chartmaking. The first man to draw charts for seamen was probably Marinus of Tyre (c.70–130), though the periplus had been in use long before his time. He used an equidistant-cylindrical projection forming a grid of parallels and meridians, the mid-parallel and prime meridian passing through Rhodes, at that time the maritime centre of the known world. His proportion of the distances between parallels and meridians was four to five, giving an elongated appearance to the Mediterranean. Ptolemy (c.90–168), who laid the foundations of cartography, pays tribute to him in his Geographia and acknowledges his indebtedness to him in his own great work on the same subject.

Ptolemy was the first man to devise a projection whereby a portion of the surface of the spherical earth could be depicted on a plane surface (see plain sailing). His first conical projection, covering the known world in 180° from west to east, had meridians every 10° converging on the pole, the point of contact of the cone providing a curved parallel through Rhodes centred on the pole, while two similar parallels passed through Meroe and Thule, the furthest known southerly and northerly places respectively. He also developed a projection giving a curvature to all meridians except the centre one while the parallels also remained curved. On this projection he drew a world map showing the Mediterranean with some accuracy, and England, Scotland, and Thule in the north. Africa appears as a vast continent stretching across the south of the Indian Ocean, making it an inland sea, and continuing northwards to join Asia. From this map it is clear that Ptolemy did not believe, as Herodotus had written, that Africa had been circumnavigated.

Though, in the middle of the 12th century, the cartographer of the Islamic world al-Idrisi made a similar but more detailed map, Ptolemy's projections and maps were forgotten for a thousand years until they were discovered in Constantinople in 1400, brought to Florence, and translated from classical Greek into Latin. Many learned men came to Italy during the ensuing century to make translations of his works for their own countries so that during the 16th century many cartographers in Europe were aware of the Ptolemy world map and were trying to fit into it the new discoveries. The development of printing and engraving made possible the wide publication of such maps.

Renaissance Chartmaking.

The wind-rose and the magnetic compass were known to the 13th-century Mediterranean seaman, added to which he carried a portolano which gave him seamanlike guidance along the coasts. At the end of the 13th century what is now called the portulan chart appeared; sometimes they are known as ‘compass charts’ because magnetic compass roses, together with rhumb lines of direction extended from them, were set down at frequent intervals of the parchment area. The rhumb lines were used by the cartographer to measure bearings when laying down the coastline, and by the navigator for setting his course by pricking off from the rhumb line with dividers and a straight edge.

The prominence of Venice and Genoa during the Renaissance as two important maritime states provided the commercial demand which has motivated chartmakers throughout history. Later, the kingdom of Aragon, which included the ports of Palma, Barcelona, and Valencia, as well as those in Sicily, also became important cartographic centres. Then during the course of the 15th century Portugal, largely spurred on by Henry the Navigator, became predominant. Among those who went there to pass on their skills as chartmakers was the Majorcan cartographer Abraham Cresques (d. 1387), who produced the Catalan atlas of 1375. Influenced by the voyages of Marco Polo, this was a huge advance on earlier attempts to create a map of the world. For though Europe, North Africa, and Asia were still the only land masses to be depicted, Cresques had taken information from the early portulan charts so that the map is oriented to the north and the coastline of the Mediterranean is shown with great accuracy.

Early Portuguese explorations by sea, and the greater understanding of navigation they had achieved because of them, led to many more maps being made, the Fra Mauro c.1450—its exact date is not known—and the Genoese map of 1457 being among the most important. The former included information from Mediterranean and Arab seafarers, and, like the Catalan atlas, it also drew heavily on the voyages of Marco Polo. The Genoese map, by an unknown cartographer, draws much information about India and south-east Asia from the Venetian traveller Niccolo Conti, and from the rediscovered Ptolemy material.

Another great advance in cartography was the Cantino map of 1502. Gathered from the voyages of Vasco da Gama and another Portuguese navigator, Pedro Cabral (c.1467–1530), it included land masses never depicted before. The Indian peninsula, the entire African coastline, correctly oriented, and parts of the coasts of Brazil were all shown. Smuggled out of Portugal by an Italian, Alberto Cantino, it was available for study in Italy and was a huge influence on mapmakers for many years.

Around 1500 both Spain and Portugal established offices for controlling trade and exploration, the Casa da India in Lisbon and the Casa de Contrataçion in Seville, where up-to-date charts were kept and ocean pilots examined. In 1530 the King of Portugal appointed Pedro Nuñes (1502–78), a skilled cosmographer, to head his department of hydrography in the Casa da India, and it was to him that Portuguese navigators turned for a solution to the problem they found when trying to plot ocean courses on a plane portulan chart. Nuñes realized, and published the fact, that meridians converge towards the poles and that a course which crosses them at a constant angle is a spiral rhumb line leading to the pole.

North European Chartmakers.

During the 16th century the focus of map- and chartmaking moved to the Netherlands where, in 1570, Abraham Ortelius (1527–98) published his atlas Theatrum Orbis Terrarum which, among others, contained a significant map of the world. Using the prime meridian through the Canary Islands, the world is drawn in a projection developed directly from that of Ptolemy, but showing the full 180° both to the west and to the east of the prime meridian. All the new discoveries are shown, giving a good picture of the land masses of the world in general. It also included a vast continent encircling the southern portion of the world named ‘Australis Nondum Cognita’—called, on some later maps, Terra Australis Incognita—a vestige of Ptolemy's concept. It was a mystery that eluded explorers for another 200 years until James Cook eventually disproved its existence.

The previous year, 1569, Gerardus Mercator (1512–94) had published a new world map in eighteen sheets. With this he abandoned Ptolemaic theories and introduced his own projection where parallels of latitude and meridians of longitude cut each other at right angles so that a rhumb line drawn on it appeared as a straight line, so solving the problem of steering ocean courses which Nuñes had described 40 years earlier. However, it was not until the end of the 16th century that an Englishman, Edward Wright (1558–1615), made clear to seamen the benefits of Mercator's projection, describing it in his book Certaine Errors of Navigation Detected and Corrected (1599) with the aid of a diagram of great clarity.

But the problem of measuring longitude at sea simply was still a long way from being solved, so newly discovered lands were plotted on the charts with little east/west precision. The Board of Longitude was formed to find a solution, one eventually brought about by the accurate timepieces produced by John Harrison (1693–1776). Cook carried an early copy of Harrison's No. 4 chronometer, Kendall's No. 1, on his second Pacific voyage in 1772, and testified to its excellence in keeping time accurately, and hence its precision in obtaining a correct longitude.

Waggoners.

North European navigators had never felt the same need for charts as did the explorers from Spain and Portugal. Instead, they relied upon courses between one cape and another which had been handed down to them by their fathers, and on the use of the lead line to warn them of shallow water. However, in 1582 a Dutch seaman, Lucas Janszoon Wagenaer (c.1534–1605), impressed by Ortelius' maps, and having seen the portulan charts carried by the Portuguese traders on their voyages to Flanders for wool, began to compile a pilot book for western Europe. This finally developed into Spieghel der Zeevaerdt, a manual of navigation, a pilot book, and a series of charts for navigation from the Zuider Zee to Cadiz along the coast of northern Europe. It was published in two parts in 1584–5 and the then Lord High Admiral of England was so impressed with it that he commissioned a translation, and this was published in 1588 as The Mariner's Mirrour. These charts were widely used by British seamen for a century, calling them ‘waggoners’, a corruption of Wagenaer.

Over-reliance on the Dutch waggoners led Samuel Pepys, then secretary of the Admiralty, to commission a naval officer, Greenvile Collins (d. 1694), ‘to make a survey of the sea coast of the Kingdom’ in 1681. This was the first comprehensive survey of the British coast ever made and when it appeared as Great Britain's Coasting Pilot in 1693 it also was generally known as a waggoner. The name was even used for a sea atlas of the Pacific, Wagoner of the Great South Sea. This was redrawn by William Hack (fl. 1670–1700) from a Spanish derroterro captured by the buccaneer Bartholomew Sharp in the South Pacific during Sharp's voyage there in 1681–2. Hack's atlas is in the King George III Maritime Collection at the British Library.

Wagenaer's charts still owed much to the portulan chart, as did Collins's. Nevertheless, they began to take on a more seamanlike look with soundings reduced to a mean level datum shown in anchorages and over harbour bars, and with sketches to assist recognition of the coast. Standard symbols were also introduced to show safe anchorages, buoys, and submerged rocks, and these have survived on charts to the present day.

French Chartmaking.

Neither Wagenaer's charts nor Great Britain's Coasting Pilot had used Mercator's projection but Le Neptune françois, also published in 1693 on the orders of Louis XIV, did. The newly established Observatoire de Paris had been founded to bring about a better understanding of the celestial sphere and it was here that a method of finding longitude by the observations of Jupiter's satellites was devised. Once the latitude and longitude of the observatory had been fixed, a triangulated survey of the whole of France was made, relating stations along the whole coastline to the prime meridian of Paris. The charts in Le Neptune françois, were based on this triangulated survey, employed Mercator projection for the smaller scales, and were beautifully engraved. They showed a distinct advance over both the Dutch and British charts, and gave France a clear lead in chartmaking. However, the first comprehensive collection of charts to use Mercator projection was the Arcano del mare, published in three volumes in 1645–6 by the Florence-based Englishman Sir Robert Dudley (1573–1649).

The Dépôt des Cartes et Plans de la Marine was established in 1720 and through this office during the 18th century further editions of Le Neptune were published, culminating in 1764 with the official publication of the cartographic masterpiece Le Petit Atlas maritime. Produced by Jacques Bellin (1703–72), who had published a chart of the Mediterranean in three sheets in 1737, these were beautiful, clear-cut charts covering the greater part of the navigable world. Both publications were of a standard of clarity and accuracy not previously achieved anywhere and mark Bellin out as an outstanding cartographer of his day.

Triangulation Adopted by the British.

The use of a measured baseline from which a shore triangulation of fixed stations could be extended had reached Britain from France by the middle of the 18th century and was used to survey the Orkneys, and the west coasts of Scotland and Wales, and of Ireland, which was carried out for the Admiralty by Murdoch Mackenzie (b. 1712). In retirement, and when his nephew of the same name had taken over the coastal surveys, he devised an instrument, subsequently named a station pointer, for plotting the position of a ship or boat with reference to three triangulated points onshore, the two angles between them having been observed simultaneously by two men on board. In those days these angles were taken with Hadley's quadrant used horizontally; subsequently replaced by the sextant, this method of station pointer fixing lasted well into the 20th century and accounts for the rapidly increasing number of soundings appearing on charts throughout the 19th century.

Early American Chartmaking.

Contemporaneously with the work of the Murdoch Mackenzies, Joseph des Barres (1721–1824) and others working in support of the British Army in North America were making detailed coastal surveys of the east coast. Their work resulted in the publication by the Admiralty of the atlas Atlantic Neptune in 1777, the name of the Roman god Neptune being often used in titles during the 18th century to describe collections of maps and charts, in much the same way as atlas. Beautifully engraved, using more symbols, and having extensive sounding coverage, this magnificent collection of charts recaptured from the French the ascendancy they had held since the beginning of the century, and served as the primary source for most North American charts for 50 years after the birth of the USA in 1783.

In 1807 the US Congress authorized President Jefferson ‘to cause a survey to be taken of the coasts of the United States, in which shall be designated the islands and shoals, with the roads or places of anchorage, within 20 leagues of any part of the shore of the United States, and also the respective courses and distances between the principal capes, or head lands, together with such other matters as he may deem proper, completing an accurate chart of every port of the coasts within the extent aforesaid’.

It was not until 1816 that the Swiss-born Ferdinand Hassler was appointed superintendent of the survey of the coast but by 1836 the organization had become a flourishing agency called the US Coast Survey, the Federal government's oldest scientific agency. In 1871 a geodetic connection between the coastlines of the Pacific and Atlantic oceans was authorized which resulted in the agency being renamed the US Coast and Geodetic Survey in 1878, a name now retained by an office within the National Ocean Service, a part of the National Oceanic and Atmospheric Administration.

Chartmaking in the 19th–20th Centuries.

By 1800 virtually the whole of the inhabited world appeared on charts and world maps. Cook had finally disproved the supposed existence of Terra Australis Incognita, first drawn by Ptolemy 1,500 years earlier, and had put New Zealand on the map; Flinders had laid down the coasts of Australia; and Vancouver and others had delineated both shores of the North Pacific. Theirs were coastal running surveys, largely laid down from shipboard observations. The 19th century was devoted to detailed charting of bays and anchorages, passages, and approaches along every distant coastline. In this work the surveying service of the Royal Navy played a prominent part, and the first chart produced by the Admiralty from its own surveys was published in 1800.

An explanation of the construction of a gnomonic chart, on which a great circle sailing course appears as a straight line, first appeared as early as 1669, but it was not until Hugh Godfray published two polar gnomonic charts in 1858 that they became popular with mariners. Together these covered the greater part of the world, one for the northern, and the other for the southern hemisphere.

For a short period in the early 19th century when surveys were largely exploratory, surveyors were encouraged to send in drawings of their work fit for direct engraving, but soon it became necessary not to limit the surveyor in this way. Instead the Admiralty's hydrographic department, which had been established in 1795 under Alexander Dalrymple (1737–1808), was made responsible for converting his detailed work into what the navigator required, including the choice of scale for publication. Scale is subject to the dimensions of the projected chart and there has always been pressure for a standard size which would be practical in use, convenient for chart table and folio covers, and simplify the printing from, and the handling of, chart plates. A size of 965 × 635 millimetres (38 × 25 in.), known in the paper trade as double elephant, has been the most used, halved for smaller charts. The internationally accepted maximum size is 71 centimetres by one metre (28 in. × 40 in.).

In 1828 the Admiralty's Hydrographic Department published its first Sailing Directions, and in 1832 the promulgation of new information to keep charts up to date was begun in the Nautical Magazine. Two years later the issue of Notices to Mariners began for urgent items, and in 1907 paste-on reproductions of affected portions, known as ‘block notices’, were issued to facilitate corrections, a method the Japanese had begun in 1904. By the late 1960s there were some 3,000 notices every year which had to be entered on existing charts to take account of changes.

Traditionally there were three steps before the publication of a chart: a drawing based on a surveyor's work or a foreign chart; its engraving or inscription on copper or lithographic stone; and printing. A chart was originally judged for accuracy by the number and spacing of the soundings it showed; later it relied more on depth contours with fewer supporting depths and made more use of colours for depth differentiation. Depth lines, too, were simplified to speed reproduction stages. The representation of land features also changed, particularly in the hill-work. This went through stages of hachuring, perhaps accompanied by ‘smoke shading’, to the use of contours as on a land map. One reason for this was the introduction of radar; another was simplicity in reproduction.

From 1939 the development of hyperbolic navigation called for a new family of charts in which hyperbolic graticules were superimposed in colour on the navigational detail. Among other problems this involved was the adaptation of the reproduction process so as to ensure the accurate registration of the various printing plates. After the Second World War (1939–45) other developments in chartmaking included using chart plates made from plastic instead of copper or lithographic stone, and using metric measurement for depths instead of fathoms, a change which started in the late 1960s. See also deep scattering layers. Whitfield, P. , The Charting of the Oceans: Ten Centuries of Maritime Maps (1996).

Modern Chartmaking by Adam Kerr

Chartmaking underwent a major change with the introduction of computer technology in the 1960s. Initially, the term ‘computer-assisted cartography’ was used—perhaps to stress that man had not been left out of the process entirely—with computers used to draft chart borders and grids, which had been previously a laborious undertaking. Another task that lent itself readily to early computer calculation was the lattices used for plotting hyperbolic navigation coordinates.

Nowadays most of the work is done by computers, although there are still important areas where the skills of the trained cartographer are essential. It is vital in the use of computers that all the data is in digital form. All modern surveys provide it, but historic data from graphic sources must be converted.

It is not always appreciated that the information appearing on a printed chart is a very small part of that obtained by the field surveys, which with modern systems collect huge quantities of data. It requires great skill to reduce this mass of information into something that the navigator can assimilate quickly and accurately. Efforts are currently being made to develop computer programs that will tackle this task.

Efforts, which have given rise to much debate, are also being directed towards finding suitable programs to calculate and draw depth contours, which are more numerous on modern charts than they were previously. More exotically, research is also in hand to show the configuration of the seafloor as a coloured three-dimensional image.

Chartmaking has traditionally tended to build a margin of safety for the navigator when interpreting the information received. For instance, all depths are shown as measured from the extreme low tide plane, so that the navigator has the height of the tide as a margin of additional depths. However scientists studying oceanography and other aspects of the sea are more interested in the best interpretation of the actual depth.

Digital Charting.

Traditionally printed paper charts have been used as the medium for plotting navigation. However, in the early 1980s interest developed in not only processing the hydrographic data digitally, but presenting it to the navigator in digital form that could be fed into an Electronic Chart System (ECS) that would display all the information on a computer monitor. Not only is the chart information displayed on screen but the ship itself is positioned continuously on the chart. This is a great help to the navigator, leaving him with his hands free while being able to monitor constantly the location of his ship. Such systems are being increasingly used, though paper charts are still common.

The capabilities of this technology have led to increased sophistication, not only in what basic chart information can be shown, but also in layers of other information, such as ice or other marine meteorological conditions. Specifications for the advanced systems that have these capabilities, called ECDIS (Electronic Chart Display and Information Systems), have now been approved by the International Maritime Organization (IMO). Unlike ECS, where paper charts still have to be carried, ships are legally permitted to use ECDIS without them, but it is a costly and complicated system, and tends only to be used on large vessels.

Oceanic Cartography.

While the main focus of chartmaking has been to provide nautical charts for the purpose of navigation, there has always been a need by ocean scientists to plot and display numerous forms of data concerning the oceans. During the 18th and 19th centuries there had been a number of individual initiatives to develop ocean maps to show oceanographic phenomena. Perhaps the best known of these is Matthew Maury's Physical Geography of the Sea which was published in 1855. However, towards the end of that century a group of eminent oceanographers met at the 7th International Geographic Congress at Berlin to discuss the need for a bathymetric map of all the world's oceans, bathymetric meaning the sounding of the seas. As a result, a major mapping project, called the General Bathymetric Map of the Oceans (GEBCO), was initiated to map the topography of the seafloor. This celebrated its 100th year in 2003.

Besides the topography of the seafloor, many other types of data are also mapped. This can include geophysical data such as gravity anomalies or magnetism or chemical or biological parameters. Frequently the maps are bound together as atlases so that comparisons of different parameters can be easily made.

Cartographers preparing oceanographic charts (or maps) will be generally less bound by navigation requirements, such as the general use of the Mercator projection that is used to show a ship's course as a straight line when plotted. Instead they may wish to use projections such as Equi-area, which shows all parts of the earth in strictly equal area, i.e. there is no distortion as in the Mercator projection. It has already been said that oceanic cartographers aim to show features in the most accurate form they are able, but as the data may sometimes be limited, very considerable interpretation is sometimes used. As the navigational chartmaker has moved to digital presentations, so also have the oceanic cartographers, who today make considerable use of mathematical models and digital displays on computer monitors. Black, J. , Visions of the World: A History of Maps (2003).
Scott, D., et al. (eds.), The History of GEBCO, 1903–2003 (2003).