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 ...

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How can I find the center of the circle or ellipse I just created

I need to draw circles and ellipses with a certain length/width/ radius. I used the rectangles ovals digitizing plugin to create them, but only measured roughly the circles' radiuses. It would be ...
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2answers
42 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?
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1answer
47 views

Looking for information on methods or algorithms used to calculate centroid from polygons across software

Looking for information on methods or algorithms used to calculate point centroids from polygons across software. ArcGIS uses a "gravity model" but can someone point me to the math or a paper on the ...
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2answers
50 views

Buffering points bounded within polygons

I've checked around and didn't see this one yet, hoping somebody can help me out (preferably without code, but I'm all ears). I'm using arcGIS 10.1 on an i5 win7 machine with 16g RAM. Not a xeon but ...
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78 views

OpenLayers: How to get *real* centroid of a Line Geometry/Feature?

I have declared a line geometry as: var lineString = new OpenLayers.Geometry.LineString([source,target]); then I am trying to get the centroid of this lineString as lineString.getCentroid(). But ...
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157 views

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

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

Calculating Centroids with Zonal Geometry in ArcGIS

I have a shapefile containing polygons. Each polygon is defined by its postal code. I want to calculate the centroid of each polygon using Zonal Geometry. Sadly, for some polygons there are no ...
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1answer
139 views

Shortest distance from polygon centroids to a line in QGIS

To get the distance of each polygon centroid from a line, I have tried the Distance to nearest hub algorithm from the Processing Toolbox. The distances I got from the algorithm did not seem correct, ...
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148 views

How to calculate a population weighted centroid using a raster and shape file in QGIS?

I am very new to QGIS so please help me with a step by step answer. I have a raster file with population count and a shape file based on a large population and shape file. I have successfully created ...
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2answers
67 views

How to get a set of all buildings of an OpenStreetMap section in form of single points / Multiple polygons as one point

The objective is to get a set of all buildings of an Open Street Map section in form of single points in a shapfile. I downloaded the section from osm. Imported the section into QGIS (and later ...
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31 views

Multiple Centroids within a dataset based on distance

Is there a way that we can find out the centroids of clusters within a dataset while differentiating one cluster from other based on distance not on any attribute value. The dataset is present in ...
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3answers
348 views

Combining different geometry types into same feature class?

I've searched the question in this blog. Maybe I don't use the right words but anyway my problem is not present in any post so I'll try to explain my question by opening a new one. I have a polygon ...
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1answer
58 views

Qgis creating point within complex shapes (with holes) [duplicate]

I'm looking for a tool to create a point in every polygon, that will be placed in the polygon. these are complex shapes with holes. the point must not put in those holes! the "plugin RealCentroid" ...
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1answer
168 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 ...
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1answer
623 views

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 ...
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360 views

What is Centroid of all lands of Earth?

May be my question is somehow ridiculous but I want to find the center point of all lands of the earth. What I have tried up to now is downloading shape file of all countries and polar parts of the ...
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404 views

Polygon to point conversion in ArcMap

I tried to convert polygons to point using Feature to Point under data management toolbox in arcGIS 10.2 (got it from uni. licensed). I got the point layer but it is not showing anything. I added X ...
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1answer
232 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 ...
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1answer
101 views

How to get projected centroids in QGIS?

I am trying to get a centroid for several polygons on a global scale, in a way that it would correctly represent the common centre of all the polygons, taking Earth's curvature into account. The ...
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1answer
1k views

How to calculate centroid of a polygon defined by a list of longitude/latitude points? [duplicate]

I've imported some polygons (ways) from OpenStreetMap and now want to calculate the centroids of them. For this purpose I wrote following code: final List<Point2D.Double> points = ...
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226 views

Locating the centroid (center of mass) of spherical polygons

I'm trying to work out how best to locate the centroid of an arbitrary shape draped over a unit sphere, with the input being ordered (clockwise or anti-cw) vertices for the shape boundary. The density ...
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2answers
173 views

How to obtain Census Tract Centroids when Bureau's web site unavailable?

Does anyone have the Census Bureau file of census tract centroid, for either 2000 or 2010 tracts? With the Bureau's web site shut down, the only available file is the EPA's, and it omits about 500 ...
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1answer
375 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 ...
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1answer
625 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?
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List of central coordinates for all countries?

I need a list of the central points 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) etc...
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1answer
81 views

How to convert polygons to centriods without losing attribute names?

I have a GeoJSON file of polygons and I need to convert it to centroids. Finding the centroid is very easy in QGIS. Problem My attribute names are very long and have a colon between them, e.g. ...
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328 views

How to use centroid option in Field Calculator in QGis

I want to use Centroid option in field calculator in QGis .How to access it?
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1answer
116 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 ...
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1answer
437 views

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 = ...
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1answer
89 views

Finding point in polygon

I want to calculate a point in a polygon, if the centriod falls inside the polygon it is what I want, but if it doesn't I would like it to be a visual center point. Essentially I want to do the ...
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806 views

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 ...
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1answer
98 views

Find the vertices of an ROI in XROI using IDL

I need to find the vertices of an ROI shape created in IDL's XROI, so that I can redraw the ROI on multiple images. I know you can find the centroid, area and perimeter with the GEOMETRY command, but ...
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722 views

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 ...
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3answers
5k 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 ...
2
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0answers
176 views

Centroid of the equator and a point

Suppose I already have a way to compute the centroids of different geometry types: Points (arithmetic mean of Cartesian coordinates). Linestrings (polylines) (weighted mean of segment mid-points in ...
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1answer
4k views

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 ...
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2answers
2k views

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 ...
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votes
1answer
2k views

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 ...
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2answers
2k views

Is it possible to extract Coordinates of Polygon Centroid in QGIS?

I have created polygon centroids using one of the "Geometry Tools" but I would like to extract the actual coordinates into Excel for further work. Is this possible?
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1answer
437 views

table of polygon centroids

Given a polygon layer, census tracts, how can I generate a table of centroid coordinates in QGIS, or add columns with the centroid coordinates or generate a new layer of polygon centroid points?
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1answer
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ArcGIS 10 — Polygon Centroid Options and Appropriateness (FeatureToPoint, Labels, etc)

I've found a couple of other Stack Exchange questions related to this, but just like the ArcGIS online help, they were not satisfying. For instance, How does ArcGIS calculate the "inside" ...
2
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3answers
3k views

Find polygon centroid with Python

I'm using ArcGIS 9.3 to find centroid of some polygon features. I'd like to do this in Python, but so far I can only find solutions with VBA. Can anyone provide some leads here?
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1answer
3k views

How to find polygons centroids? [duplicate]

Possible Duplicate: Get list of coordinates for points in a layer? Sorry for another basic question - my map is almost done but now my boss wants me to enter new outbreaks (that we don't ...
29
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1answer
9k views

How to find the center of geometry of an object?

Well it might be a simple question. Given a set of 2D or 3D points, the question is: How to find the center of geometry of an object? According to the following figure, the center of geometry ...
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3answers
13k views

How to get the coordinates in Lat/long from a point layer?

Sorry for asking this basic question, but I couldn't get the solution from the previous answers. I need to extract the Lat/long coordinates of the centroids of districts. My QGIS project SCR and the ...
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2answers
1k views

Formula to get polygon centroid

I need to compute the centroid position of an irregular polygon with lat and lon coordinates in Java. Which formula should I use to correctly compute a centroid?
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3answers
836 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 ...
9
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1answer
3k views

How does ArcGIS calculate the “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: Using Calculate Geometry on fields within the attribute table of the ...
6
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1answer
741 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 ...
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880 views

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

Heres what i want to achieve: i have a roading 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 ...