2011

Table Of Contents

Using Expressions to Find Invalid Geometry

SQL Server provides a function called STIsValid() that returns 1 for valid

geometries and 0 for invalid geometries. FDO exposes access to that function

using a function called IsValid(geometry) at the FDO level. You can use this

function in AutoCAD Map 3D and MapGuide when you create an expression

to filter or select data. If you select data using no filter or using just the

EnvelopeIntersects filter, you can create a calculated property in the Data

Table using the IsValid function to see which geometries are valid or invalid.

Correcting Invalid Geometry

SQL Server Spatial also provides a function you can use to correct invalid

geometries on the server. You cannot use this function from within AutoCAD

Map 3D and MapGuide, but you can use it directly against SQL Server, for

instance, using Management Studio. Here is an example of this method:

update dbo.road set geom = geom.MakeValid() where geom.STIsValid()

= 0;

This operation makes the geometry valid by modifying its invalid parts. You

may prefer to edit the geometry yourself, rather than use a default correction

with uncertain results.

For more information on the STIsValid() and MakeValid() functions, as well

as other aspects of SQL Server Spatial, consult the SQL Server Spatial online

documentation.