BARTINGTON INSTRUMENTS
Page 6 of 32 OM2020/5
3. Introduction
The Mag-01H Declinometer/Inclinometer (D/I) System comprises a high sensitivity, battery
powered, magnetometer type Mag-01H together with a vector sensing fluxgate Mag A probe
which is mounted on a Wild T1 non-magnetic theodolite.
The system permits very precise angular measurements of the terrestrial magnetic field F. The
angular components measured are Declination D and Inclination I.
• Declination is the azimuth angle between the Geographical Meridian GM and the Magnetic
Meridian MM.
• Inclination is the vertical angle between F and the horizontal measured in the direction of the
Magnetic Meridian.
The value of F, together with the components X (MM horizontal), Y and Z (vertical) may also be
measured to an accuracy of 0.25%.
The system is suitable for permanent installation on a non-magnetic pillar in observatories,
using a pillar mounting plate. The provision of a non-magnetic tripod and the re-chargeable
batteries within the magnetometer also permit mobile observatory use, enabling highly detailed
mapping of D and I.
See
for further details of taking measurements.
The system is used in observatories to obtain reference data which may be used in the
construction of Reference Field Charts. See
for an example of an International
Geomagnetic Reference Field (IGRF) chart.
Note:
The Earth’s magnetic field is constantly changing. Current IGRF charts are available
from organisations such as the British Geological Survey (BGS) (
).
Other applications include checking of compasses and monitoring of the field for compass
correction purposes, or in-field referencing in directional drilling operations. Detailed knowledge
of local variation in D and I may be of assistance in interpreting total field magnetometer survey
data.
The ultimate resolution achieved with this system is limited by four factors:
1. Prevailing magnetic conditions.
Measurements during magnetic storms can be extremely
difficult to perform.
2. The degree of arc required.
The Wild T1 theodolite has a resolution of 6 seconds of arc, with
estimates possible to 2 seconds.
3. Plinth stability.
The tripod is less stable with time and temperature than a stone pillar.
Summary of Contents for Mag-01H
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