typo SELECT ST_Difference(ST_SetSRID(ST_Extent(the_world), ST_SRID(the_world)), the_world)
________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Obe, Regina Sent: Thursday, August 07, 2008 9:29 AM To: PostGIS Users Discussion Subject: RE: [postgis-users] creating a mask Erik, I think the ST_Difference function may work for you. Basically get the extent of your world make a polygon out of it and then subtract the world So something like the below SELECT ST_Difference(ST_SetSRID(ST_Extent(the_world), ST_SRID(the_world), the_world) Hope that helps, Regina ________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of erik Sent: Thursday, August 07, 2008 9:11 AM To: PostGIS Users Discussion Subject: [postgis-users] creating a mask Hello, I don't know if the terminology I use is correct but I would like to create a mask of layer I have. For example, from the shape of the world I would like to keep only the oceans, the negative of the initial shape. I haven't found any info or documentation about this. Can this be done in PostGIS? Many thanks! Erik ________________________________ The substance of this message, including any attachments, may be confidential, legally privileged and/or exempt from disclosure pursuant to Massachusetts law. It is intended solely for the addressee. If you received this in error, please contact the sender and delete the material from any computer. ________________________________ Help make the earth a greener place. If at all possible resist printing this email and join us in saving paper. ----------------------------------------- The substance of this message, including any attachments, may be confidential, legally privileged and/or exempt from disclosure pursuant to Massachusetts law. It is intended solely for the addressee. If you received this in error, please contact the sender and delete the material from any computer.
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