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Working with Maps

How to read and give a map reference

The British National Grid enables a recognised reference to be given to any location in England, Scotland and Wales. Map references using the National Grid can consist of 2 letters followed by 2, 4, 6, 8 or more numbers, or can be given using numbers only. The more numbers used, the more precise the map reference is.

The letters refer to the 100km grid square the reference is within.

The first half of the numbers following the letter refer to the east/west position (called an easting), while the second set refers to the north/south position (called a northing).

The 100km squares for Great Britain

100km Grid Squares for Britain

As the following grid squares: HP, HT, HU, HW, HX, HY and HZ are more than one thousand kilometres north of the grid's origin the numeric value of the square's second letter is represented by two digits. When creating numeric grid references for these squares the northing increases by one digit so HZ1234 becomes 412, 1034 and HP567123 becomes 456700, 1212300.

Giving a map reference

An example map reference ST391578 consists of 2 letters (ST) that identify the 100km grid square, 391 is the easting, and 578 is the northing. This map reference is precise to the nearest 100 metres.

The 100km grid square ST is shown below.

100km grid square ST

Each 100km square is then broken into 100 10km squares and referenced by the easting first, then the northing. The two squares on the diagram shown below would be referenced as ST64 and ST87 respectively.

Referencing 10km grid squares

So the 10km square for our grid reference ST391578 is referenced as ST35:

Square ST35

And the 1km square is referenced as ST3957:

Referencing a 1km square

Our grid reference ST391578 can be used to locate Yarberry Standing Stones.

Alternatively you can used the full numeric grid reference by substituting 3 and 1 for ST as shown in the following table.

Precision of map references
Number and Letters Numbers only Precision
ST 31 100km
ST35 33 15 10km
ST3957 339 157 1km
ST391578 3391 1578 100 metres
ST39155785 33915 15785 10 metres
ST3915157851 339151 157851 1 metre
Where map references are displayed in MAGIC

Map references are normally displayed in the status bar at the bottom of the map window when the cursor is hovering over a point on the map:

grid reference help

They are also displayed after clicking the 'Where am I?' tool Where Am I Toolthen clicking on the map on the point you want the grid reference for:

Where am I tool Pop up

When you use map references

You can use map references in the search bar on the map page. You will firstly need to select the correct search criteria (Coordinates/Positions) by clicking on the map search bar arrow:

Search Options

Search Type
Search Grid Reference or Coordinates
How to form IACS compliant field numbers

While MAGIC does not store IACS data, IACS compliant field numbers can now be viewed using the Where am I? Where Am I Tool tool in the interactive map – see the help library for details of how this tool works. Go to the IACS Compliant Field Numbers page for further information on how IACS field numbers are formed.