Most of the time, software treats the world like a 2D surface, usually stretched between -180º to +180º.
That works just fine, most of the time. Unless you live in New Zealand, Fiji or Alaska, where data regularly crosses that magical edge-of-the-world line (the 'antimeridian' - often confused with the International Date Line.)
In most cases, if a geometry crosses past +180º, it will 'wrap' back to -180º. Software that doesn't carefully handle this can cause headaches. Results can include rendering artifacts, invalid geometries, incorrect extents, bad 'cropping' of geometries, and confusing failures when doing intersections or transforms.
At Koordinates we deal with a diverse range of data in different projections, from a range of sources and formats. Lots of it straddles the antimeridian.
Perhaps because of our location in New Zealand, or because we deal with such a diverse range of data, we have to tackle lots of antimeridian problems that we can't find existing solutions to.
Not only does our software have to render data correctly on our websites, but it must be able to be projected into a number of different projections. This means that, even for data sourced from projections that don't have an antimeridian, we have to be able to handle it in an antimeridian-aware way.
In this talk, we'll discuss validation, geometry winding orders, WSEN extents and geography types. Then I'll showcase just a few of the (many) problems we've had with antimeridian geometries, and show some approaches for dealing with them.