A common question that comes up in the various database forums (PostGIS, SQL Server, Oracle) is how to “grid” a linear or polygonal object. By “grid” one means work out the square pixels (rectangular polygons) that cover or define a vector geometry. Here is some SQL for doing this for PostGIS. Single Geometry The followingRead More
A common question that comes up in the various database forums (PostGIS, SQL Server, Oracle) is how to “grid” a linear or polygonal object. By “grid” one means work out the square pixels (rectangular polygons) that cover or define a vector geometry. Here is some SQL for doing this for SQL Server 2008 Denali. DenaliRead More
Here is a method for finding the centre of a circle and its radius from a polygon (x003) sdo_geometry. Some examples: The SDO_UTIL.CIRCLE_POLYGON function is trickier because it generates 8307 longitude/latitude data. So the above function, based as it is on projected data, can only give us a basic approximation. The returned radius is goingRead More
Other blog postings of mine have shown how the layer_gtype keyword in the PARAMETERS clause of an RTree spatial index can be used to constrain the sdo_geometry type being stored in a column. Remember, SDO_GEOMETRY is singly inherited: there is no POINT, CURVE, POLYGON etc sub-type. For this one must use the SQL/MM Type shippedRead More
Recently I was asked to review a database migration from one vendor’s database to another’s. The conversion involved geospatial data and database internal representations. I am not going to talk about who the client was, or what actually transpired, but the final report I submitted was edited by the client and the phrase “to industry-bestRead More
Over on Technet , the following question was asked: My question is, can you think of a way to recognize situations like this and merge and store them in a table before, we attempt mapping and spatial queries are performed? The following database level approach is one approach for ensuring any loader doesn’t load duplicateRead More
Over the past week I have been having a conversation with a customer around problems with using CASE WHEN THEN ELSE END constructs in SQL for turning WKT into SDO_GEOMETRY objects on INSERT. Now the customer was doing this sort of comparison for correctly processing WKT data values in an external file into SDO_GEOMETRY andRead More
I have been emailed by someone who is using ESRI’s sde.st_geometry in preference to Oracle’s SDO_GEOMETRY or ST_GEOMETRY for their spatial data storage in Oracle, wanting a version of my CENTROID pl/sql package that would allow for its use with ESRI’s spatial data type. This is what I was asked: First off love your blog,Read More
Changes to the CENTROID and TESSELATE packages, as well as a modification of the Windows install.cmd tool (improved error handling) and the method used to test for an XE database required a new upload of the two affected zip files holding the relevant packages and tools.
My original CENTROID package’s sdo_centroid() functions, when supplied with a multilinestring sdo_geometry, would “explode” the multilinestring into its component linestrings and calculate the centroid (mid-point) of the largest linestring. Some users have asked for the centroid package to return the centroid (midpoint) of the whole multilinestring. While the LINEAR package can do this, I haveRead More