Navigational Exercise

The Beginners Guide to Navigation

Most rallies these days are planned on the 1:50000 metric Ordnance Survey maps. The scale of these is approximately 1.25″ to 1 mile. The basic reference for any point on a map is a six figure reference, eg 744591. The way to remember which grid reference to read first is ‘crawl before you walk’, i.e. the first three reference figures should be read from grid markings along the bottom of the map and the last three from markings up the side. The six figure reference gives an accuracy of position within 100 metres. Occasionally a reference will be given with eight figures, or else a half will be used – this is to accuratetly define a junction say, where confusion may exist with only six figures given. An example can be seen on map 172 Bristol and Bath (version A3). Map Ref. 707563 1/2 – the T junction of the two yellow roads near Shoscombe. Map ref. 707563 would be the junction of the white and the yellow.

The next type of instruction gives directions associated with a reference, e.g. WSW734589NW. This shows you approaching the crossroads from West of South West (Upper Hayes) and departing to the North West (down the yellow towards Combe Hay). A series of references can be given, out of order, in the following manner: From control 734589NW pass through the following references, which are not in order, using coloured and white roads, and not going back on your route: 721 1/2 603 : N730604 : E715617 and finish at control N716595. Your route should up the yellow, into Combe Hay village, left up the white, left down the white past Week Farm, right up the yellow to the school, through Middle Wood, right up the white, down to reference 721 1/2 603 and down the white to join the A367 lOOm North of the control point. It may be possible to do it a different way, but the way shown is the shortest.

Places may be specified as being a distance from a map reference such as:- go to crossroads 6Km from 681630 1/2 and 2Km from 735594 1/2. You should be at map ref 718583, the entrance to the white at White Ox Mead. Although two positions are possible from these instructions, if you plot the other intersection of the two distances you will end up near Sulis Manor and not at a crossroads. Of course you will need a pair of compasses to plot these references but the scale is easily taken off the grid lines which are 1Km apart.

Pictorial route directions may also be used, the best known method probably being the “Tulip” diagram. This first appeared on the Dutch Tulip Rally many years ago. The principle of this method is to show a diagram of all road junctions on the route. The diagrams show the junction as it is displayed on the map, rather than how the driver sees it. The dot shows the direction you arrive from and the arrow the direction to go

Necessary equipment and more complex navigation

Essential Equipment

When taking part in an event you will need to equip yourself with the following items:

  • MAPS
    Road events invariably use Ordnance Survey 1:50000 metric maps, which are regularly revised and updated (the version number being given at the bottom of the legend e.g. 172 A3). It is worth having the latest edition, or at least marking new roads, etc. on to an older map, or the route instructions are unlikely to fit. 
  • ROMER
    An essential device for quick accurate plotting of map references. The Club has a stock of these available. It’s very easy to lose a romer, so attach a length of string to loop around your neck or wrist. 
  • MAP LIGHTS
    To supplement the usual dim interior car lighting. Keen types also invest in map magnifiers, which are magnifying glasses with a built in light source. 
  • MAP BOARD
    A sheet of stiff card to support the map while plotting. 
  • PENCILS
    Pencils and a rubber are also essentials, while many navigational events may also call for a protractor, drawing compasses or a ruler, and a calculator may also come in handy at times.
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