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Re: Already written function to find if a point is within a rectangle? [message #79398 is a reply to message #79347]

Thu, 23 February 2012 01:34

Craig Markwardt
Messages: 1869
Registered: November 1996

Senior Member

On Feb 22, 10:25 pm, Jacare Omoplata <walkeystal...@gmail.com> wrote:
>>>> So I need a way to find out if a point ( position of a star ) is
>>>> within a rectangle ( image boundary ). The rectangle edges are not
>>>> strictly horizontal or vertical.
>
>>> You talk about coordinates in RA and dec. So are the images really
>>> rectangular? It seems to me that the real problem is that you need to
>>> deal with spherical geometry.
>
>> Not only that, but an "image boundary" will be projection-dependent
>> [*]. For small images it probably won't matter much, but there will
>> always be an edge case that gets you later.
>
> I'm thinking of making polygons with a large number of edges, instead
> of rectangles, with every data point at the edge of a FITS file as a
> vertex. That would minimize the projection error, right?

That helps. Special care is probably need around the poles though.

Craig

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[Message index]

		Already written function to find if a point is within a rectangle? By: Jacare Omoplata on Mon, 20 February 2012 13:29
		Re: Already written function to find if a point is within a rectangle? By: Jacare Omoplata on Fri, 24 February 2012 22:33
		Re: Already written function to find if a point is within a rectangle? By: suruchi on Sat, 18 May 2013 21:19
		Re: Already written function to find if a point is within a rectangle? By: JDS on Fri, 24 February 2012 14:00
		Re: Already written function to find if a point is within a rectangle? By: Jacare Omoplata on Fri, 24 February 2012 10:48
		Re: Already written function to find if a point is within a rectangle? By: penteado on Thu, 23 February 2012 11:13
		Re: Already written function to find if a point is within a rectangle? By: Greg Hennessy on Thu, 23 February 2012 10:05
		Re: Already written function to find if a point is within a rectangle? By: Craig Markwardt on Thu, 23 February 2012 01:34

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