Trying to calculate acreage/area from polygon array loaded from JSON result of map service query and running into issue with geometries that contain "holes". From what I know, the first list of coordinate pairs (index 0) is the "outer" polygon, then all other coordinate pairs would be the interior rings. This is easiest enough to setup a condition to identify and calculate total area. For example area of a polygon with two interior rings could be determined by:
ring[0] area - ring[1] area - ring[2] area = total area
Got it. However, what if the polygon consists of 1 ring with interior rings and a ring coincident. That is, there are what looks like 2 polygons coincident to each other but one of them contains holes.
How do I come up with the total area in this case? Example below shows 2 coincident polygons, 1 with holes that needs to have the area of interior rings subtracted from the overall ring, while the coincident polygon only has 1 ring that must be added to the total area.
Edit: to simplify my question, how do I arrive at the count of 2 rings (area of 1 "island" ring, area 1 outer ring - total area of 7 interior rings)
Here's the json for the rings in picture:
{
"rings" : [
[
[
-8960520,
3141929
],
[
-8960482,
3141916
],
[
-8960381,
3141979
],
[
-8960297,
3142183
],
[
-8960220,
3142291
],
[
-8960267,
3142363
],
[
-8959212,
3142329
],
[
-8959216,
3140075
],
[
-8960546,
3141806
],
[
-8960599,
3141897
],
[
-8960692,
3142376
],
[
-8960637,
3142374
],
[
-8960622,
3142346
],
[
-8960608,
3142230
],
[
-8960516,
3142015
],
[
-8960520,
3141929
]
],
[
[
-8960049,
3141823
],
[
-8960001,
3141812
],
[
-8959983,
3141860
],
[
-8960017,
3141990
],
[
-8960058,
3142011
],
[
-8960083,
3141987
],
[
-8960049,
3141823
]
],
[
[
-8959472,
3141918
],
[
-8959391,
3141908
],
[
-8959340,
3141951
],
[
-8959320,
3142025
],
[
-8959325,
3142112
],
[
-8959387,
3142168
],
[
-8959484,
3142163
],
[
-8959513,
3142124
],
[
-8959472,
3141918
]
],
[
[
-8959828,
3142151
],
[
-8959808,
3142211
],
[
-8959826,
3142302
],
[
-8959875,
3142344
],
[
-8959943,
3142320
],
[
-8959986,
3142228
],
[
-8959959,
3142148
],
[
-8959927,
3142120
],
[
-8959858,
3142113
],
[
-8959828,
3142151
]
],
[
[
-8959663,
3141625
],
[
-8959585,
3141438
],
[
-8959535,
3141389
],
[
-8959428,
3141379
],
[
-8959399,
3141424
],
[
-8959384,
3141551
],
[
-8959497,
3141761
],
[
-8959571,
3141760
],
[
-8959663,
3141625
]
],
[
[
-8959960,
3141599
],
[
-8960028,
3141615
],
[
-8960074,
3141591
],
[
-8960098,
3141499
],
[
-8960095,
3141436
],
[
-8960049,
3141324
],
[
-8960008,
3141263
],
[
-8959800,
3141169
],
[
-8959793,
3141018
],
[
-8959741,
3140928
],
[
-8959722,
3140834
],
[
-8959630,
3140750
],
[
-8959570,
3140741
],
[
-8959528,
3140782
],
[
-8959542,
3140877
],
[
-8959601,
3141041
],
[
-8959719,
3141213
],
[
-8959733,
3141325
],
[
-8959797,
3141385
],
[
-8959960,
3141599
]
],
[
[
-8959346,
3140751
],
[
-8959388,
3140703
],
[
-8959379,
3140596
],
[
-8959479,
3140586
],
[
-8959518,
3140560
],
[
-8959514,
3140503
],
[
-8959403,
3140475
],
[
-8959393,
3140355
],
[
-8959278,
3140327
],
[
-8959249,
3140351
],
[
-8959237,
3140406
],
[
-8959333,
3140479
],
[
-8959343,
3140579
],
[
-8959291,
3140665
],
[
-8959296,
3140732
],
[
-8959346,
3140751
]
],
[
[
-8960421.4573999997,
3141207.5951999985
],
[
-8960651.4805999994,
3140355.0742999986
],
[
-8960730.3613000009,
3140457.7377999984
],
[
-8960501.8148999996,
3141210.1849000007
],
[
-8960421.4573999997,
3141207.5951999985
]
]
]
}
