User manual

Table Of Contents
The B
T
values for the eight element data that illustrates the compass correction process
are:
N NE E SE S SW W NW
+7.2° +7.3° +7.4° +8.7° +11.2° +8.1° +5.3° +4.6°
Average angular bias: +7.5°
The bias angle varies with bearing over a range of 6.6°. The operator may choose to use
a constant correction, the average angular bias calculated by the programs, for example, or may
interpolate through each octant using the eight measurements of B
T
.
In addition, two programs that carry out the actual calculations are available. Using the
derived parameters and the known magnetic deviation for the site of the deployment, θ
H
, the
heading angle of the sting in mathematical compass coordinates, can be calculated.
()
DEVOST
S
O
S
O
H
MB
Y
YHY
X
XHX
++
=
θθ
1
tan
Mapping Velocity Measurements to the Cartesian Earth Frame
Mapping velocity measurements to the Cartesian earth frame requires the following:
Sting and acoustic path geometry of each ACM scan
Velocity transformation
Sting and Acoustic Path Geometry
The final four numbers in each ACM scan are the velocities along the acoustic axes of the
sting. For more information including a schematic that illustrates these definitions and
relationships, refer to Chapter 7, “Spin Test”.
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