Ordnance Survey maps come in two main scales, 1:50,000 called Landranger and 1:25,000 called Explorer. They use a grid system of squares measuring 1 square kilometer identified by 4 or 6 figure grid references. Each map sheet has a two-letter code to identify its location. Symbols in the map key represent features to provide information efficiently without cluttering the map with text labels.

1. Features of Ordnance Survey Maps
There are 2 main scales of OS maps sold in shops, although others are
produced.
The 1: 50 000 scale is called the Landranger (pink)
The 1: 25 000 scale is called the Explorer (orange)
All maps are drawn to scale which means they are smaller than the ‘real
world’.
They have a grid of blue lines. Each squareis always 1 squarekilometre – a
squarewhich has sides 1kmlong.
The lines havenumbers on them which allows for the calculation of 4 figure
grid references to identify each square, or 6 figure grid references to identify
features within a square.
Each map sheet also has a two-letter code to identify it and help make sure
that the grid reference is accurate. The Ely map has the code TL.
OS maps always have north at the top of the map, and the rest of the compass
directions can be worked outfrom there.
Maps have a key or legend which identifies the symbols.
Symbols areused to show information in a way that doesn’tget in the way of
other information, reducing the need for text labels. They can also be
understood withoutthe need to know the language. They areshapes, colours,
lines or pictures, plus abbreviations of longer words.
Blue symbols areusually linked with tourism.
The more the map zooms in the more detail is revealed, but the smaller the
area that is shown on the map.