points in another, then measure the distance

USING QGIS 2.18.19 with python console (planning to upgrade to the newest QGIS after this piece of programming) I am struggling with finding the correct pyQGIS coding for this. I have a shapefile ...
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117 views

For each row of GPS coordinates, get value from nearest road to coordinates and copy to said row using PostGIS? [closed]

I have two tables in my database; one contains a set of GPS coordinates of a car which have been converted to geom, and another containing Open Street Map road data, including the speed limit for most ...
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1answer
229 views

Nearest point on line from a point in PostGIS and its attribute value

Consider the following image; I have points (shown in blue circles) stored in my database with their geometry and an attribute value. Additionally, I have another table with User Points (yellow ...
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52 views

Get barrier edge id

I have a table of POINTs that represent barriers. I would like to be able to find the closest edge id on the edge graph so that I can have the routing algorithm ignore that edge (thus route around it)....
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1answer
127 views

QGIS 3.0.2 NNJoin doesn't complete. Crashes when close status bar

I have run a large spatial point to polygon join of 2 million points to 657 polygons. I used NNJoin so that the closest polygon will be assigned to a point if the point does not lie within one. The ...
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135 views

Nearest Neighbor search in PostGIS using cases

I am using the following PostGIS nearest neighbor query to determine how close a point is to an area (polygon) that has been flooded and it's working well: SELECT ST_AsText(ST_SetSRID(...
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1answer
571 views

How to UPDATE with LATERAL Nearest-Neighbour query?

Say I have table gps like: CREATE TABLE gps( gps_id serial primary key, measured_timestamp timestamp, geom Geometry(Point,4326), stop_id int --Null ); And I have a table of stops like: ...
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1answer
369 views

Merging overlapping polygons with original polygons in QGIS

I have a large vector shapefile dataset containing polygons, many of which overlap. I want to assign each overlapping section to one of the original overlapping polygons. E.g. if polygon A overlaps ...
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140 views

ST_ClosestPoint usage in QGIS 3.0

I try to use ST_ClosestPoint function to find the closest point to find the MultiLineString layer. My line layer (Reach) has 42 attributes and point layer (Stations) has 7 attributes. My code is: "...
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3answers
525 views

Projecting GPS point to point in closest pgrouting road (map matching)?

I'm quite new to PostGIS and pgRouting. I'm interested in doing a simple map matching. Precisely, finding the closest point in a given OSM road network. I’ve successfully imported the OSM network ...
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102 views

Intersection with closest point using PostGIS?

I'm trying to update the field of a point table with a value from a linestring one : update object_elevation set contour_elevation = c.contour from contours c where st_intersects(st_ClosestPoint(c....
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elevation difference along the border of two categories GRASS

Consider the following raster with two categories and a DEM (numeric raster), I'd like to compute the elevation difference along the border (closest pixel) of those two categories, it doesn't matter ...
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1answer
448 views

Returning Multiple Nearest Neighbors

I'm trying to replicate a nearest-neighbor analysis that returns X (one OR more than one) neighbors in either QGIS or PyQGIS. For example: In this output, I have a set of locations (Red Stars) that ...
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145 views

How to solve Python error for raster analysis interpolation nearest neighbor in QGIS [closed]

I am trying to interpolate temperature values into a raster using QGIS 2.18.15 in Windows. I need the output file as a GeoTIFF (.tif) file. I have my input for temperature already in a shapefile, but ...
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1answer
147 views

QgsSpatialIndex.nearestNeigbor() unexpected result

I have a Linestring layer for which I have build a QgsSpatialIndex with the following code: my_linestrings_lyr_idx = QgsSpatialindex() for f in my_linetraings_lyr.getFeatures(): ...
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90 views

create neighborhood list in R with large dataset

I want to create a weight matrix based on distance. My code for the moment looks as follows and functions for a smaller sample of the data. However, with the large dataset (569424 individuals in 24077 ...
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1answer
129 views

Nearest Neighbor Analysis returning 0 for Observed Mean Distance

I am working in QGIS 2.18.14 to which i am fairly new. I am trying to perform a nearest neighbor analysis, however it returns 0 for the observed mean distance. the expected distance is also an ...
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1answer
305 views

Nearest Neighbour Pixel Value Google Earth Engine

I want to attach the values from one raster to another raster. Using simple band math I can multiply the value of the base raster which is the presence of mangroves and therefore 1 or masked by the ...
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1answer
513 views

Classifying raster that takes neighbours into account?

I am working on classifying forest types using Sentinel-2 satellite imagery (10-m resolution; band-2, band-3, band-4 & band-8). I have ground-truthed field data as a training set. I want to set a ...
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1answer
133 views

Faster way to find nearest neighbors with LASlib?

I'm using LASlib to find the nearest neighbors of a subset of points in a point cloud. I'm using brute force to find nearest neighbors, which is extremely slow (my code below). Is there a better way,...
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1answer
406 views

Finding the nearest line to a point in QGIS,but Not Work

I saw Finding the nearest line to a point in QGIS? I wanted to create a program to get the line closest to the selected point. Here is the code. dPos = mouseEvent.pos() qpoint = ...

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