Questions tagged [nearest-neighbor]
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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27 views
PostGIS DISTINCT ON clause
I have two tables
essa -- thousands of polygons
narrowed -- few hundred parcels
My goal is to find the closest parcels to each essa polygon. it happens to be many of the parcels are the closest ...
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1answer
17 views
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 ...
2
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0answers
65 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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1answer
48 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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23 views
Correcting boundary effect on GIS spatial analysis?
I have 250 zones in ArcMap, and I calculated RNN for points of each zone with nearest neighbor analysis tools.
How can I correct edge effects in GIS?
2
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1answer
27 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 ...
3
votes
1answer
46 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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1answer
35 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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1answer
54 views
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 ...
1
vote
1answer
62 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 ...
2
votes
1answer
72 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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2answers
62 views
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 ...
4
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2answers
87 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 ...
3
votes
1answer
85 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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votes
1answer
25 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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0answers
60 views
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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0answers
43 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 (...
1
vote
1answer
46 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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vote
1answer
85 views
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 ...
2
votes
0answers
73 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 ...
0
votes
1answer
48 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!
...
2
votes
2answers
152 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 ...
2
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0answers
95 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 ...
1
vote
1answer
68 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 ...
1
vote
1answer
168 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 ...
1
vote
1answer
42 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)....
2
votes
1answer
84 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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0answers
65 views
Nearest neighbour raster values only in specific zone
This is a follow up question to my previous post and someone else's post:
I would like to replace NA values in raster with average nearest neighbour values, but ONLY in specific zone of the raster:
...
3
votes
2answers
96 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(...
3
votes
1answer
197 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:
...
3
votes
1answer
237 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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vote
2answers
101 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:
"...
2
votes
3answers
372 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 ...
1
vote
1answer
80 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....
1
vote
2answers
34 views
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 ...
4
votes
1answer
299 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 ...
2
votes
0answers
116 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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0answers
114 views
Neighborhood operation within raster using python
I want to perform a neighborhood operation on a raster which will take pixel values in 8*8 window and run through entire raster image (in .tif format). Can anyone suggest any useful python documents ...
5
votes
1answer
95 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():
...
1
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0answers
68 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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0answers
52 views
When does nearest neighbor PostGIS query need to be measured in meters?
When you use geography type in postGIS, the default measurements are in degrees. There are numerous approaches and I cannot decide which one is the best.
In "PostGIS in Action" book (ISBN: ...
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1answer
84 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 ...
1
vote
1answer
234 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 ...
2
votes
1answer
391 views
What function can I use in R to classify 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 ...
4
votes
1answer
99 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,...
3
votes
1answer
276 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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0answers
490 views
NNJoin distance output in metres instead of decimal degrees
I'm a beginner using QGIS 2.18.
I have two vector layers, one consisting of multiple points identified by lat&lon (these are points marked at sea) and another consisting of a line feature (...
5
votes
3answers
339 views
Clustering neighboring points inside ArcGIS Desktop?
I am using ArcGIS Desktop 10x.
I have a shapefile of 300 points which I need to make groups, each of which will contain exactly 9 points which are closest neighbors.
I tried the 'near' tool, ...
0
votes
2answers
69 views
Loop to caculate NNI with spatialEco
In R, I need to calculate the nearest neighbour index between the relocations of a single animal, for several different individuals. I want to determine whether the relocations of certain individuals ...
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0answers
218 views
QGIS Nearest Neighbor Analysis on Layer Subsets with User Defined Area
I have a data set of developments of various types in a single US City. My aim is to run a nearest neighbor analysis for each of the various development types to explore how clustered, random or ...
