The SD7217 Square Kilometre

SD7217 National Grid Square

Based in the North West English Region.

The SD7217 square kilometre intersects with the settlement of Entwistle.

SD7217 is within the post town of Bolton, Lancashire.

The square is within Blackburn with Darwen council.

The Point of Origin (0,0) is 558.81 Kilometres away. This is where the National Grid starts around 80 kilometres west of the Isles of Scilly.

Ordnance Survey Maps for SD7217

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Map Series	link	Ordnance Survey
Explorer 1:25,000 287 West Pennine Moors - Blackburn, Darwen and Accrington	Shop for this map on amazon.co.uk
Landranger 1:50,000 109 Manchester Bolton & Warrington	Shop for this map on amazon.co.uk

This extract is taken from the Ordnance Survey six-inch to the mile series surveyed from 1888-1913. The scale is 1:10,560.

The Square overlayed over the map represents the extent of SD7217 and the vertical and horizontal line divides the square into four quadrants

Dividing the SD7217 Square to get a six figure Grid Reference

A helpful reminder for calculating grid references is across the landing and up the stairs.

For example if your house was located in a square that in the fourth square across and sixth square up and you wanted to work out its six figure grid refence.

First, You would divide the four figure grid reference into three parts. SD , 72 and 17

Count across starting with zero. This would give you three. Make a note that X for Across (A Cross) = 3.

Count up starting with zero. This would give you five. Make a note that Y = 5.

So to put it together SD + 72 + 3 + 17 + 5 would give you the six figure grid reference of SD723175

SD	72		17
SD	72	3	17	5

A six figure grid reference would be accurate to 10 metres. To achieve a greater level of accuracy this 10 metre square would be divided into a grid 10 by 10 and the process repeated.

This would produce an 8 figure grid reference that would be accurate to a square metre!

Corner	Latitude	Longitude	Easting	Northing
South West Corner	53.648763	-2.425152	372000	417000
South East Corner	53.648763	-2.409934	373000	417000
North West Corner	53.657804	-2.425152	372000	418000
North East Corner	53.657804	-2.409934	373000	418000