Managing OS MasterMap

What is OS MasterMap
The latest generation of Ordnance Survey’s most detailed geographic data of Great Britain, is OS MasterMap. It provides consistent and up to date information down to address, street and building level and is available in four data layers: Topography, Address, Imagery and Integrated Transport Network (ITN).
OS MasterMap replaces Ordnance Surveys Land-Line® product, which was withdrawn from the market in September 2008.

Options for Managing OS MasterMap within AutoCAD
In the past Land-Line has been supplied in a CAD friendly format as tiled DXF or NTF files. Due to its simplicity, this data can be quickly and easily loaded into AutoCAD.
Due to its more complex data structure, rich intelligence and delivery mechanism, OS MasterMap is not suited to DXF or NTF formats. As such, the management of the data within an organisation requires careful thought, especially when considering how data can be accessed and utilised within an AutoCAD environment.

The problem with the DWG file
When MasterMap data is translated into a standard AutoCAD DWG using an external translator it will convert the MasterMap entities into CAD features. This will result in a loss of intelligence assigned to the data by the Ordnance Survey. This intelligence is a major advantage of the MasterMap data, as it allows you to produce powerful themes, link the data to external datasets and manage the life cycle of the data.
As MasterMap data is much larger than LandLine, when comparing the same area, it results in a much bigger DWG, leading to storage and speed problems.

The solution – AutoCAD Map
To enable AutoCAD users to manage MasterMap data regardless of the source or format it is recommended that they upgrade their AutoCAD licence to AutoCAD Map.
AutoCAD Map is based on open data standards giving organisations the flexibility to work with virtually any spatial data available. Whether data is stored in DWG, SHP, TAB, GML or other standard geospatial formats and databases, AutoCAD Map 3D can access, view and edit the data with speed and ease.

There are several options to manage the data in AutoCAD Map:

Option 1
AutoCAD Map allows the user to import the OS MasterMap GML data directly into the DWG without the need for an external loader. Within this import process, the user has full control over which layers and attributes to import, and can create a spatial query when loading the data to control the geographical extents of the data required.

Option 2
An alternative to importing the MasterMap data into the DWG is to ‘Connect’ to the data. AutoCAD Map uses an engine called Feature Data Objects (FDO), and is a new Autodesk tool for accessing features and geospatial data regardless of the underlying data store. When you access data through the FDO tool, you use an ‘FDO provider’ to connect directly to a data source. This source could be foreign spatial file formats such as MapInfo TAB files, ESRI SHP files or even OS MasterMap GML data.

Option 3
An increasingly popular way of storing MasterMap data and many other geospatial datasets is within a spatial database. Database storage makes spatial data easier to manage, and presents a seamless dataset to the user. AutoCAD Map will connect directly to a number of popular spatial databases, including Oracle, ArcSDE and MySQL.

Summary
The access of OS MasterMap data is a challenge to the CAD user, and even more since OS Landline was withdrawn from the market in late 2008. However through the correct use of AutoCAD Map and some careful thought and planning, MasterMap can be easy to manage and may well enable you to be more productive when using mapping data in the DWG.