Lugnut,

I see the same problems in your attempt at analysis that Joe Shmoe sees.
There is no "representative ground area" when you're doing prism plots. Like
Joe says, it depends on the level of error you want to achieve, what type of
sample your after, etc. You need to decide what "n" you need to represent
"N" based on a number of specifics.

If you're looking for a representative plot, why not do fixed plots? If you use

a 1/10 acre plot, it will be 1 chain x 1 chain square, which is very simple
to set up, and the statistics are much more easier to calculate.

Typically, the only reason you would use a prism is to estimate square foot
basal area, while sampling trees for volume. It can give you an estimate of
trees/acre, but it will always steer you wrong because larger trees are certain
to overrepresent themselves vs. saplings. Stick with the square, you'd be much
better off!

-Geoff Kegerreis

www.timberlineforestry.com

LugNut wrote:

Where I was froming come is that I was always told to use 0.004 hectare
to represent the amount of ground area in a prism sweep as a rough and dirty
number for a 2 BAF (metric) prism. I know that it will vary based on stem
diameters but I was wondering what the same rough and dirty number was for a
10 BAF Imperial.

Cheers

LugNut

"Joe Shmoe" wrote in message
...
LugNut wrote:

I'm not quite sure what you're asking. Acceptable sample size (ie number
of
plots required to achieve a required Standard Error) is not directly
related to the prism size. Ideally, you wouldn't choose a prism until you
saw the size and number of stems in a stand.

And as for ground area represented by a prism, I really don't understand
the question. The plot radius of each tree is a function of the BAF and
the tree's diameter.

So, I guess I'm no help, I just felt like babbling

Joe


Hello

I am doing a point-in-polygon GIS analysis and need to know what would
be
the acceptable sample size (ground area) represented by a 10 BAF prism
(10
ft2 per acre) at each point.

Regards

LugNut