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
This blog presents functions for Bing Maps Tile System for TSQL. This support includes converting Latitude/Longitude pairs to Bing Maps QuadKeys. The source for the functions is over at the Mircosoft site – an article by James Schwartz. They are donated to the public domain. Some tests include: I hope this is of use toRead More
GIS Desktop Software is the bedrock of how most people experience Geographic Information Systems. A limited selection of such products are: ArcGIS Manifold MapInfo qGIS FME (Feature Manipulation Engine) – not strictly a GIS but it can do most of the above. I have experience with all of the above. If anyone wants some help,Read More
The lack of an array datatype in TSQL can be overcome for geometry processing by use of a GeometryCollection as a data type and a set of methods to manipulate it.
This article demonstrates the power of database-based spatial processing. The business requirement is to determine, dynamically, the side of a land parcel that faces the street (could be single 2 point straight line to something more complex), and then determine the clockface direction from either ends of the frontage or the middle, to a object in the roads reserve (eg telecommunications pit).
This article shows how to create a GeoJSON Document from Selection of SDO_Geometry objects.
In some situations Quadrilateral polygon geometries in SQL Server Spatial can affect processing results. The best example of this is the identification of CircularStrings in polygon geometries. If quadrilateral objects are not identified, they end up being incorrectly converted. This function helps identify such polygon objects.
The STLineToCurve function analyses a LineString looking for CircularString elements among its vertices (often LineStrings are created from curve elements by “stroking” especially where the processing software does not support CircularStrings). Any constructed CircularStrings are combined with other LineStrings to create CompoundCurves or CurvePolygons.
This article shows how to use PostgreSQL’s XMLTABLE XML operator to process GML data and create PostGIS geometries.