Shorebased


How reliable is the information? As an official Electronic Navigational Chart (ENC) it has the same quality control as an official hydrographic office’s paper chart. The question is whether or not it’s the most up to date edition. We would need to verify what the latest edition is - this is a key point. Commercial electronic charts predominantly do not have approval from national authorities, nor can you be certain of the quality control measures in place. Plotters using non-official charts (collectively called electronic charts, or ECs) tend to open up with a ‘Not to be used for navigation’ warning.


How am I going to use this information? If we can verify that this edition 1.001 is the latest edition and are able to operate the software correctly, there is no reason why we cannot use the information on this chart for primary navigational decisions. To put this another way, assessing the underlying chart’s credentials is very much part of how much use to make of it for appraisal and planning. Next consider the functionality of the software for navigation. How much can we use the plotter’s functionality for execution and monitoring. Let’s look at the second screen shot and apply the same analysis:


All RYA Shorebased Instructors have access to the Training Plotter using the activation code contained in all instructor packs. Following activation your login details created during the activation can be used to install and use the plotter on up to five compatible devices.


www.rya.org.uk


What is it telling me? 1. First, what screen are we on. Here we are looking at the route monitor, which is a separate window in this app.


2. The orientation of the route monitor is set to route up, so the top of the chart represents the desired direction of travel.


3. The next waypoint is called Synka Fairway End, and is 1.33 miles away.


4. We are able to see the summary of our boat speed, direction and the distance and bearing to the next waypoint both graphically and in the text.


5. The total route is 38M and we are expected to arrive at 1451. 6. We are 33m to the right of track.


How reliable is the information? 7. We have already assessed the chart setup. The quality of the fix is shown as ‘recent’ with a Horizontal Dilution of Precision of 4.1. – a reasonably reliable fix. More information about the quality indicators on the plotter is available here: http://support.nunonavigator. com/help/Connect_a_GPS


The calculations are based on GPS input and do not take tidal streams or weather conditions into account. The ETA of 1451 cannot be relied upon as accurate - it is a projection based on current speeds over ground. The navigator would still need to be aware of the changing streams and sea states over the remaining three to four hours of the voyage to realistically get an ETA.


8. We have prepared clearing bearings from Leslie Head Light house, with the green sector showing the correct route to ensure clearing the deep water channel and the overfalls off Huckle Head. We can quickly verify the fix and our cross track using these bearings.


9. The chart is zoomed in to 1:40,000, it isn’t over-zoomed yet so we could benefit from zooming in further when checking where we are.


How am I going to use this information? With the information presented here we could use this system for primary decision making and navigation. We have the necessary


information to know when to be more cautious about the GPS fix, and the ability to verify this by a second means. A significant point that comes out of this is the terminology and what is behind that terminology. Not all plotters have the same abbreviations or imagery, but they tend to have similar information displayed. Students should know the meaning of the major abbreviations (DTR, VMG, HDOP, EC, ENC) and also be able to interpret this in the context of the real world. Although we have verified that this system can be used for primary decision making and navigation, it is not in any way a reflection of the full picture. There is still a need for the carefully appraised and planned information to be considered to modify the information being taken from the system. There is also a wide range of other inputs which may or may not be displayed within a chart plotter, such as barometric trend, cloud cover, sea state, visibility and traffic density, which must be taken into account when executing and monitoring your passage.


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