OS MasterMap Imagery Layer

OS MasterMap Imagery Layer can be used in applications often reducing the need for costly site visits:

• Property insurance

• Risk analysis

• Asset management

• Site evaluation

• Land-use cover analysis

• Agricultural land use and crops inventory

• Property management and planning applications

• Route planning and accessibility assessments

• Location-based services

• Vegetation studies and environmental analysis

• Access: Download and hard disk drive (HDD)

• Data theme: Contextual

• Data structure: Raster

• Coverage: Great Britain

• Scale: 1:1 250 to 1:10 000

• Format: JPEG, TIFF, ECW

• Ordering area: All of Great Britain or customisable area (1km² tiles)

• Publication months: February, May, August, November

• OS Data Hub plan: Premium Plan, Energy & Infrastructure Plan

Ensuring the quality of OS imagery

Ordnance Survey has invested considerable resources and worked closely with its imagery suppliers to provide orthorectified imagery that achieves the consistently high quality expected by our customers.

Unlike other data sources, such as topographic data, imagery can be very subjective. It is difficult to quantify specific tolerances for atmospheric conditions, such as haze. We ensure our suppliers adhere to a detailed set of quality levels for the key aspects of imagery with an emphasis on data quality over image appearance alone. For instance, priority is given to ensuring details such as road markings can be seen within shadows and to positional accuracy.

These acceptable quality levels are summarised in the user guide and include:

• The photography and how it is captured

• The controls and height models used for orthorectification

• Geometric fidelity (shape), absolute accuracy (position), radiometric accuracy (colour) and image appearance (contrast, haze, cloud cover and distortions)

Active capture programme

More than 99.99% of our imagery is less than 5 years old; 76.36% is less than 3 years old.

OS MasterMap Layers are designed to be used together

As the OS MasterMap Imagery Layer is a raster product, unlike the other (vector) layers in the OS MasterMap product range, TOIDs are not part of the data specification. However, OS MasterMap layers are designed to be used together in order to create a synchronised tool for analysis of many different types of data in a GIS. Thus other layers can be drawn over imagery to provide information, such as TOIDs.

All imagery since 2015 is 'True' Orthorectified (without building lean)

However, within these images there may be small patches of 'traditional' ortho (with building lean) which have been introduced to resolve geometric or image appearance / artefact issues. Whether 'True' or 'traditional' Ortho, buildings should always be geometrically correct, located in their correct geographical position and suitable for analytical interpretation.

Great care is taken to ensure that the images in the Layer meet our detailed Image Appearance criteria

However, on occasion and under certain circumstances, these rules are relaxed. For example, if opportunities to capture new imagery have been limited by poor weather and existing imagery in the Imagery Layer is deemed out-of-date, then imagery will be accepted provided detail is visible on the ground. In these circumstances, image currency takes precedence over image appearance.