One of the easiest ways to fix your position is to sail up alongside a charted object. Buoys are the obvious choice, but remember that they can be relocated, especially in areas of shifting sand or mud banks. Keep your charts up to date, and where possible choose an object firmly fixed to the seabed. Grab your chart, make a cross next to the object, note the time and log reading, and you’re done.

Dead Reckoning (DR) Position is the position of the ship solely based on its last known position, course, and speed over a given period without taking into account external factors such as wind, current, or other navigational influences. A previously determined position can also be termed as a fix; the estimated speed and the course are applied to that fix to obtain a DR. A DR position should be made every time when there is a change in course and/or speed, the DR position must be plotted afresh. If the predicted course line is judged to be/proofed to be incorrect, plot the DR once again for the corrected data. Do not draw a new course line from an Estimated Position (EP). Always plot a new course line from a fix

The Running fix is not particularly accurate, but provides a useful fix if landmarks are scarce. If there’s only one suitable charted object in sight, and you can’t determine your range using a depth contour, given time you can find your position using a running fix. This is often the case at night, when your choice of objects from which to take bearings are limited to those that are lit. This method is most appropriate when your voyage is more or less parallel to the coast. There is a need to follow the procedure for this fix carefully to ensure the best outcome.

Estimated positions are essential for maintaining a record of a vessel's progress, especially during long passages when visual references may be limited. By plotting estimated positions regularly, navigators can ensure they remain on course and avoid hazards, particularly in challenging conditions or when visibility is poor. In summary, understanding and accurately calculating an estimated position is vital for effective navigation, allowing mariners to make informed decisions about their course and safety at sea. It is determined using the vessel's last known position and accounting for various factors that may affect its movement, such as: Course Steered: The direction in which the vessel is heading. Speed of the Vessel: How fast the vessel is moving. Time Elapsed: The duration since the last known position was recorded. External Influences: Factors like wind (leeway) and tidal currents that can cause the vessel to drift from its intended course

Transits are formed when two charted objects are in line. They are often found marked on charts, or in pilot books, to give a clearance from a danger or a safe entrance into port. Transit: Single This provides an accurate line of position and gets you halfway to an accurate fix – you just need to find where you are on the line.

Transit: Crossed The best way to find your position on a transit is to find another one which crosses it, ideally at about 90°. This is a tremendously accurate way to fix your position, but you generally need to plan the fix beforehand, so it’s often used to give an accurate fix for starting a passage. The easiest way is to find charted transits, or objects on the chart which form suitable transits. Then, to get to the planned position, pick up one of the transits and sail along it until the other transit marks come into line.

Transit: With bearing A river entrance transit crossed with a bearing at roughly 90°. In the absence of another transit, a bearing on a fixed object provides a good fix. Always try to choose an object which lies at roughly 90° to the transit – shallow angles of intersection create greater errors.

Plot your first position line, this is the first bearing to our known reference object. We are somewhere on this line, but do not know where. Plot our second position line after a period of run time, during which we have ideally passed the abeam of the known object, we take and plot a second position line to the same object. We are now somewhere on this line. Two or more intersections among position lines give us a relatively accurate position of the vessel. The optimum angle of intersection between two position lines is 90 degrees

Fix: 3 points When choosing three charted objects, maximising the angles between them to minimise error. Lighthouses and buildings are the ideal choice as they don’t move and are easy to sight through the compass. Take bearings as quickly as possible, noting them down as you go and leaving the one most abeam until last – this bearing changes the fastest. Then plot them on the chart. Unless you have a stationary boat and extraordinarily steady hands the lines will not intersect perfectly, instead coming together in a triangle called a ‘cocked hat’. Your true position could be anywhere within this triangle, so the smaller it is, the more accurate your fix.

All radars are equipped with a variable range marker (VRM) and an electronic bearing line (EBL). These allow you to obtain an accurate fix from a single object. Placing the electronic bearing line on an object will give you its bearing, relative to the ship’s head, and the VRM will give its range. By adding or subtracting the bearing from the compass course, depending on whether to object is to starboard or port, and correcting for deviation and variation of the ship’s compass, the bearing can be drawn on the chart and intersected with the range to give an accurate position by day or night. Intersecting ranges give two positions, but it’s usually clear which one is valid. Another way to obtain your position by radar is to use the Variable Range Marker to find the range of two objects (Racons are ideal). This avoids any calculation at all: simply find the two ranges and draw them on the chart with a pair of compasses, using the charted object as the centre. The resulting circles will intersect in two places, giving two possible positions. However, it’s usually obvious which is correct – the false one is often on land! If there is any doubt, a rough bearing will clear up the ambiguity.

A depth contour may be the first useful position line available when making landfall. The echo-sounder has of late become simply a tool to prevent you running aground, but in conjunction with the chart it can be a useful source of position information. To use the echo-sounder for position, you need to know the current height of tide. It is clear on the chart contour lines to show various depths which you will cross Checking when you go over such a contour line and having a bearing on a known object that will plot your position.