The detail and accuracy of urban maps are set to be improved by an Ordnance Survey programme supported by Land Registry.

Ordnance Survey (OS) has understandably given priority to recording significant topographic changes throughout Great Britain over the last 30 to 40 years.

This has meant minor changes in urban areas have not been systematically picked up.

Now, however, it is embarking on an Urban Content Improvement (UCI) programme to improve the data shown on its MasterMap Topography Layer in urban areas. This will mainly affect 1:1250 mapping.

High-resolution aerial imagery

OS aims to capture around 14,000 km2 of urban geography over an estimated three years, using high-resolution imagery from aerial photography.

The existing urban map detail will be compared side by side with the aerial imagery. Any new features will be plotted and existing features which fail the set quality standards will be moved.

This will be supplemented by the work of surveyors in the field where detail is obscured or unclear.

OS is conducting a trial focused on the Bristol and Bath area to establish the best methods of delivering UCI. Once completed, it will look to roll out a nationwide approach to other urban areas.

More accurate and detailed urban maps

UCI follows the Positional Accuracy Improvement (PAI) programme which principally affected 1:2500 mapping.

Unlike PAI, where significant differences in the position of map detail were seen, UCI will mainly bring small changes and differences to urban maps. In most cases you will see detail added rather than moved. Land Registry practice has not been changed to reflect UCI.

The main changes to urban maps will be:

  • more building extensions and private garages shown
  • minor paths, such as those in parks and cemeteries, kept more up to date
  • better recording of the continuation of one feature under another, such as a river under a bridge
  • reclassification of line work, such as where a wall has been removed to allow for front-of-property parking
  • inclusion of changes relating to important detail where change is often difficult to detect, such as kerb alterations.

By improving accuracy to better reflect the real world, the changes will go further than just adding detail to urban maps.

aerial photography with OS layer 51113

Aerial photography from 2011 overlaid with the MasterMap Topography Layer

Collaborative approach

OS has adopted a collaborative approach, outlining its intentions at workshops held around the country in which Land Registry took part.

The guiding principles are to:

  • deliver consistency of content, ensuring that real-world objects are captured, modelled and maintained in a consistent fashion and existing inaccuracies are eliminated
  • ensure that all features are maintained over their lifecycle
  • improve the description of a feature, particularly in terms of its form and function, in addition to what it looks like from above.

Full details of the current areas affected by the UCI programme can be found on the OS website.

Gary Osborne
By Gary Osborne,
Surveying Services Manager at HM Land Registry.