Product supply

Available formats for Colour Raster Map products

The following table outlines the formats available for the three OS Colour Raster Map products. These include:

• TIFF LZW (Lempel Ziv Welch) is a lossless compression (see the data compression page).

• TIFF PackBits is a lossless compression scheme that is supported by virtually all applications that can import TIFF graphics.

• GeoTIFF LZW is a TIFF file which has geographic (or cartographic) data embedded as tags within it. The geographic data can then be used to position the image in the correct location and with precise geometry on the screen of a geographic information display.

• Windows® BMP is a historic file format for the Windows operating system. A compressed BMP format is also available using Run Length Encoding (RLE). RLE means that the file can be read from start to finish in one pass. A BMP file consists of either three or four parts. The first part is a header that includes the position of the image and the number of colours to be displayed. This is followed by an information section that contains the image width (part 2), height (part 3) and the type of compression (part 4).

1: 25 000	1: 50 000	1: 250 000
TIFF LZW	TIFF LZW	TIFF LZW
GeoTIFF LZW	GeoTIFF LZW
TIFF PackBits
	Windows® BMP

TIFF information

TIFF is a file-based format for storing and interchanging raster images, with the most recent version (6.0) published in 1992.

There are two types of architecture for a TIFF. Many mainframe computers use what is known as a big endian (Motorola®) architecture. Most modern computers, including personal computers (PCs), use the little-endian (Intel®) system. 1:50 000 Scale Colour Raster and 1:25 000 Scale Colour Raster TIFFs are supplied with Intel architecture.

Converting between these two systems is possible but, as a general rule, modern software should be expected to handle both of these outputs without operator intervention.

Both the 1:25 000 and 1:50 000 Scale Colour Raster maps conform to the TIFF 6.0 standard. Customers are recommended to contact their system suppliers to ensure that it can read the Intel/little-endian TIFF architecture.

Product supply mechanism

The GeoTIFF LZW compressed format is supplied as an online download which is available from the OS Data Hub. Other TIFF formats are also available from the OS Data Hub but as area of interest (AOI) downloads only (i.e. not as full supply).

The TIFF LZW compressed, TIFF LZW 8-bit uncompressed and Windows® BMP compressed formats are available for customers to request on DVD/HDD through OS Orders.

The product is updated quarterly. OS Partners can select a full supply option or a change-only update (COU) option. Public Sector Geospatial Agreement (PSGA) customers are only able to select the COU option. If you select the COU option, then you will only receive tiles that have changed since the previous supply.