All over the world, nautical charts use the same conventions specified by the International Hydrographic Organisation. The major symbols and abbreviations are identical. Some colours and some written abbreviations vary with the country and language.
For British waters most seafarers use official Admiralty charts prepared by the UK Hydrographers' Office. For a list of UK charts and many worldwide charts go to www.ukho.gov.uk and download the digital catalogue. For popular parts of the British coast go to the Admiralty Leisure website. A thick A4 booklet entitled "Symbols & Abbreviations Used On Admiralty Charts" is sold separately as Chart 5011. A yacht chandler will stock the charts for the local area and will be able to order charts for other regions. You can obtain others by mail order. See Kayarchy Shopping.
If you are in an area which gets a lot of leisure traffic you could use a similar yachting or kayaking chart from an independent publisher. These usually have more information about the layout of small creeks and harbours, whether the foreshore is sand or mud, and the location of waterside shops, and they often include a simple tidal atlas of the area.
Ideally a sea kayaker will have both an Ordnance Survey map and a maritime chart covering any unfamiliar area (s)he intends to explore. A chart shows the depth of the sea, gives some information about currents, and shows navigation marks and maritime hazards such as shipping channels and military exclusion zones that will not appear on a map. This imaginary chart extract shows an area with unusually strong tidal streams, as you can tell from the tidal stream arrow and the symbols marking powerful eddies and overfalls.
On a map the sea is shown in plain blue with no indication of depth, and only a hint about the places where sand or mud will be exposed at low tide. However a map is often more use than a chart. It shows the shape of the land very clearly with contour lines which join points of equal height. Where the contour lines are close together, the slope is steep. The shape of the land is also shown on this map by darker colouring for higher land, spot heights and conventional "shadows", and more information is given about land features. This makes it easy to identify a landmark such as a village, bridge, island, wood or mountain. If you can identify a landmark, you can easily find your own position at sea.
Kayakers and walkers seldom go long distances so they prefer their charts and maps on quite a large scale. 1:50,000 is usually fine for both. A 1:25,000 map will show more detail including rock outcrops, vegetation, paths, fence lines and campsites. A 1:25,000 chart has more space to show features and hazards that may affect small craft.
|Hiking, normal sea kayaking||1:50,000 (2 cm = 1 km)||1:63,360 (1 inch = 1 statute mile)|
|Mountaineering, kayaking in area with fast currents or complex topography||1:25,000 (4 cm = 1 km)||1:24,000 (1 inch = 2,000 feet / 0.379 land miles)|
|Detailed harbour plans||1:10,000 or larger||1:10,000 or larger|
A smaller scale of 1:75,000 scale (1.5 cm = 1 km) is less useful and your entire day trip may fit into a five-centimetre square. For many sea kayaking areas, charts are available only a 1:75,000 scale. See also Distances On A Chart.
Below you will see an extract from an Admiralty Leisure chart, reproduced by kind permission of the UK Hydrographic Office. It shows the tip of Pembrokeshire in Wales. This is an area with excellent scenery and wildlife, strong tidal currents which create challenging sea conditions, surf beaches, and plenty of nice pubs and walks if it's too windy for kayaking. It also has some truly exceptional hazards for the sea kayaker.
The scale of the chart is 1:75,000, and the extract is about one-thirtieth of it. On paper this extract is 16 centimetres wide. The area covered is a little over 6 nautical miles (11 kilometres) wide.
For a higher-resolution image, click here.
To the west you will see a dozen islands called the Bishops & Clerks. The South Bishop is one of the largest, and has just enough room for a lighthouse.
Most charts have a few tidal diamonds which are symbols printed in magenta that refer to a table in the margin. The table states the speed and direction of the tide at that location at various times. This chart has only two, neither of which appear on this chart extract. Both are near the mouth of Milford Haven for the benefit of oil tankers going to the oil refinery. Exceptionally, because there are very fast currents in the area covered by the chart extract, there is a tidal stream arrow. See the arrow halfway up the left side of the extract. The arrow has feathers, showing that it indicates the direction of the incoming tide at that location. It states that the flood tide flows at 2 knots during neap tides and 5 knots during spring tides.
The sea around the Bishops & Clerks and in the channel between them and Ramsey Island is littered with the twin wiggly lines that mean overfalls and tide rips. That's useful information for a kayaker, enabling you to avoid them either by a sprint across, by going at neap tides, or by crossing the channel at slack tide. In general, see Tides.
The most striking landmark is the St Davids lifeboat station at St Justinian, located just south of Point St John. It's a white building with a red roof which stands on high concrete legs and has a long, steep ramp for launching the lifeboat. The only sign of it on the chart is a small black symbol consisting of two cones stuck together end to end. (OK, it does look just like the Dagger Kayaks logo!)
The magenta box on the chart and the number 1482 indicates that UKHO also publishes a 1:25,000 chart covering only that area. This would be very useful for a kayaker making a first visit to this challenging region.
For more about what charts do show, see Features On A Chart.
Charts are intended mainly for use by ships and yachts so they have very little information about roads, car parks and paths, and they leave out many things which a kayaker would regard as a maritime hazard.
For example if a headland thrusts out a long way into the sea, it can create a small tide race or turbulent eddyline which is nothing to a ship but troubling to a novice or intermediate kayaker. Likewise, an underwater reef running out five metres from the tip of a headland won't be on the chart, but in a big swell it may unexpectedly create a breaking wave large enough to capsize or loop a kayaker. Another entertaining hazard you may encounter is the blowhole, in the form of a long thin horizontal tunnel into the base of a cliff. When the swell runs into one and fills it up, it may eject a horizontal jet of mixed air and water with the strength of a fire hose. Not on the chart.
An experienced sea kayaker who knows the speed of tidal currents in the area can look at a map or chart and accurately fill in a lot of information by guesswork. See the Reef Point illustrations at Kayaking On Fast-Moving Water.
The 1:75,000 Pembrokeshire chart extract we have used as our example does not show:
• The B-tches, which are either a serious hazard or a white water playspot depending on the state of the tide and your point of view. A line of little islands with shallow water between them, they are not named on the chart but appear as a green finger sticking out of the east coast of Ramsey Island. The green colour indicates that at very low tides you can walk dry-shod along the line of islands.
• The Horse Rock whirlpool, which is that very, very rare thing, a whirlpool that can take down a sea kayak. Horse Rock is not named on this 1:75,000 chart but it is shown as a tiny round dot in the middle of Ramsey Sound, just east of the deep water channel. The chart indicates that it is exposed at very low tides. Its drying height is marked as 0.9 metres above the level of the lowest tides. Note the ship wreck marked immediately alongside it.
•. Information about the shape and height of the land. It is often possible to identify an island or section of coast by its shape. On a map, relief is shown by contour lines, by different colours used for land of different heights, by symbols for cliffs, etc, and sometimes by overprinting shadows to give a three-dimensional effect. On a chart, the land is usually shown in one colour, and contour lines are either omitted or given only at intervals which are too large to be much use.
• The nature of the shoreline. You can't see them on the 1:75,000 chart, unless you use a magnifying glass and some imagination, but there are low to medium cliffs right round the coast except at Whitesands Bay and Porth Clais, with the occasional low-tide-only beach.
• Paths you could use to get up from the water in emergency.
• Most of the farms, camp sites and homes that might be useful in an emergency.
• The St Justinian car park and steps down to the beach.
• The Whitesands beach car park and café.
• The small town of St Davids, which surrounds the cathedral marked halfway up the right side of the extract.
For those things, you need to look at a 1:50,000 or maybe 1:25,000 chart alongside a yachtsman's or kayaker's pilot guide and the 1:50,000 Ordnance Survey map.