Geometry union at antimeridian

Question

Hi all,

I have to union many extents all over the globe, including antimeridian (180th meridian) on both sides and crossing.

I cannot get to have extents on both sides of 180th meridian to merge :

https://codepen.io/Chris_Siveco/pen/JjxvpvJ?editors=1000

Only one side extents are merging. The one that is crossing 180th meridian is merging ok, and the one on the left also. But not the one on the right.

Is there a way to achieve this ?

Regards

JoelBennett · Accepted Answer

It is because on line 73. ext1 and ext3 do not intersect numerically speaking. That is, before the call to union, here is the state of things: ext1: (150, 50) -> (210, 80) ext3: (-175, 55) -> (-120, 65) As you can see, if you put this on a simple cartesian plane, they won't intersect. You can add some functionality to adjust the geometries one rotation around the world to the east or west to get what you're looking for like so: Intro to graphics | Sample | ArcGIS Maps SDK for JavaScript 4.28

Basically, the unionGeometries function was added, and the "extN" objects were created as full-on Extent objects to make this work. Note this only works if geometries are offset by no more than one rotation.