Introduction The ordinates stored in an geometry objects, across all spatial data types do not have any rounding applied to their values. This is one aspect of data management that is seldom considered by most practitioners. Other articles in this website deal with how to round their values. This article is about a related topic”Read More
This article demonstrates how an invalid polygon (and linestring) are handled by the different database spatial APIs with correction in TSQL.
This articles logically steps through all the functions in a complete package of Linear Referencing functions that I have written for TSQL. The article both demonstrates the power of SQL Server Spatial but what can be done with TSQL.
1. Solutions Architecture. I discovered over the years that I am a pretty good systems and solutions architect. How does this apply to you? Well, let’s say you have a business problem you want to be solved. You have a bunch of technology options that provide a framework (or constraint) for delivery, and want toRead More
Introduction Data Structure + Base Function Accessors and Setters Four functions are declared for processing geometry or geography data within the array. These are “wrappers” over _STArray. Examples Declare @array xml select ‘Empty Array’ as test, [dbo].[STNumArray](@array) as arraySize; test arraySize Empty Array 0 Set @array = [dbo].[_STArray](@array,1,’insert’,geometry::Point(1,2,0).STAsBinary(),0); select ‘Insert into Empty ‘ as test,Read More
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
The background to this blog comes from two separate sources: the first is my testing of SQL Server 2008 “Katmai”, and secondly, a blog article that Charlie Savage wrote a while back on The Sad State of GIS Web Standards. Web Mapping Standards As an ex-GIS Manager who monitored GIS standards for possible deployment withinRead More
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
Comment: This article was written about 10 years ago. Most of what is written is still relevant though the comments about disk usage and access do not apply if SSD is being used. Introduction There are lots of things one can do to improve performance in mapping environments because of a lot of the visualisationRead More
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