PolygonArea ( xlist ; ylist )

Calculate area of a polygon from array of XY coordinates

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Jeremiah Small - Show more from this author
Soliant Consulting, Inc.
https://www.soliantconsulting.com

Sample input:

PolygonArea ( List ( 0;3;0 ) ; List ( 0;0;3 ) )

Sample output:

4.5

Function definition: (Copy & paste into FileMaker's Edit Custom Function window)

//20060806 jsmall@soliantconsulting.com
//purpose: calculates area of polygon using Double Meridian Distance
//dependency: PolygonAreaHelper
//key: Lat is Latitude; Dep is Departure

If ( ValueCount ( xlist )  ≥ 3 and ValueCount ( xlist ) = ValueCount ( ylist ) ;

Let ([
Lat = MiddleValues ( ylist ; 2 ; 1 ) - MiddleValues ( ylist ; 1 ; 1 ) ;
Dep = MiddleValues ( xlist ; 2 ; 1 ) - MiddleValues ( xlist ; 1 ; 1 ) ;
DMD = Dep ;
DArea = Lat * DMD ;
TotalDArea = DArea + PolygonAreaHelper ( xlist ; ylist ; Dep ; DMD ; 2 ; ValueCount ( xlist ) )
];

Abs ( TotalDArea ) / 2

) ;//endLet

"Lists must contain same number of values, minimum 3."

)//endIf

Calculate the area of a polygon from an arbitrary number of xy coordinates. It uses an old surveying technique called Double Meridian Distance.

Requires helper function: PolygonAreaHelper

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Note: these functions are not guaranteed or supported by BrianDunning.com. Please contact the individual developer with any questions or problems.

PolygonArea ( xlist ; ylist )

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