MANUAL – REFLEX EZ-TRAC™ | 17
Figure 5 Inclination 2005
5.3.1.3 Annual rate of change
The annual rate of change of the declination for 2005 to 2010
according to the British Geological Survey (Natural Environment
Research Council) is presented in the figure below.
The contour interval is 1’/year up to ±20’/year, thereafter 5’/year.
Figure 6 Annual rate of change
5.3.2 Background magnetic field
The local total magnetic field influences the measurements of
magnetic instruments. To be able to compensate for the background
magnetic field, a reference measurement made away from any
magnetic disturbances is needed.