Potential Side-Effects of Improved Spatial Precision in SQL Server 2012 and the SQL Azure September 2011 Service Release

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In Microsoft SQL Server 2012 (previously known as SQL Server Code-Name “Denali”), all constructions and relations are now done with 48 bits of precision, compared to 27 bits used in SQL Server 2008 and SQL Server 2008 R2. This can result in differences that range from how individual coordinates (vertices) in spatial objects appear (rounding) to how computational results are produced in different versions of the database server for certain spatial operations.

Recently, SQL Azure has been upgraded in all data centers to incorporate the new SQL Server 2012 spatial library. This upgrade, known as the September 2011 Service Release, thus enables spatial operations in SQL Azure to be the computationally identical with SQL Server 2012.

Because of this new feature, results from spatial operations in SQL Azure September Refresh and SQL Server 2012 can differ from results produced in their respective prior versions. This technical note reviews the effects of the precision change and assists in identifying potential migration issues..