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I have Area value in sq-feet and centroid point.Based on these values,I want to draw the polygon.Is there any formula for this.Thanks in advance.
How to get the polygon coordinates based on Area and Centroid
Date: May 13, 2010 11:24PM

I have Area value in sq-feet and centroid point.Based on these values,I want to draw the polygon.Is there any formula for this.Thanks in advance.

Re: How to get the polygon coordinates based on Area and Centroid
Posted by: pmeems ()
Date: May 17, 2010 02:04AM

You can use the buffer method for it.
Make sure your projection is in sq-feet as well, create a new polygon shapefile, create the buffer around the centroid and add it to the new shapefile.

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Paul

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---
Paul Meems
The Netherlands
[www.bontepaarden.nl]
Release manager, configuration manager and
forum moderator of MapWindow GIS

Owner of MapWindow.nl - Support for
Dutch speaking users: www.mapwindow.nl

*******
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Re: How to get the polygon coordinates based on Area and Centroid
Date: May 17, 2010 06:39AM

If i want to expand or shrink a polygon to given area,then what is distance value in below method:
MapWinGeoProc.SpatialOperations.BufferPolygon().
I mean that how to calculate the distance in order to get the polygon based on GivenArea.

Re: How to get the polygon coordinates based on Area and Centroid
Posted by: Sergei ()
Date: May 17, 2010 06:57AM

You could use:

Area = pi*Radius^2 for a circle;
Area = Side^2 for a square.

Re: How to get the polygon coordinates based on Area and Centroid
Date: May 17, 2010 11:28PM

If i want to expand or shrink a polygon to given area,then what is distance value in below method:
MapWinGeoProc.SpatialOperations.BufferPolygon(shape,distance,ResultantShape).
I mean that how to calculate the distance in order to get the polygon withGivenArea.
Pls send me answer.Its very urgent.

Re: How to get the polygon coordinates based on Area and Centroid
Posted by: pmeems ()
Date: May 18, 2010 12:14AM

The distance is in map units. So in meters, feet, degrees, how ever your projection is.

I would suggest using resultingShape = sh.Buffer(distance)
It is faster and more robust.

This summer we will update mwGeoProc.

Thanks,

Paul

--
Don't forget to read the new documentation: www.mapwindow.org/documentation/mapwingis4.8

tinyurl.com/mwMonthly 32-Bit
tinyurl.com/mwMonthlyx64 64-Bit

---
Paul Meems
The Netherlands
[www.bontepaarden.nl]
Release manager, configuration manager and
forum moderator of MapWindow GIS

Owner of MapWindow.nl - Support for
Dutch speaking users: www.mapwindow.nl

*******
Everything I say or write is my personal opinion and
not the opinion of the company I work for.
*******

Re: How to get the polygon coordinates based on Area and Centroid
Date: May 18, 2010 02:48AM

suppose i have a Polygon with area of 2000 sq-feets.Next,I want to get the output as shrinking same polygon to an area of 900 sq-feets.

for shrinking polygon,I will use BUFFER method with appoximate distance value.But the Resultant shape will not have an area of 900 sq-feets.So,now to get the Resultant shape with an area of 900 sq-feets, how much distance value should i pass to this method sh.Buffer(distance).Is there any relation between Polygon area and distance?
I think u will catch my doubt.

Re: How to get the polygon coordinates based on Area and Centroid
Posted by: pmeems ()
Date: May 19, 2010 12:58AM

I see now. I didn't understand the result was in square feet.

I think you should make a loop, decreasing the buffer until you get a resulting area of 900 sq-feet.

Or if the input shape is a regular shape: circle, ellipse, rectangle, etc. you can use Sergei's calculation.

Hope it helps,

Paul

--
Don't forget to read the new documentation: www.mapwindow.org/documentation/mapwingis4.8

tinyurl.com/mwMonthly 32-Bit
tinyurl.com/mwMonthlyx64 64-Bit

---
Paul Meems
The Netherlands
[www.bontepaarden.nl]
Release manager, configuration manager and
forum moderator of MapWindow GIS

Owner of MapWindow.nl - Support for
Dutch speaking users: www.mapwindow.nl

*******
Everything I say or write is my personal opinion and
not the opinion of the company I work for.
*******

Re: How to get the polygon coordinates based on Area and Centroid
Date: May 19, 2010 04:49AM

If i use loop,then for how many iterations,i will get the exact given area of irregular polygon.
I think,this way of logic would be some what critical.Because if i apply this type of logic for all the shapes in shapefile,then it will get so much of time to get the output.Is there any idea or algorithms othen than loop?

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