How to collect all polygons to MBR ?

Question

I am new to SQL spatial querys.

I would like to know if i can write a query that automatically gives me the MBR of all polygons that are positioned in the same area without knowing that area in first place

Consider it as a paragraph of words on a sheet of paper, i want to select only those polygons ( rectangle of each word) where the left, right, below and top neigbours ( other words) are within certain x,y distance ?

I am an absolute beginner :)

Thx !

Answer 1

Hi,

So you're trying to group a set of source polygons together into a number of discrete clusters, where each cluster contains a set of "close together" features (i.e. those that are "positioned in the same area")? Is that right?

If so, it sounds like k-means clustering might be what you're after: http://en.wikipedia.org/wiki/K-means_clustering.

SQL Server has no function to perform clustering out-of-the-box, but it's relatively easy to write a SQLCLR procedure that will do this. <plug>In fact, I demonstrate a k-means clustering algorithm in Chapter 13 of Pro Spatial with SQL Server 2012. That example uses a set of point data, but you could do the same by applying it to the centroid of each Polygon</plug>

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twitter: @alastaira blog: http://alastaira.wordpress.com/

Answer 2

You are absolutely right ! I was hoping that SQL had an out of the box solution :)

Do you have a script for this ?

Thx !

Answer 3

Yes - let me just check with the publishers whether it's ok to reproduce.

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twitter: @alastaira blog: http://alastaira.wordpress.com/

Answer 4

It's ok , I have bought the ebook !

Grtz,

Tom