Madison,
My algorithm will produce A rotated rectangle, but not necessarily
THE minimum bounding rectangle. My focus was on finding the length of a
polygon, then the width perpendicular to that length (and my algorithm
is ok for that). JTS's getMinimumRectangle is the approach to use for a
rotated MBR. Think of a square polygon; my approach will result in a
larger square rotated 45 degrees from the original, whereas JTS will
produce a square of the same size and orientation as the original (as
would be expected for a rotated MBR).
Sorry for the misdirection...
Best Regards,
Brent Fraser
On 6/19/2012 3:42 AM, Madison Shaw wrote:
Thanks Martin - Ill have a look at JTS - otherwise I think I will be
implemeting it based on the steps Brent mentions.
I believe ArcGIS 10 has a set of tool to create them as well - but
requires an info license.
Thanks everyone for the help :)
Madison
On 19 June 2012 04:39, Martin Davis <mtncl...@telus.net> wrote:
JTS has a class for computing a Minimum Bounding Rectangle:
http://tsusiatsoftware.net/jts/javadoc/com/vividsolutions/jts/algorithm/MinimumDiameter.html
This may be in GEOS as well.
On 6/18/2012 9:36 AM, Brent Fraser wrote:
Madison,
I went looking a few months ago, but could find nothing. I wrote some
PHP to:
1. Find the length of the polygon (vertices farthest apart)
2. Find the width (based on vertices farthest from length line)
3. Build bounding box using length (with angle of the the length line)
and the width
I'm still pondering the result when the input polygon is a square...
But there should really be something like a "ST_ExtentRotated" or
"ST_RotatedBBox" function in PostGIS.
Best Regards,
Brent Fraser
On 6/15/2012 2:03 PM, Madison Shaw wrote:
Hi,
I was wondering if any one could possibly offer some advice.
I am wanting to calculate the area for a minimum bounding rectangle
for individual polygon features. I know I can use st_envelope or
st_extent along with st_area but this doesn't quite give me the
results I am after.
For example if the polygon was already a rectangle but was orientated
on an angle the bounding box area is much larger than the area of the
original rectangle, whereas I would like it to be the same value. I
suppose what I am after is a convex hull but as a rectangle. Is this
possible?
Any help is greatly appreciated.
Cheers
Madison
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