SQL Server Geography - Find International Dateline and Equator

Question

In SQL Server, I want to find if geography intersects/crosses the international dateline and equator.

I thought of the below logic but am not sure if it is the right way of doing this.

• Geography crossing international date line: if the coordinates of the international date line fall within the given coordinates then it seems to cross the dateline

• Geography crossing the equator: if any of latitude from the given coordinate is <= 0 then it seems to cross the equator

Any help is highly appreciated.

Answer 1

What I'd do is come up with linestrings that represent the Equator and International Dateline (respectively). From there, you can use STIntersects() against your geography data to test for intersection.

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Addendum - here are naïve definitions of the equator and International Date Line (IDL). The equator works around what appears to be a technical limitation in SQL Server's geography implementation regarding antipodes while the IDL uses the simple but incorrect definition of "longitude -180°".

DECLARE 
    @e GEOGRAPHY = geography::STMLineFromText('MULTILINESTRING ((-179.9999 0, 0 0), (0 0, 179.9999 0))', 4326),
    @idl GEOGRAPHY = geography::STMLineFromText('MULTILINESTRING ((-180 0, -180 90), (-180 0, -180 -90))', 4326);