Ordnance Survey National Grid – Bing Maps App

In a previous piece I provided a link to a map that uses this excellent application but because I am finding it extremely useful (especially in conjunction with Grid Reference data derived from other sources) I thought it warranted an entry to itself.

The best place to start is with an example so if you click here you should find yourself transported to Orinsay on the Isle of Lewis.

The image is a magnified version of the OS 1:25 000 map and the pale blue lines that run at right-angles are each 1 kilometre apart hence they divide the map into squares whose sides are 1Km long.

The 1Km square that is highlighted is called NB3612 and this reference is shown in the list to the left of the map.

The smaller square inside the 1Km one has sides that are 100m in length and it is called NB362120. The bottom-left-hand-corner of this square is two units (200m) to the East (Right) of the bottom-left-hand corner of the 1KM square which is why its name begins ‘362‘. This is called the ‘Easting‘.
The bottom-left-hand-corner of the square is zero units (0m) North (Up) of the bottom-left-hand-corner of the 1KM square which gives us the final part of the name, ‘120’. This is called the ‘Northing’.

The tiniest square has sides that are only 10m long and its name is NB36261205, locating its bottom-left-hand-corner 6 units (60m) to the East and 5 units (50m) to the North of the bottom-left-hand-corner of the 100m square.

Each time we move up in accuracy we add a new digit

I make no apology for repeating the term ‘bottom-left-hand-corner‘ because, once it is remembered as the origin for ALL measurements, regardless of which size square is being dealt with, then this system of ‘Eastings’ and ‘Northings’ becomes easy to use.

Note that we go ‘along the hall’ (Easting) before ‘climbing the stairs’ (Northing).
(That was how I was first taught the system when a ‘Wolf Cub’ (showing my age now!) and it is a mnemonic that I still find as useful today as it was 40+ years ago…)

This system allows us to identify any place on the map with a great deal of accuracy or, if given a Grid Reference, to see that place on our computer screen. The other great benefit is that, because the system is based upon the 1Km light-blue squares, we can gauge distances relatively easily regardless of how far we ‘zoom in’ to a place or what screen size & resolution we are using.

Finally, if you use the ‘-‘ & ‘+‘ buttons at the bottom of the screen to zoom out from the detailed view you will eventually see the yellow 10Km square, NB31, and finally the 100Km square NB.

This is a very valuable App and mention must be made of the person who developed it, Alastair Aitchison, and of another 60 Bing Map Apps that can be found here .

Note: You can double-click on a new location to have the map centred upon that spot with the Grid References displayed for the new place. If double-clicking doesn’t work, try zooming-out one level by clicking the ‘-‘ button then try the double-click again.

PS The OS have an interactive guide to the Grid Reference system, here , which is well-worth a visit especially if the system is totally new to you & my attempt at an explanation has left you confuddled!


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