Geoscience Reference
In-Depth Information
1. Identify features
Identify two features on the map and on the
ground on which to take bearings. In this
case the purpose was to identify the
location along the exposure known as Coe
Crags (shown on the map by the end of
the pencil). Various landmarks can be
picked out on the hills to the north.
2
2. Measure azimuth
Hold the compass horizontal at waist height
with the back of mirror towards you and the
mirror at about 120
°
to the compass window.
Line up the feature so that you can see
the feature through the long sight in the
mirror, ensuring that the compass is level
using the round spirit level.
Read off the azimuth.
3. Orientate the map
Put the compass-clinometer on to the map
with the long edge of the compass-
clinometer parallel to a N-S grid line.
Check that you have the compass the
correct way round and not 180
°
out,
i.e. that the north needle is pointing roughly
north on the map. Rotate the map and
compass together until the north needle is
at its zero mark.
Figure 2.11
Triangulation using a Brunton-type compass. The terms for the different parts of the compass-
clinometer are given in Figure 2.3a-c. (Map: Ordnance Survey, Landranger Series, Sheet 81. Ordnance Survey
on behalf of HMSO © Crown Copyright 2010. All rights reserved. Ordnance Survey Licence number
100018362. (extract is from within 10 km grid square NU(46)00.)
