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How draw circle into circle or "donut" ?

Unanswered How draw circle into circle or "donut" ?

  • Saturday, February 25, 2012 3:32 AM
     
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    Hello,

    Im a beginner in spatial data. So, I know how to draw complex polygone with hole like 

    DECLARE @g GEOMETRY
SET @g = 'POLYGON((0 0, 0 10, 10 10, 10 0, 0 0), (1 1, 4 5, 4 1, 1 1))'
SELECT @g

    but how to draw circle into circle like donut ??

    see http://www.geocodezip.com/v3_polygon_example_donut.html

     

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  • Saturday, February 25, 2012 7:58 AM
    Answerer
     
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    You declare it exactly the same way - with the exterior ring (the outside of the circle) listed first, and then the inner ring (the "hole") listed second.

    SQL Server 2008/R2 doesn't support truly curved geometries (but then again neither does the Google Maps example you've given). You can create approximate "circular" n-sided polygons around a point using STBuffer(), like this:

    DECLARE @Centre geography = 'POINT(151.2 -33.9)'; --Sydney, Australia
DECLARE @RadiusOfCircle float = 150000; --150km
DECLARE @RadiusOfHole float = 70000;  --70km

-- Create a Doughnut polygon by subtracting hole from the circle
SELECT @Centre.STBuffer(@RadiusOfCircle).STDifference(@Centre.STBuffer(@RadiusOfHole));

    Or, if you're using SQL Server 2012, you can use the BufferWithCurves() method to create CurvePolygon of the same.

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