Systems 22(3):205-221.
Denis
[EMAIL PROTECTED] wrote: -
To: [EMAIL PROTECTED]
From: Tim Keitt <[EMAIL PROTECTED]>
Sent by: [EMAIL PROTECTED]
Date: 02.06.2006 08:56
cc: r-sig-geo@stat.math.ethz.ch
Subject: Re: [R-sig-Geo] Computing polygon area with decimal degree
coordinates
Ah, that i
Ah, that is very useful. I'd always assumed the hard part is computing the
area of the triangles on the surface of a sphere/elipse, but perhaps that is
not so hard after all. Anyone have a reference to some simple formulas? The
other question is how much error is introduced if one computes areas af
I may be misunderstanding the discussion about polygon area,
but:
At the risk of restating a well-known fact, it's not mathematically complicated
to compute the area of a polygonal region (consisting of one or more separate
regions bounded by polygons, possibly including holes) on any oriented
t
Yes, agreed... I realized that after having formulated the question and
posted it
Tim Keitt a écrit :
> Do you mean the flat-plane area or the area projected onto the surface
> of the ellipsoid? In either case, the computation is likely
> non-trivial. It makes much more sense to project to
Do you mean the flat-plane area or the area projected onto the surface of
the ellipsoid? In either case, the computation is likely non-trivial. It
makes much more sense to project to UTM and do the calculation there.
THK
On 5/31/06, Patrick Giraudoux <[EMAIL PROTECTED]> wrote:
>
> Dear Listers,
>
On Wed, 31 May 2006, Patrick Giraudoux wrote:
> Well, thinking about it, I realize this question was a bit weird/silly
> in the real world... Decimal degree coordinates does not tell us
> anything about the ellipsoid/datum they refer to and this must be done
> within a CRS framework. If we want
Well, thinking about it, I realize this question was a bit weird/silly
in the real world... Decimal degree coordinates does not tell us
anything about the ellipsoid/datum they refer to and this must be done
within a CRS framework. If we want a reasonable precision on small
areas, sound mathemat
On Wed, 31 May 2006, Patrick Giraudoux wrote:
> Dear Listers,
>
> The function areapl() of the package splancs computes polygon areas in
> the coordinate units. This means in square meters when using UTM or
> Lambert projections but in "square degrees" when using longlat degrees.
>
> Does any
Dear Listers,
The function areapl() of the package splancs computes polygon areas in
the coordinate units. This means in square meters when using UTM or
Lambert projections but in "square degrees" when using longlat degrees.
Does anybody knows a R function (or an algorithm) to compute the area
