Questions tagged [centroids]

In geometry, the centroid, geometric center, or barycenter of a plane figure or two-dimensional shape X is the intersection of all straight lines that divide X into two parts of equal moment about the line. Informally, it is the "average" (arithmetic mean) of all points of X. The definition extends to any object X in n-dimensional space: its centroid is the intersection of all hyperplanes that divide X into two parts of equal moment.

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44
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11answers
95k views

Obtaining up-to-date list of US ZIP Codes with Latitude and Longitude Geocodes? [closed]

NOTE: This began as a question on Stack Overflow, which has subsequently been closed. I also noticed a similar question about Most Up-To-Date Source for US Zip Code Boundaries, but I believe this ...
41
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3answers
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How to calculate polygon centroids in R (for non-contiguous shapes)

I've spent a little while figuring out the answer to this question. It's not immediately obvious from a Google search, so thought it may useful to post the answer on here. There is also an additional ...
37
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1answer
34k views

Finding center of geometry of object?

Given a set of 2D or 3D points: How to find the center of geometry of an object? According to the following figure, the center of geometry differs from the center of mass if it is calculated in the ...
33
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8answers
57k views

How to determine the centroid of polygons?

I have a polygon vector and I want to quickly attain the centroid of this polygon for insertion in a text document. I am working with QGIS. I searched through other questions and although some are ...
27
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2answers
71k views

find the centroid of a cluster of points

While searching the web, solutions for finding centroids of polygons come up rather often. What I'm interested in is finding a centroid of a cluster of points. A weighted mean of sorts. I would ...
16
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3answers
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List of central coordinates (centroid) for all countries?

I need a list of the central points (centroid) for all countries: China: lat/long (coordinates of the most central point in China) France: lat/long (coordinates of the most central point in France) ...
15
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3answers
8k views

How to get the centroid of a set of points in PostGIS?

I use PostgreSQL with the PostGIS extension. I have a set of points in the_geom column from a table myschema.myobjects. I want to create a select statement to get the centroid of this cluster, so ...
13
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2answers
2k views

Centroid coordinates for odd-shaped polygons

I have a problem in computing the centroids of certain polygons in QGIS (via the geometry tools): for certain polygons - with a strange and rather long shape - the centroids computed are off the ...
12
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1answer
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How to take polygon centroid in Postgis

I have table with column name,Latitude and Longitude.I want to update this with polygon name and its centroid latitude longitude.I know there is a function in postgis st_centroid(geometry). But I want ...
11
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2answers
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Calculating a spherical polygon centroid

I'd like a general way to calculate centroids for polygons on a sphere. So far, the best online reference appears to be: Tools for Graphics and Shapes by Jeff Jenness. The method described there ...
11
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2answers
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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 of ...
10
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2answers
3k views

PostGIS - Get a point inside a line or polygon

I need to get the center point of a line or polygon to make marker for my app. So that when you click a marker the geometry appears (line or polygon). I used ST_Centroid to make it work. The result ...
10
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1answer
2k views

How exactly is the centroid of polygons calculated?

I would like to know how exactly QGIS Geometry tools -> polygon centroid is calculating the point coordinates. For example does it divide the boarder of the polygon into small points, take two pairs ...
10
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0answers
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How to add Lat/long columns to a point layer which is not in WGS84? [duplicate]

I need to extract the Lat/long coordinates of the centroids of districts. My QGIS project SCR and the different layers have all been set on "WGS 84 / UTM zone 18N". I've created the centroids using ...
9
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3answers
8k views

Using Field Calculator in QGIS to update columns with centroid coordinates

In QGIS I would like to update two columns with the centroid easting and northing of my polygons. I am using the field calculator. I have tried using $x and $y but this only seems to work for points. ...
9
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4answers
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assign and move centroids to their polygons

I m using QGIS 1.8 Lisboa. After calculating the centroids from a polygon shapefile, if some of them lie outside the polygon outlines, I'd like to move them on the polygon they came from. The ...
9
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1answer
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calculate {minimal} distance between polygons in R

I have calculated the surface area of species distributions (merging polygons from shapefiles), but since this area can be comprised of quite distanced polygons, I would like to calculate some measure ...
9
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1answer
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What is the difference between data access's “SHAPE@XY” and “SHAPE@TRUECENTROID” tokens?

Data Access Search Cursor. What, if anything, is the difference between the tokens "SHAPE@XY" and "SHAPE@TRUECENTROID"? They returned the same coordnates on a test polygon: >>> cursor = ...
8
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1answer
10k views

Calculating Centroid of all lands of Earth using SQL Server Spatial?

I want to find the center point of all lands of the earth. What I have tried up to now is downloading shapefile of all countries and polar parts of the earth. Then I imported that shapefile into a ...
8
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1answer
155 views

Getting dual graph from QGIS?

I have a .shp file, and I need to get the dual graph from this file (that is to say, each polygon centroid should become a vertex, and two vertices are linked if their associated polygons are adjacent)...
8
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1answer
2k views

How to create point labels from midpoints of road polylines in QGIS?

I have a road polyline layer (singlepart ie has several features per road, grouped by an id field), and i want to (after merging the parts) find the mid point of the resulting lines. This is for roads ...
7
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3answers
527 views

Creating centerline of river in QGIS? [duplicate]

I made two river bank lines and I want to associate them. I want to make a centerline using two rows as a base. I managed to make the centre line with a lot of work creating several lines from one ...
7
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2answers
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How do I calculate a weighted centroid with respect to a raster, e.g. population weighted centroid

In ArcGIS 10.0, how do I calculate the weighted centroid of a collection of polygons, where I want the weight to be a raster layer. In particular I am using a raster of population counts and would ...
7
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3answers
2k views

How to place multiple symbols on one polygon centroid?

I am using QGIS for visualizing the health conditions of elderly living in an old age home, some of the elderly have multiple medical device with them and I want to show them on the map. Suppose I ...
7
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1answer
667 views

Zip + 4 Centroids

I have a data set with ZIP +4 codes, and ideally, I'd like to map them (their centroids) as points. I'm not interested in their boundaries (since they're not really geographies anyway). Does anyone ...
7
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1answer
4k views

Polygon Centroid Options and Appropriateness (FeatureToPoint, Labels, etc)?

I've found a couple of other Stack Exchange questions related to this, but they were not satisfying. For example: How does ArcGIS Desktop calculate INSIDE point for Feature to Point? does not tell ...
7
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1answer
381 views

Connecting centroids of lines sharing same intersection in QGIS?

I have this street network of the center of Turin (IT), composed by lines representing streets, and black points representing intersections. I have computed the centroids of each line and displayed ...
6
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2answers
1k views

Identifying cluster centroids using ArcGIS Desktop?

I have a data set of points which are grouped into clusters like so: I'd like to use ArcGIS or Python to create a point layer of the centroids of each cluster but I can't seem to find the right tools....
6
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3answers
12k views

How can I calculate the center point inside a polygon in ArcGIS 9.3?

I'm using the JavaScript API 1.6 on ArcGIS 9.3. I have a polygon geometry in an ArcGIS map, and I'm trying to find a way to get the point that lies in the exact center of the geometry. What is the ...
6
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2answers
1k views

Сalculate polygon centroids with 'point on surface' function

I want to calculate centroid coordinates X_center and Y_center for every polygon in layer so that in case polygon has not simple shape (e.g. with holes or like in the picture below) centroid will be ...
6
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1answer
1k views

How to force QGIS Centroid Fill inside the Polygon?

I would like to use a centroid fill to enable me to place a letter inside a polygon. The advantage of using a centroid fill is that it also shows up in a legend, whereas labelling the layer would mean ...
6
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1answer
317 views

How to assign polygon attributes to grid cells using centroids in QGIS?

I am relatively new using QGIS. Unfortunately I can´t figure out the following yet. I have two polygon shapefiles, one is a grid I have created using QGIS 2.12.3-Lyon (Creat graticule) and the ...
5
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2answers
897 views

Computing radius of gyration in PostGIS

The radius of gyration is a measure of the standard deviation of distances between points (and their center of mass), i.e., how frequently and how far points are moving. A formal definition is: I ...
5
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1answer
109 views

Distance to Multiple Neighboring Sectors

I have two shapefiles - one of neighborhood polygons and another of centroids within those neighborhoods: For each centroid I would like to calculate: Distance to the next closest neighborhood (and ...
5
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2answers
585 views

QGIS giving multiple centroids per polygon?

I have a shapefile for the boundaries of European NUTS regions, and I would like to compute the centroid for each of those regions. When I do this in QGIS (2.6.1 on OSX, using polygon centroids from ...
5
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1answer
517 views

Rasterize in QGIS using point as centroid (not vertex)

I'm attempting to make the full switch from ArcGIS to QGIS, but there are a few snags I'm hitting along the way, one of which is in the GDAL "Rasterize" function. My process goes like this: I have a ...
4
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2answers
1k views

Getting centroids for multiple lines?

Is there a possibility to get the centroid of each line? When using VECTOR ==> ANALYSIS TOOLS ==> MEAN COORDINATS I always get a centroid of the whole lines. What I need is the centroid of each line ...
4
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1answer
2k views

How to use the field calculator's centroid() Geometry function in qgis 2.0?

There is an option in the field calculator for centroids under geometry which when you double click gives you "centroid( ". What information is required here in order to use this function?
4
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1answer
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How do I get the centroid of line with OGR

Can somebody explain how to get the centroid of a feature with ogr? I have no idea what the centroid() function itself does. >>> linelyr = lineshp.GetLayer() >>> f = linelyr....
4
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2answers
506 views

Misalignment when generating centroids with Qgis

I was wondering if anyone could shed a light on why this behavior is happening in QGIS ? I'm pretty confident that the issue here is not due to "centroids within polygon" Edit Added a detailed ...
4
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2answers
2k views

How to get mean coordinates of features from a point layer?

I have a vector layer containing several points and I would like to generate the mean coordinates of these points, using QGIS only if possible. I'm looking for something similar to centroids, but for ...
4
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0answers
888 views

Shapely polygons crossing the antimeridian

Sample data Consider the following WKT Polygon, crossing the international dateline (antimeridian): POLYGON((176 49,-65 49,-65 11,176 11,176 49)) And the following points: POINT(-140 32) # ...
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0answers
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Finding the “center of gravity” of multiple points where points have unequal weights [closed]

I'm trying to reduce a set of lat/lons (each with it's own weight) into one lat/lon that is the center of mass of all of the points. however when I map the results the average point falls no where ...
3
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1answer
490 views

Real centroid plugin QGIS3

I am looking to use realcentroid where I'm assuming it puts all points within the polygons rather than the tool in QGIS Vector -> geom -> centroid tool, which in my result some bendier polygons have ...
3
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1answer
2k views

Bind polygon centroid to polygon attribute data

I am trying to bind a dataframe containing polygon centroids to the polygon attributes. Here's what I've done so far to create the centroids: library(rgdal) library(PBSmapping) library(maptools) ...
3
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2answers
3k views

Finding coordinates of raster centroid? [duplicate]

How do I find the coordinates of the centre / centroid of a raster? I have tried Zonal Geometry but this does not give me the coordinates. I need to find the centroids of two rasters and create ...
3
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2answers
886 views

How to compute weighted centroids in PostGIS?

I have a group of points and each point has an associated count value. How can I calculate the centroid of the group weighted by the values associated to each point?
3
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1answer
61 views

Making path between polygon using QGIS?

I am trying to draw a line (vector layer) of a certain length that that tries as much as possible to dodge the green polygons. Assuming a starting point, is there some sort of line centroid ...
3
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1answer
590 views

Is there a method in SQL Server (2008 or 2012) that will return the equivalent of the Esri LabelPoint for geometry?

I'm looking for a method that is equivalent to the Esri LabelPoint for SQL Server Geometry (or fairly close). Does it exist by a different name? Or is there an after-market implementation? I found ...
3
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1answer
4k views

How do I convert longitude & latitude to a 3d (geocentric x,y,z) coordinate?

I'm interested in finding the centroid of a point cloud. I understand that to do this I need to convert latitude and longitude values to 3d coordinates, average them and then convert the resulting ...