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What format is OS MasterMap Imagery Layer delivered in?

The OS MasterMap® Imagery Layer is supplied in 1km x 1km tiles in your choice of the following formats:

  • Tagged Image File Format (TIFF);
  • Joint Photographic Experts Group (JPEG);
  • Enhance Compression Wavelet (ECW); and
  • Multi-resolution Seamless Image Database (MrSID).

All files are accompanied by the relevant georeferencing files to enable integration in a GIS. The main features are summarised below.

TIFF (46.9mb) is one of the most commonly used lossless image formats. TIFF is primarily designed for raster data interchange, and is supported by numerous image-processing applications.

The other 3 formats are compressed to reduce their file size and facilitate data management.  These formats are recommended for very large or national coverage orders. As file compression can vary, the following file sizes are average.

A JPEG (4.2mb) image uses a lossy compression format. It is designed for compressing either full-colour or greyscale images of natural, real-world scenes and so works well on photographs, becoming the standard format for web site applications.

The ECW (4.2mb) raster image uses wavelet compression software which has been designed to compress, display, Internet serve and distribute imagery. The key characteristic of such compressions is that they are able to preserve a very good quality of the image with high compression ratios.

MrSID (4.5mb) is a wavelet-based file format for large raster images that enables instantaneous viewing and manipulation of images locally and over networks while maintaining maximum image quality.

Please note, only one format can be supplied per order. For both ECW and MrSID files, a plug-in is normally required. Customers are advised to consult the suppliers of their image viewing software to discuss format requirements prior to placing an order for imagery.

Further technical details are available in our user guide.

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For general enquiries, complaints, feedback or suggestions, email: customerservices@ordnancesurvey.co.uk or call us on 08456 05 05 05