CODEWITHSUNDEEP
sql-server-2008-r2spatialgeography
Sylvain C.
Sylvain C.

Reputation: 1073

SQL Server 2008 R2 large polygons along latitude

Working on the Pacific Ocean, i am dealing with huge polygons covering the whole area. Some of them are quite simple and are defined by 4 points in my shapefile.

However, when i import them into SQL server 2008 r2 as new geographies, due to the shape of the earth, i end up with curved lines while I would like the North and South boundaries to stick to some specific latitudes: for example, the north boundaries should follow the 30N latitude from 120E to 120W.

How can i force my polygons to follow the latitudes? Converting them as geometry could have been an option but since i will need to do some length and area calculations, i need to keep them as geography. Do i need to add additional vertices along my boundaries to force the polygon to stay on a specific latitude? What should be the interval between each vertex?

Thanks for your help

Sylvain

Upvotes: 1

Views: 51

Answers (1)

Jon Bellamy
Jon Bellamy

Reputation: 3373

You have already answered this yourself. Long distances between latitude coordinates will create curved lines to match the Earth's curvature. Therefore if you need to "anchor" them along a specific latitude you will need to manually insert points. As for the interval, there's no right or wrong, a little experimentation here (and considering how "anal" you want to be about it hugging the line) will give you the result you desire. 1 coordinate per degree should do it, might even be a little overkill.

That said, I do question why you would want to anchor them to create a projected "straight" line as this will skew the results of length and area calculations, the bigger the polygon, the bigger the skew.

Upvotes: 1

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