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## gettign teh area inside a polygon or territory

This is a discussion on gettign teh area inside a polygon or territory within the MapPoint Desktop Discussion forums, part of the Map Forums category; I am interested in gettign the area of a territory , state or polygon. I often have territories of very ...

1. Senior Member Black Belt
Join Date
Jul 2002
Posts
5,137

## gettign teh area inside a polygon or territory

I am interested in gettign the area of a territory , state or polygon.

I often have territories of very different sizes and these territories will have higher values inside teh territorty (sales for example) what I want is to beable to get sales densties.
any idea. I f I had the value fo the area I could get something like sales per sq mile or soemthing and be able to compare diferent size regions for potential.

2. Junior Member White Belt
Join Date
Jan 2003
Posts
8

## Area calculation

For calculating the surface area of a closed polygon there's a simple formula, that looks like:

For i = 1 to n
temp = temp + X[i] * (Y[i+1] - Y[i-1])
Next i
Area = temp / 2

(if i=1, then Y[i-1] = Y[n])
(if i=n, then Y[i+1] = Y[1])

However, this works for plane X,Y coordinates, not the geographic latitude and longitud that you can extract from MapPoint. Therefore you'll have to convert to plane coordinates first. I didn't work it out yet, but perhaps an approximation is good enough (as you'll know 1 degree of longitud at the equator is about 111 km, but less at higher latitud).

Greetings, Jack.

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