Styling method overview

To overcome the challenges posed by multiple styling methods and to ensure that users get the most out of the detailed content available, Ordnance Survey developed a post-processing method to create a new discrete style attribute that can be used to style OS MasterMap Topography Layer.

We created a key attribute, “style_code”, which is populated with integers that correspond to a style for a given feature. This code is based on logic similar to the process described in our Standard Styling Specification, but with far fewer unique feature styles. We chose to use integers, rather than text, to improve system performance during processing. The use of integers, together with a text description, makes the new styling easy to understand and apply.

Provided resources

Styling information, SQL scripts, stylesheets and related resources are available from the Ordnance Survey OSMM-Topography-Layer-stylesheets GitHub repository.

To support the wide variety of OS MasterMap users, the provided resources include:

• Stylesheets: In SLD (Geoserver), LYR (ESRI Layer), LYRX (ArcGIS Pro), QML (QGIS) formats in a backdrop style, and Mapbox GL styles.

• SQL database scripts: For Oracle, PostgreSQL/PostGIS and SQL Server to post process your database.

• Symbology fonts: OSMasterMap TrueType font and SVG images.

• FME: Transformer(s) for FME Workbench.

• QGIS-Field Calculator: Text files and instructions on how to use the QGIS field calculator to add styling attribution.

Methodology

To create the post-processing styling method, we followed these steps:

1. Queried the OS MasterMap Topography Layer database to create a list of discrete features grouped by combinations of descriptiveGroup, descriptiveTerm, make and physicalPresence. The results were ordered by total count.

2. Added a styling description for each combination.

This was done by the Cartographic Design team who considered whether each discrete feature should have its own style rule or whether it could be styled like a similar feature.

1. Added a numerical styling code.

This was based on previous feedback from users who had used the “os_cat” styling method. Using numbers has

important performance benefits; a stylesheet looking to match data with “Building Outline Line” is significantly slower than one matching with an integer value of “2”, for example.

Total discrete feature count for Topographic Lines

Total count	feature Code	descriptive Group	descriptive Term	make	physical Presence	Styling description	Code
148 127 807	10046	General Feature			Obstructing	Default Line	1
64 612 785	10019	Building	Outline	Man-made	Obstructing	Building Outline Line	2
29 515 251	10046	General Feature			Edge / Limit	Edge Line	3

1. Wrote SQL database scripts that post processes the database tables to add the new styling attributes, and stylesheets that look for the new style code attribute.

The attribute tables section contains tables that list the attributes used to create the new style rules for each OS MasterMap Topography Layer type.