The National Grid provides a unique reference system that can be applied to all Ordnance Survey (OS) maps of Great Britain, at all scales.

On the map of Great Britain on the Professional Maps home page you will see it is covered by 100 kilometre grid squares (or 'tiles'), each being identified by two letters; e.g. Lands End is in grid square SW.

On OS maps these squares are further divided into smaller squares by grid lines representing 10 kilometre spacing, each numbered from 0 to 9, from the south west corner, in an easterly (left to right) and northerly (upwards) direction.

Using this system, you can identify a 10 kilometre grid square. After the letters you quote the Eastings ( the numbers across the foot of the sheet), then the northings (the numbers up the side). If you have difficulty remembering which numbers come first say ' Along the hall (bottom numbers) and up the stairs (side numbers)'.

On OS 'small scale' Landranger maps (the ones with the pink covers) you can find the two grid letters on the legend, or on the corner of the map, and the grid has been further divided into 1 kilometre intervals. You can estimate distances between the grid lines to give a more accurate reference.

The 6 Figure Grid Reference is very useful to locate your particular place of interest on a map and can be used on this Blackwell's Mapping service to go directly to the place. By estimating the eastings and northings to one tenth of the grid interval you can specify your full 6 Figure Grid Reference.

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When you view the national map of Great Britain you may enter a 6 Figure Grid Reference or a two letter 100 kilometre square reference or the Post Code of a property.

When you see a large scale map come up on the screen that includes the area or property in which you are interested, select an area by drawing one side (the base line) by dragging in any direction, and then dragging away from that base line to form a box that includes your location. Click on order, choose which product you would like, enter your contact details, choose which of Blackwell's seven Map centres you would like to process the order, and click on Finish Order. On receipt of the order Blackwell's staff will contact you with a firm quotation.

The Professional maps home page explains the types of large scale map you may wish to receive. You have both a choice of products and format too; do you want a paper map or you can have an electronic version, sent by email, or on a 3 1/2 inch floppy disk or on CD-ROM. You may also have the map printed on film for presentation purposes.

Examine too our payment options. We offer business, educational and private map buyers a wide variety of payment methods.