Using OGC functions in SQL Server 2008 part 3

It’s been a while since I last tried to do anything with the spatial features in SQL Server 2008. My next plan was to query the database to see which postcodes were in a particular county. To do this I got hold of the boundary data for some counties using the OpenSpace API. I just added one county, the one and only Lancashire, with the following code.

INSERT INTO CountyBoundaries (County, Boundary) VALUES ('Lancashire', 
geometry::STPolyFromText('POLYGON((335390.6 402509.3,335318.8 405919.1,337285.8 405717.9,341638.1 403012.7,341198.7 401158.3,

345355.3 399036.6,348231.1 404146.9,349111.4 402150.3,351662.6 402905.5,353409.1 407181.8,352474 409073.9,354484.8 412190.4,

358109.6 412599.6,358670 410970.3,360670.3 412859.2,362419.8 411151.7,366280.6 414615.7,364921.9 418843.3,366064.7 421813,

363060.8 427981.2,363748.5 429031.4,369403 431708.6,372966.5 423266.5,375369.8 421263.6,375568.6 419018,379162.2 417655.1,

380342.3 418953.7,382117.1 413139.9,383850.1 418586.1,385712 419187.4,387839.3 415759.4,389429.8 416106,390432.6 420649.6,

388662.6 425190.8,391447.8 428359.4,392703.4 434383.5,396065.9 436596.5,397063 439322.3,394185.1 441332.3,392652.8 446613.3,

388130.5 448821.7,387988.3 450699.5,387239.2 452627.7,385286.7 451690.4,384991.7 453964.6,380792.9 453190.5,379173.9 455357.1,

376997.3 455460,377844.2 457098.1,375605.7 461521.8,372209.8 460317.7,369352.3 461239,369714.2 464470.9,363191.2 470277.6,

363491 473169.9,365227.3 473672.8,370052.2 481319.2,370144.8 482748.7,362512.5 477911.7,358350.8 478665.3,355703.4 474137.7,

347972.3 478292.1,345446.8 475698.7,342749 476087.5,342784.7 474615.5,340414.8 475469.9,342882.8 469480.8,341304.5 465488.7,

344238.6 465331.3,340055 463217.2,340345.5 460141.4,335601.4 455045.4,336057.5 453597.1,332947.7 450366,329952.5 450443.2,

330737.1 442705.2,333041.8 441857.2,333572.8 437130.7,335319.6 433501.9,333963.4 433247,334425.2 431366.8,329729.3 431451.9,

329199.8 427517.3,328505.3 422791.4,330070.5 422095.3,336522 423531.2,337967.3 418422.4,332016.4 412241.1,332374.5 408594.8,

330736.4 405654.3,335390.6 402509.3))', 4277))

This is where things got a little tricky. The county boundaries used the OS coordinate system, whereas my postcodes were stored in latitude/longitude format. I was hopeful that SQL Server would do some magic for me and handle the different coordinate systems, but it would appear this isn’t the case.

So it looked like the only option was to convert my postcode points into the OS coordinate system. I’ve used phpCoord to do this conversion in the past, but this time I was looking for a .NET solution. So I took the Java implementation and converted it C#. That took a while (and I’ll upload the code at some point when I’ve OKed it with the original author) but after modifying my code to insert postcodes into the database I was able to run the following query and successfully pull out postcodes that were in the Lancashire area.

SELECT * FROM Postcodes WHERE (SELECT Boundary FROM CountyBoundaries).STContains(OsLocation)=1