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 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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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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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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103 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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591 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
239 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
904 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
119 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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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
157 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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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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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 ...
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0answers
223 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
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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 ...
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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 ...
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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 ...
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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
486 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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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 ...
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3answers
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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
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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 ...
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1answer
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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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How to add Lat/long columns to a point layer which is not in WGS84?

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 ...
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2answers
2k 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
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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 ...
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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 ...
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1answer
941 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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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 ...
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3answers
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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 ...
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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 ...
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6answers
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Is it possible to query a MySQL database using the results from map.getBounds() with Google Maps API v3?

I have a MySQL database that contains a large number of polygons, one for each district on a map. They are all quite complicated and it's unrealistic to simply load them all at once. I've looked into ...
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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 ...
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Where can I obtain an up-to-date list of US ZIP Codes with Latitude and Longitude Geocodes?

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 ...
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2answers
487 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 ...