Aug 052015

We are pleased to announce the release of DWG versions of both OS Terrain™ 5 (vector) and OS MasterMap® Topography Layer Building Height Attribute, which makes their use in CAD applications much easier and quicker.

Recently we have been working to produce DWG versions of the detailed vector dataset OS Terrain™ 5 and the popular Building Height Attribute component of OS MasterMap® Topography Layer. Both these datasets have proved popular with CAD users for detailed modelling applications but until now using them has proved time-consuming as many steps were required to convert them in to a format suitable for use in CAD applications.

OS Terrain 5 Vector

OS Terrain 5 Vector is dataset consisting of contour lines with five metre vertical spacing and spot heights (point features). The dataset also includes contours for mean high and low water around coastal areas, along with labels for both spot heights and contours.  OS Terrain 5 is the most detailed height dataset available from Ordnance Survey. A Digital Terrain Model (DTM) version is also available in ASCII grid format and can be downloaded through Digimap.

Building Height Attribute (BHA)

As with the other BHA datasets provided through Digimap the DWG version is supplied as a dataset of building polygons together with the building height attributes supplied by OS in the latest alpha release of their Building Height Attribute dataset (December 2014 at the time of writing). The DWG dataset is a 3D dataset which uses two of the height attributes supplied by OS to create the 3D features.  The base height of buildings is set using the value of the AbsHMin attribute and the roof height is defined by the AbsH2 attribute:

BHA Attributes

All height attributes supplied by OS, as indicated in the image above, are included as XDATA which can be readily viewed in CAD applications.

Note: the DWG BHA dataset is not supplied with a terrain surface so the building features will appear to float above the surface if it is displayed without a suitable terrain surface. We recommend using either OS Terrain 5 or OS Terrain 50, both of which can be downloaded from Digimap.

The image below shows OS Terrain 5 vector overlaid with BHA in AutoCAD 2015 for the area around Edinburgh Castle. Both datasets were supplied by Digimap in DWG format and required no manipulation or processing in order to display them.

OS Terrain 5 with Building Height Attribute

OS Terrain 5 vector and OS MasterMap BHA datasets are supplied on a 5x5km grid, so you may receive multiple multiple files if your area covers more than one 5km grid square.

We hope this makes it much easier to use the data and we welcome any feedback you may have.

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