Fixing Geography Ring Orientation
This article demonstrates the effect wrong ring orientation has on the processing of a geography object and shows how to fix such orientation.
Algorithms
Some article are about algorithms, some about implementations, some about low level functions.
Delaunay Triangulation Function for TSQL and SQL Server Spatial
This article shows how to create a delaunay triangulation (mesh) from various inputs in SQL Server Spatial, and compute the 3D (slope) area.
Removing Spikes in SQL Server Spatial Linestrings
This article presents a method for identifying and removing spikes in SQL Server Spatial linestrings and polygon rings. Spikes are common when processing GPS observations.
How to calculate cumulative length of a linestring, or the truck tonnage that accumulates across a set of roads
This articles describes how to compute the cumulative length of a single linestring, or the total tonnage that crosses a set road segments.
Snapping a Point to an Oracle Spatial SDO_GEOMETRY LineString
This article shows how to snap a point to an Oracle Spatial linear geometry using the SDO_CLOSEST_POINTS procedure and function
Oracle Spatial Vector Acceleration: Flick the Switch
Introduction A lot has been written, positive and negative, about the speed of Oracle Spatial over the years, a lot of ill informed (I mean if you don’t use it, how can you criticize it?). But since Oracle Database 12c (12.1) there is no longer any doubt as to the speed of the product. Why?Read More
CheckRadii: Identifying Tight Radius Curves sections within LineString geometry data
Sometimes it is a data quality requirement for linear data (roads, pipelines, transmission lines) that curves within the lines must have a radius greater than a particular amount. Recently a customer asked me to write some TSQL functions to help them run data quality checks over linear data loaded into a SQL Server 2008 geometryRead More
Overlaying Polygons in SQL Server Spatial
Introduction The OGC operators for geometry processing only support two polygon inputs. Additionally the Microsoft aggregate operators only include geometry union processing geometry::UnionAggregate and not overlay processing etc. UnionAggregate returns for all input polygons as the single Union (see above) does. Concept: Resolving all overlapping areas, without dissolving boundaries, is called “planar enforcing”. Planar enforcementRead More
Space Filling Curve Functions For TSQL
Introduction Warning: This article is long mainly because it includes the source code of the Hilbert, Morton and Peano key/curves. I would assert that space filling curves have always been overlooked in their use within GIS. Their existence was/is rarely taught at Universities, though at least in my day. Perhaps today it is different (butRead More