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I have only lengths for the sides of an irregular polygon, can anyone tell me how I can measure the area of the polygon? Remember only lengths of all the sides , no angles or coordinates.

Few forums mention about trangulation of the polygon etc But I only have side lengths.

Does anybody has any feedback?

Thanks.

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migrated from meta.gis.stackexchange.com Mar 7 '12 at 14:25

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Some polygons have four sides of length 1. Such a polygon can have various shapes, from a square down to a long thin needle of length almost 2. Its area will range from 1 down to 0. This shows why the side lengths of any polygon of four or more sides usually do not determine its area. Therefore a formula or calculation of the type you seek does not exist. –  whuber Mar 7 '12 at 14:27
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Another example: a concave figure (smaller area) vs convex figure (larger area), each with same perimeter. –  sgillies Mar 7 '12 at 16:41
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1 Answer 1

As Whuber has mentioned in his comment, a four sided polygon is -mathematically speaking- constrained by 5 properties at a minimum. So If you have just the four side lenghts, you do not have one unique polygon. Hence you can't find its area.

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My scenario is- user roughly digitizes the irregular polygon on the openlayers map and enters the exact lengths for each side of the polygon and I wanted the area to be calculated. Since everybody has mentioned that it is not possible to calculate area based on the side lengths, can the digitized polygon sides be adjusted according to the lengths entered and bring the polygon roughly to the nearest to what is supposed to be a correct polygon? Is it something possible in POSTGIS or SQL Server 2008? I think it is possible in Geomedia. –  user5958 Mar 8 '12 at 11:07
    
The digitized points should have coordinates, which can then be used to calculate the area of the polygon. The problem with using just lengths is that angles are needed also. The points used to define the polygon can also be used to get the angles. There is a standard formula for calculating the area. mathworld.wolfram.com/PolygonArea.html –  mhoran_psprep Mar 12 '12 at 12:42
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