topic Manual creation of polygon that crosses dateline in ArcObjects SDK Questions

Manual creation of polygon that crosses dateline

TimB — Wed, 07 Aug 2013 20:01:05 GMT

I am having issues manually creating a polygon that crosses the dateline (long=180). My x coordinate goes from 178, 179, 180, -179, -178, etc. Anyway, can anyone give me some guidance?

I am using ArcEngine 10.0 to do so. I know how to create the polygon via code, but it is the dateline issue I am having problems with. Once it crosses to -179, there is a straight line across the screen. I am familiar with the geodesify option (for polylines) and I saw there is one for elipses, but the polygon I am creating is not an elipse.

Re: Manual creation of polygon that crosses dateline

AlexanderGray — Thu, 08 Aug 2013 11:56:07 GMT

I take it you are using a geographic coordinate system. Those are problematic since the 180 line is considered the zero X axis. One way to get around the problem is to add a line at 180 and make the polygon a two part polygon with a part on either side of the 180 line. The other solution is to change the coordinate system to something that will handle the 180 line better. In our application our polygons are north of 45 and most near the pole so we switched to a polar stereographic projected coordinate system.

Re: Manual creation of polygon that crosses dateline

TimB — Fri, 09 Aug 2013 11:54:29 GMT

Alexander,
Thanks for the reply. That sounds like the best way (cutting at 180) to do it for us. We are using GCS and also these polygons are global coverages that differ, so there will always need to be a break somewhere, so I don't think using a different projection would work. I do like you break idea, though. In fact, now that I think about it, it think that is what ArcGIS might do when creating a buffer that crosses the dateline. Thanks again!