User Manual: Generic Section
Section: Introduction 0-4
Revision: 00
Page
12 of 21
Sonardyne Systems
Term
Definition
Sound Speed Profile
At different depths the temperature, salinity and pressure vary,
so the local sound speed varies.
Depth cannot be measured directly. So pressure
measurements are taken, and the depth calculated, using
knowledge of density and local gravity. Derivation of density
requires knowledge of temperature and salinity. Salinity cannot
be measured directly but conductivity can be measured.
A method of measuring the sound speed profile is from a
profile of pressure, temperature and conductivity and a formula
to compute depth and sound speed.
Submersible
A vehicle that operates below the seas surface.
It can carry men in a one atmosphere environment with one
man piloting the craft.
It has a supply of air for the crew and a supply power for
propulsion etc. It can operate autonomously form a vessel for
a limited time.
True North
The direction of the shortest line that can be drawn, across the
surface of the earth, from the observer and the north pole.
(The north pole is where the north end of the spin axis of the
earth meets the surface.)
Universal Transverse Mercator (UTM)
A Projection system that is used to transform Geodetic co-
ordinates into an orthogonal two dimensional system suitable
for representation on a plane such as a chart. The co-ordinates
are called easting and northing which are equivalent to x and y
respectively. The UTM system is a world wide system.
Each projection covers 6 degrees of longitude with the central
meridian at 3, 9 degrees etc east of Greenwich and from 84
degrees north to 80 degrees south. The scale factor on a
central meridian is 0.9996 (with some exceptions).
The projection is orthomorphic this means at a point the scale
in all directions is the same there is no local distortion. NOTE:
Scale factors change with distance from the central meridian.
For points away from the central meridian grid north and true
north diverge. The difference is called the CONVERGENCE
which is positive when grid north is east of true north. The point
where the central meridian meets the spheroid equator is given
a false easting of 500,000 m. Many countries’ mapping
systems are based on the same system but use a particular
reference spheroid.
Summary of Contents for 8142-000-01
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