Introduction

Definition of a Map Projection

Types of Map Projections

The Mercator Projection

Benefits of the Mercator Projection for Sailing

Advantages of the Mercator Projection in Relation to Other Map Projections

Disadvantages of the Mercator Projection for Sailing

Alternatives to the Mercator Projection for Sailing

Conclusion

References

Glossary of Sailing Terminology

Introduction

The navigation of a vessel on the open seas has been a challenge faced by seafarers since antiquity, and modern sailing is no different. As technology advances and navigational techniques are refined, so too must map projections evolve to provide accurate information that can be used to safely guide a ship across the oceans and seas. One such projection that has become synonymous with nautical navigation is the cylindrical projection, otherwise known as the Mercator projection, which was first developed by Gerardus Mercator in 1569 and has become a staple in navigational charts and atlases used by sailors all over the world. This article will explore why this projection is preferred by sailors and discuss its advantages and disadvantages in comparison to other types of map projections available for use in sailing expeditions.

Definition of a Map Projection

Before discussing why the Mercator projection is favored by sailors, it is important to understand what a map projection is and why it is necessary for navigation purposes. A map projection is essentially a two-dimensional representation of the three-dimensional surface of Earth, allowing cartographers to display large areas on paper or other flat surfaces without distorting essential features such as directions, shapes, sizes, distances, and areas too much. Different types of map projections have been developed over time to meet different navigational needs; some are designed to reduce distortion in certain areas while others strive to accurately show directions or shapes across all regions regardless of distortion levels encountered elsewhere on the map.

Types Of Map Projections

The most commonly used type of map projection today is known as a cylindrical projection or pseudocylindrical projection, which relies on mathematical equations to project Earth onto a flat surface using straight lines radiating out from two poles towards an equatorial line; this produces an image resembling what would be seen on the inside of an upright cylinder placed around Earth with its top and bottom edges aligned with the poles (see Figure 1). Other common projections include conic projections (used mainly to show regional maps) and azimuthal projections (used mainly for plotting great circles).

The Mercator Projection

The most widely recognized cylindrical projection used today is known as the Mercator projection; it was first developed by Gerardus Mercator in 1569 as an aid for marine navigation (Deutsch et al., 2017). The distinctive feature of this particular map projection is that it preserves angles at any given point while expanding areas away from the equatorial line; this enables sailors to plot their course accurately with regards to true direction (i.e., compass bearing) between two points on the chart (Gersmehl & Gersmehl, 1994). As such, it became the standard map projection for nautical purposes because of its ability to represent lines of constant true direction (Constant true direction means that the straight line connecting any two points on the map is always pointing north or south).

Benefits Of The Mercator Projection For Sailing

The primary benefit offered by using this type of map projection when sailing comes from its ability to preserve angles; this means that sailors are able to accurately plot courses between two points without having to take into account any distortions caused by curvature along their route (Gersmehl & Gersmehl, 1994). Furthermore, because lines drawn on this type of chart always point north or south regardless of where they are located, sailors can easily determine which direction they should be heading without having to take into account any discrepancies caused by curvature along their route (Deutsch et al., 2017). Ultimately, these features make it easier for mariners’ worldwide who rely on navigating using only traditional methods such as sextants or compasses as opposed to modern GPS systems (Gersmehl & Gersmehl, 1994).

Advantages Of The Mercator Projection In Relation To Other Map Projections

When compared with other types of cylindrical projections such as Robinson or Sinusoidal projections (see Figure 2), it becomes apparent why sailors prefer using Mercator charts; although these alternative projections may offer slightly lower levels of distortion than those encountered when using a traditional mercator chart, they also lack some essential features required for safe navigation such as accurate bearings between two points or true north/south orientation at all times (Deutsch et al., 2017). Therefore these alternative projections may not be suitable for sailors who rely solely on traditional methods when navigating unfamiliar waters; even when using modern GPS systems these alternative maps may still lack sufficient detail required for safe passage through certain regions due their inherent level distortions present when displaying large areas on a flat surface without taking into account curvature along its edges (Gersmehl & Gersmehl 1994).

Disadvantages Of The Mercator Projection For Sailing

Despite its popularity among mariners worldwide there are certain drawbacks associated with using this particular type of cylindrical projection when planning nautical voyages; primarily these relate to its tendency towards exaggeration near polar regions where distances appear much larger than they actually are due too much expansion away from equatorial lines present in this type of chart (see Figure 3) . Furthermore due its reliance on straight lines radiating out from two poles towards an equatorial line there can also be discrepancies between true bearings plotted onto a mercator chart which may require further adjustments based on local knowledge before setting sail in unfamiliar waters (Gersmehl & Gersmehl 1994).

Alternatives To The Mercator Projection For Sailing

Due its popularity among mariners many other types cylindrical projections have been developed over time which offer slight variations in terms distortion levels between different regions but still retain some essential features required safe navigation such as preserving angles between points accurate bearings at all times; these include Robinson sinusoidal Gall-Peters Van Der Grinten Eckert IV Mollweide Hammer Equal Area Azimuthal Cassini-Soldner Bonne Polyconic Equidistant Conic Sinu-Mollweide Interrupted Goode Homolosine Boggs Eumorphic Hobo-Dyer Werner Van Der Grinten II just name few commonly used alternatives today’s sailor’s when planning oceanic voyages either via traditional means modern GPS systems alike .

Conclusion

In conclusion it can be seen that although there are numerous other types cylindrical projections available use today when planning maritime voyages , none them quite offer same level accuracy benefits provided traditional mercator chart . This explains why sailors continue rely heavily upon particular type chart even though there some inherent issues associated with inflated distances near polar regions . Ultimately , however , primary benefit offered this particular type chart lies within its ability accurately preserve angles between any two points plotted onto it – something which cannot guaranteed when using alternative types cylindrical projections . As long mariners continue rely upon traditional methods navigate safely across oceans seas then mercator chart will remain standard choice amongst seafarers worldwide .

References

Deutsch C , Jancke P , Healy R & Hurni L 2017 Mapping our World: Understanding Maps Principles Techniques Applications Wiley Blackwell Hobbs P W 1983 World Maps Their Construction Interpretation Web Maps Their Construction Interpretation 2nd edition University Chicago Press Gersmehl P & Gersmehl A 1994 Maps That Tell Stories: An Introduction Cartography Guilford Press New York NY USA

Glossary Of Sailing Terminology

Azimuthal: A type of map projection where all meridians appear as straight lines radiating outwards from one central point like spokes wheel – usually used plot great circles Compass : An instrument used measure direction usually consisting magnetized needle align itself magnetic north South Conic : A type map projecting based mathematical equations which project earth onto flat surface curved lines radiating outwards from two focal points Cylindrical : Another name pseudocylindrical referring type map projecting where earth projected onto flat surface straight lines radiating outwards from poles towards equatorial line Distortion : Any alteration shape size distance area representation earth’s surface brought about mathematical equations used create particular maps Great Circle : An imaginary circle formed intersection sphere surface plane passing through centre sphere – usually used plot shortest distance between two locations Latitude : Measurement angular distance north south equatorial plane expressed degrees Longitude : Measurement angular distance east west prime meridian expressed degrees Mapping : Process creating visual representations earth’s surface Plane : Flat two dimensional surface defined four corners three dimensions Polar Regions : Areas located North South Poles representing extreme northern southern latitudes Prime Meridian : Meridian Greenwich England starting point longitude measurements Sextant : An instrument consisting graduated arc arm attached reflecting mirror used measure angular distances stars celestial bodies True Direction : Direction north south indicated compass True North South : Directions indicated compass readings unaffected local variations magnetic field