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 ...

learn more… | top users | synonyms

5
votes
1answer
131 views

How to connect centroids of lines sharing the same intersection in QGIS?

I'm looking for a big help to accomplish the following task: I have this street network of the center of Turin (IT), composed by lines representing streets, and black points representing ...
1
vote
1answer
43 views

How do I find the centroid of each patch in a raster?

I am trying to get the centroid of a several areas in a large raster data set. The output needs to be raster format, with one pixel representing the center of each patch, in the same resolution as ...
1
vote
1answer
111 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 ...
5
votes
0answers
985 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 ...
2
votes
0answers
34 views

Finding centroids for icosahedral gnomonic projection?

I've been trying to create an icosahedral gnomonic projection, like this example by Jason Davies or this one (the Fisher projection). The method that I initially used was using the centroid of each ...
2
votes
0answers
202 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 ...
1
vote
0answers
87 views

Finding census block with highest pop. value within the census tract

In QGIS, I'm trying to plot a centroid of only the census block with the highest population within each census tract. So there should only be one point per tract- that of the block with the greatest ...
1
vote
0answers
39 views

Postgis routes diagram point-to-point

I have a set of centroids to which are related a set of points characterized by linename. The table with the points contains these fields: id ¦ linename ¦ lat ¦ lon¦ I would like to make a diagram ...
1
vote
0answers
70 views

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 ...
1
vote
0answers
318 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 ...
0
votes
0answers
13 views

Calculating population statistics for postcode centroids

Perhaps this isn't really specifically a GIS question, but I've been using ArcMap to measure distances from the access points of green spaces in Bristol to postcode centroids and would like to use ...
0
votes
0answers
24 views

how to assign the same centroid to polygons grouped by ID , R

I have a SpatialPolygonDataFrame object from a shapefile of different zip codes in New York state, many zip codes are represented by several polygons( for different reasons) so I want to assign the ...
0
votes
0answers
28 views

Color polygon centroid according to attribute value in GRASS

I have many polygons in GRASS and want to color them according to their T-value. I can use v.colors and define a color table. That works fine when I plot the areas of the polygons. However, I would ...
0
votes
0answers
56 views

Problem with MySQL CENTROID() in 5.6

We're testing out an upgrade to MySQL 5.6 to take advantage of it's enhanced GIS functionality, and we ran into this problem: SET @mpoly = GeomFromText('MULTIPOLYGON(((0 0,0 2,2 2,2 0,0 0)),((0 4,0 ...
0
votes
0answers
57 views

Routes through centroids and array functions

I have a table stopcentroids4 like in figure with the following fields: gid, routes, geom and i want to draw a line for each route that runs through centroids. In my code there is a mistake. ...
0
votes
0answers
307 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 ...