Monday, 27 September 2010

Where are we?

Its a big blue ocean out there, so how do we know where we are?  How do we communicate with loved ones, or for that matter, with the coastguard if an emergency strikes?

In this age of technology, there is a plethora of gadgets and equipment to make the world smaller.  But as we are taught when we start out sailing, we shouldn't rely too heavily on electronics, in case of equipment or power failure.  We should at least have the same basic practical knowledge that our forefathers had, such as how to plot a course on a paper chart, how to figure out where we are with a magnetic compass, how to read the tide tables, and for the more advanced, navigation by the stars with a sextant.  Once we have mastered the basics, we are then able to better appreciate the gadgets that we use on a day to day basis, knowing that we have a manual backup when we need it.

For navigation, we use a GPS unit, which may or may not come with a built-in plotter (this allows us to plot a course, along with way-points and other fancy features).  These units communicate with a network of satellites in geo-stationary orbit around the earth, allowing for amazing accuracy (up to a few feet).

For our basic communication, we use a VHF radio, and these days the fixed-mount models come with something called "DSC", otherwise known as "digital selective calling".  What this means is that the radio is also able to transmit digital data such as a mayday message, along with our position (if the radio is connected up to a GPS unit), at the touch of a button.  This saves precious time if lives are at risk.

There are limits to the range of transmission of a signal from a standard VHF unit however, especially from the middle of a vast ocean (due to the power required for transmission, as well as the curvature of the earth preventing the signal from reaching a land-based receiver). So how do we send an emergency call if the VHF radio is out of range?  For regular communication, satellite phones come into their own - transmission of radio signals (these days the newer models include digital data transmission, such as email and internet) is directed up to a series of communication satellites, which relay the call on to land-based receivers.  For emergency communication, some very special gadgets have been on the market for a while now, called EPIRBs, or "emergency position indicating radio beacon", and these can be manually or automatically activated when the unit is submerged in water.  All ocean crossing vessels (including commercial vessels) should have these, and they have seved many lives.  They work by sending out a radio signal, along with the position (by means of a built-in gps unit) at regular intervals, for a period of days.

Other pieces of useful electronic equipment include NAVTEX (navigational telex) - a unit that receives weather and navigation information from stations around the world.  Radar is also highly desirable, especially in busy waters such as the English Channel, as it allows us to keep an "electronic eye" out on traffic.

We have most of this equipment on board, which increases our safety margin considerably, but all the technology in the world is useless if no-one knows how to use it.  Fortunately, most of the crew have some level of experience using this equipment, so we can share our knowledge with those that don't.

Until next time....

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