On Oct 8, 7:27*pm, cavelamb wrote:
DoN. Nichols wrote:
On 2009-10-08, Rich Grise wrote:
On Wed, 07 Oct 2009 20:23:18 -0600, SteveB wrote:
"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
68.3.70...
fired this volley in news:656dee88-c74d-4919-a95a-
:

You can't do it just by
measuring the perimeter unless it's a regular figure, circle,
semicircle, triangle, hexagon, or whatever.

WRONG! *Check out what planimeters do! *(geeesh!)
I Googled planimeter, and came up with
http://en.wikipedia.org/wiki/Planimeter
So did I - and for a swimming pool, wouldn't that need one BIG HONKING
planimeter?

* *Or a nice aerial or satellite view from directly overhead and a
measurement between two known locations to calculate a scale factor.
Find the view, print it out, measure the distance between the two known
locations on the printout and the real world, then run the planimeter
around it and calculate the full scale area from the indicated area and
the scale factor.

* *I've got a nice old planimeter which I bought at a hamfest about
ten or fifteen years ago.

* *How much accuracy is needed for this project?

* *Enjoy,
* * * * * *DoN.

Not that much, apparently.

SteveB's (OP) solution was to measure across the pool in several places,
average the widths and multiply by the length.

Close enough for non-financial government work.-

A potentially accurate method is to divide the central area into
triangles and use Heron's formula in a spreadsheet:
http://mste.illinois.edu/dildine/heron/triarea.html

Assume the ends are semicircles and start the triangles one radius in
from the ends. The chord errors on the convex and concave sides may
partly compensate for each other if the curvatures are similar.

jsw