[R-sig-Geo] Area of Spatial Domain

[Michael Sumner]

In general, no you cannot say that this would be correct. It depends
on where and how extensive the region is, so if you can tell us that I
could put together something to show how valid it would be. You should
reproject to a local equal area projection and then it's going to be
valid, but even then you'd want to do some checks, depending, again on
where and for what.

Within 100s of kilometres is probably ok, but then it depends on the
latitude you are at, *and* which zone you are using (it's easy to get
this wrong believe it or not and UTM is one of those *defaults* that
can cause problems because it is a default - there's no good technical
reason to use it if you can help it. Each zone is only 6 degrees wide,
and if you are near a transition it's better to use a local one rather
than a standard zone, which again begs the question of why it would be
used).

This also has relevance downstream if you are using a projection
incorrectly so it's worth understanding well. There are plenty of
resources on this out there.

Cheers, Mike.





It's safest to reproject to an appropriate equal area projection, and then

On Tue, Jun 25, 2013 at 6:38 AM, Moshood Agba Bakare <bakare at ualberta.ca> wrote:
> Dear All,
> Am I right to calculate the spatial region or domain by multiplying the
> range of easting and northing coordinates? That is, I intend to find the
> difference between the minimum and maximum values in meters for each of the
> UTM coordinates (easting and northing) and get the product of the range as
> area of spatial domain in square meters.
>
> Please let me know if I am right or wrong.
>
> Thank you.
> Moshood
>
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>
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-- 
Michael Sumner
Hobart, Australia
e-mail: mdsumner at gmail.com