The Mapmakers: An essay in four parts

16th-century mapmaking

Maps (of land surfaces) and charts (of sea coasts) are scaled down representations of the earth's surface. For this reason they are ideal documents to prove that a discovery has taken place and provide the means for the exploration to be repeated by others.

Maps are made up of three measurable elements: location, direction and distance. On some maps symbols and elevation are added. Symbols give more meaning to locations while elevation adds altitudinal distance. The precision of these elements and their exact placement on maps relative to each other, is what separates accurate maps from poor ones. Accuracy is dependent on:

  • the precision of the instruments available to make observations,
  • the observer's knowledge of the earth's shape and size, and its relationship to various celestial bodies,
  • the number of precise observations that form the basis of the map,
  • advances in the nature of mathematics used to make observations and render these into maps, and
  • the skill and training of the observer.

By the 16th century there was a general agreement that position be recorded by latitude and longitude. Due to the unvarying relationship between the earth's axis and the sun and stars, latitude (the angle between a place, the centre of the earth and the equator) could be easily calculated. This was done either by measuring the height of the sun at noon above the horizon and correcting that observation for the day of the year (sun's declination); or, by measuring the height of the North Star (Polaris) and compensating slightly for the difference between the position of Polaris and the geographic pole, since the two do not exactly coincide. To do these tasks two instruments could be used; the astrolabe, mainly used for measurements on land, and the cross-staff (also called Jacob's Staff) for observations at sea.

Sixteenth century measurements of latitude such as Jacques Cartier's were accurate to about one-quarter to one-half of a degree (one degree latitude equalling about 111 km). Longitude, the angle between a place, the earth's axis and a prime meridian (today the prime meridian is the longitude of Greenwich, England), was impossible to calculate accurately until John Harrison invented the marine chronometer, (a large pocket watch set on Greenwich mean time) in 1773. Since the ancient Greeks, geographers had known that longitude could best be determined by calculating the difference in solar time between two places. Since the earth is 360° in circumference and rotates on its axis every 24 hours, one hour of time equals 15 degrees longitude. One degree therefore, equals four minutes of time and about 111 km at the equator. Since time-pieces were not generally available until late in the 18th century, longitude had to be obtained by estimating east-west distances from a place of departure to a destination. On land, distances were estimated by travel time -- for example the distance an average man could walk in an hour (one league or about five kilometres). The French called this the "lieu d'une heure de chemin." Similarly, at sea, the estimated speed of a ship was converted into distance. This was called "dead reckoning." A navigator kept very careful note of all his speeds, course changes, encounters with currents, etc. in a log book. At the end of the day, he would convert all his observations into distances and plot them on his chart according to his compass observations.

By the 16th century, the mariner's compass was in general use. It was divided into 32 "points" or "winds", rather than degrees. Each point was equal to 11°15'. Compasses were not accurate enough to sail by degrees. Since a compass points to the magnetic pole and maps are on the geographic pole (true north) compasses had to be corrected for this difference (magnetic declination). In the 16th century, few mariners knew how to do that, or considered it to be unimportant. Nor did many know that magnetic declination varied across the earth's surface and that it changed over time (variation). A result of all this confusion was that compass bearings on 16th century maps tended not to be very accurate. Most were in fact magnetic bearings, giving these maps a peculiar orientation to modern readers.

Due to the twin problems of measuring direction and distance over the open sea, most 16th century navigators preferred to minimize guesswork through "parallel" (or "latitude") sailing. A captain would sail along the coast of Europe until he reached the latitude of the place he wanted to go to. He would then depart the European coast and use the one instrument he trusted, his cross-staff, to stay on that latitude until he got to the other side. On this journey he would then have to estimate his distance along a relatively straight course. This distance would then become the distance between Europe and his destination on his map along the one line of latitude he had sailed.

By means of a table calculated by mathematicians for every line of latitude (parallels), the navigator could now mark off his lines of longitude (meridians). The more often he travelled over a route, the better his observations got. Once he reached his destination, he would sail within sight of the coast, taking compass bearings of the coastline and of prominent features, estimating distances and, weather permitting, calculating the latitudes of places. Bays, river mouths, hills, etc. were sketched on the chart as the ship sailed past them. These rough reconnaissance surveys formed the bases of most 16th century maps. Another method for calculating distance sailed was the rule 'to raise or lay a degree of latitude'. This was an early form of 'plane sailing' (using right-angled triangles) wherein a navigator would lay out a course with his compass. When he had crossed one degree of latitude by observation with his cross-staff (the adjacent side of his triangle) he could look up the distance he had sailed (hypotenuse of his triangle), and longitudinal distance traversed (side opposite his course angle), in a set of tables calculated by mathematicians. The invention of trigonometry made these tables redundant. It was not until the early 17th century, motivated by the search for harbours and locations for settlement, that more accurate maps were produced with better instruments.

17th-century mapmaking

During the early 17th century, mapmaking took a huge leap forward. The instruments had improved; mathematical and astronomical concepts necessary to making accurate measurements had evolved; observers were better trained; and -- very importantly -- strong motives had arisen to make accurate maps.

Before the close of the 16th century, English mathematicians had perfected triangulation (navigation and surveying by right-angled triangles) through plane trigonometry. This development allowed navigators to set courses on any compass angle and permitted surveyors to produce much more accurate surveys on land. Although the mariner's compass remained in use, most compasses were now manufactured to read in degrees as well as points, permitting finer observations and the use of trigonometric tables. The better seamen learned how to correct their compasses for declination and early in the century the English had determined the existence of annual compass variation.


Latitude determination was greatly improved with John Davis's invention (ca. 1595) of the back-staff (Davis quadrant). It was further developed over time and remained unsurpassed until the invention of John Hadley's reflecting quadrant (1731). The measurement of distance sailed at sea was improved by another English invention, the common log. This device was a line, knotted at fathom (six foot) intervals and attached to a float. The speed of a ship was calculated by heaving the float off the stern and counting the knots as they ran through the navigator's hands during an interval of 30 seconds or a minute. The result was converted to distance over the time the wind speed was constant -- a great improvement over dead reckoning.

Longitudinal distance between Europe and Canada was determined by solar and lunar eclipses. A predicted eclipse would be timed in some European city (usually Paris or Rome) and at Québec. The difference in time between the two observations was calculated and converted to degrees at one hour per 15 degrees. This was an exacting procedure, but good results were obtained by the Jesuit Bressani in the 1640s and by Jean Deshayes in 1686. With fairly accurate surveys in Europe to determining the absolute length of a degree of latitude, and a decree being made by Louis XIII in 1634 to create for the first time a standard prime meridian for French maps (at Ferro, in the Canary Islands), the basic grid of the modern map began to take shape.

What lagged was the education and inclination of navigators and surveyors to take advantage of such innovations as triangulation, more precise compasses, the back-staff, and the common log. In this respect, England moved ahead much faster than other nations with the establishment of training centres for navigators late in the 16th century. In Quebec, in 1661, Martin Boutet became the first person appointed to teach applied mathematics at the Jesuit college. In 1666, the intendant, Jean Talon, broadened this appointment to include the teaching of navigation and surveying. Boutet was succeeded by Jean-Baptiste-Louis Franquelin in 1687 and Jean Deshayes in 1702. These were competent men who trained Canada's pilots, navigators and surveyors -- all of them mapmakers.

Early in the 17th century the French had decided to settle Canada and the English to explore a northern passage to Cathay. Both these interests required accurate mapping. In the North, men like Foxe, James and, especially, Baffin, were trained in the latest methods of producing accurate reconnaissance maps. In New France, Champlain prepared the first chart of the Atlantic coast to Cape Cod between 1604 and 1607, including potential harbours, using triangulation. From the first of two anchorages he would take compass bearings of a series of prominent features, then move his boat over a carefully measured distance to the second anchorage and take a second set of bearings of the same features. Each feature was now at the apex of a triangle of which he had the three interior angles and the length of one side. Triangles produced this way were transferred to a chart and the shoreline sketched in. Champlain did not understand trigonometry, but later mapmakers who did used the same principles and were able to make their maps more accurate than his. On land, the first property surveys and maps of the St. Lawrence shore were undertaken by Jean Bourdon with a combination refracting telescope and compass, a gift of the Jesuits. This forerunner of the theodolite permitted Bourdon to make accurate surveys with triangulation.

Explorers who travelled into the interior west of Montreal, first obtained Native maps and guides. These Native maps rarely appeared on French maps unless they were of areas the French had not yet seen. As the French advanced west, they made their own maps. Between Champlain's last map (1632) and the late 1670s the best maps were made by -- or based on the observations of -- the well trained and inquisitive Jesuits. The basic ingredients of these maps were latitude, compass readings and estimates of distance. The information that came out of La Salle's explorations and others toward the end of the century was, in some respects, not as good. While maps of the Atlantic coast and that of the St. Lawrence were achieving some accuracy, those of the interior west of Montreal were essentially rough reconnaissance maps. Notable on maps of the time, because they were of interest, were the lakes and river systems that served for transportation and the location of Native groups who were important as military allies, suppliers of furs and targets for missionaries.

18th-century mapmaking

The trends of the 17th century became realities in the 18th. Advances in technology, general acceptance of new mathematical and astronomical theories, and rigorous training schools for navigators and surveyors had an increasing impact on the accuracy of maps.

In New France, escalating tensions with England prompted renewed hydrographic surveys of the Atlantic coast and the Gulf of St. Lawrence by Testu de la Richardière (1730-41), Gabriel Pellegrin (1734-55) and Joseph Bernard Chabert (1750-51). In 1750, Chabert erected Canada's first observatory at Louisbourg for astronomical observations and the determination of longitude. Inland, the engineer Chaussegros de Léry, and his son of the same name, made good charts of the upper St. Lawrence through Lake Ontario to Detroit and Sault Ste. Marie. All of these men were competent marine and military surveyors using the latest methods (mainly triangulation) and instruments. The interior of New France did not fare as well since there were no trained surveyors on the La Vérendrye expeditions. Their maps were, in fact, redrafted Native cartography.

After the mid 18th century, map accuracy increased, primarily due to the development and manufacture of new instruments and stringent training in how to use them. In 1731, John Hadley invented the reflecting quadrant (really an octant), which rapidly replaced the Davis back-staff for latitude observation. The sextant, a finer instrument, was developed out of the octant in 1757. It came into common use before the end of the century and remained in use well into the second half of the 20th century. The invention of the artificial horizon (a box of quicksilver), by George Adams in 1738, made latitude observation possible on land where the real horizon was not visible. The invention of the octant and sextant also made it possible to make reasonably good calculations of longitude by lunar distance, a method invented by David Maskelyne in 1761.

The construction of good high power refracting telescopes made another, older method of longitude calculation possible, by observing predicted eclipses of Jupiter's moons. In 1766, tables based on the Greenwich meridian and showing lunar distance and the locations of Jupiter's moons were printed in the Nautical Almanac. These two methods required a great deal of skill and an up-to-date Almanac. It was not until John Harrison invented the marine chronometer and it was tested on James Cook's second voyage (1772-75) that the problem of longitude calculation was solved. The first use of the chronometer in Canadian waters was on Cook's third voyage in 1778. During the 1780s it was used in Newfoundland waters and reappeared on the West Coast with Vancouver's surveys (1792). That these were all British inventions helped to move that country to the forefront as a naval power.

The modern mapping of Canada began in 1778 when James Cook appeared on the West Coast and Philip Turnor was hired by the Hudson's Bay Company to train surveyors and to begin mapping the western interior. Inland surveyors such as Turnor, Fidler and David Thompson carried an octant or a sextant, modern compasses, an artificial horizon of quicksilver, a powerful refracting telescope and, if possible, the latest edition of the Nautical Almanac. Their methods were all similar, consisting of control points and estimated distances over a course laid out along compass bearings. Thompson, who surveyed some 20 800 kilometres of Canadian territory, would set up control points at prominent places for which he calculated latitude with his sextant and longitude by Jupiter's moons. From these points he laid out compass bearings, which he followed by canoe, by horse or on foot, estimating the distances he traversed. By repeating this process he established a grid of control points linked by compass bearings and estimated distances. Since distances had to be estimated, Thompson would adjust them through control points established with his surveying instruments. Hills and mountain ranges in Thompson's surveys were depicted by hachuring and the direction of river flow by little arrows. Other topographic detail was simply sketched in. Native encampments were often noted, and on his Columbia River survey Thompson even gave a population estimate for each of the Native villages he passed. These methods produced very good reconnaissance surveys.

In coastal charting, a marine surveyor such as Cook or Vancouver would keep a careful record of the course of their ship. Distances were calculated by means of a log, and prominent features along the coast were triangulated. It was essentially the same procedure used by Champlain, but often from a moving ship and with far better instruments. Surveys of an intricate coastline such as that of British Columbia were done by triangulation from rowboats, using beacons set on shore. Drawings were sometimes made of prominent features or a profile of the coast was sketched as it appeared from the sea. Surveying in the 19th century achieved greater accuracy through the common use of the chronometer and crews sent out with measuring chains and theodolites. Cadastral, boundary and railway surveys required a new kind of accuracy not found in earlier maps.

Map production

Map production went through a series of stages, beginning with the field observations of an explorer, a surveyor on land, or a hydrographer or navigator on water. In order to be useful for mapping, their observations had to contain as many precise measurements of distance, direction and location of latitude and longitude as possible. These field observations, in the form of notebooks, ship's logs and sketched maps, usually went to a professional cartographer, who was often also a geographer.

The process by which information moved from field observations made in Canada to maps produced by European cartographers and printers was systematized by the French well in advance of the English. In 1670 the intendant of New France, Jean Talon, ordered all explorers to keep records. Governor Buade de Frontenac added to this directive in 1674, by appointing Jean-Baptiste-Louis Franquelin as Canada's first cartographer, with orders to receive these records, construct proper maps and convey this material to the Ministry of the Marine in Paris. Between 1674 and 1708, Franquelin made some 50 maps. None were ever published, but they informed the Ministry and were made available to cartographers appointed by the court to construct maps. In 1716, Gaspard Chaussegros de Léry was appointed chief engineer at Québec, also assuming the job of chief cartographer. When the cartographic division was established in 1720 as a division of the Ministry, Léry's maps became accessible to its chief engineer, Jacques-Nicolas Bellin, whose cartographers and printers kept the maps of the French empire up-to-date.

Professional cartographers had access to earlier maps, other field observations, and different information as well as the technical competence to compile these into maps which placed new findings in a broader context. Cartographers producing maps of Canada were almost exclusively French and English and living in Europe, until map publishing became established in Canada during the 1820s.

The main problem for these cartographers was judging the accuracy of the information they received, since they were in no position to verify it. Before the use of mechanical means to reproduce maps, the cartographer's map would be the final version: a well drawn, attractively produced manuscript map. Most such maps from the 16th century are unique; rarely was a duplicate made, although some were copied by other cartographers. Many of these maps were commissioned by wealthy patrons or monarchs, or given as presentation pieces much like art. Once a map was produced, the original field sketches were discarded.

Once printed maps replaced manuscript maps, cartographers dealt directly with printers. Map reproduction involved two basic steps: the transfer of the cartographer's image to a printer's plate and the printing process itself. Both of these steps required specialists. Between the appearance of the first printed map in 1472 and the end of the 19th century, there were three ways of preparing a plate. The first printed maps were produced from smooth wood blocks, in which the image to be printed had been carved in relief by a form cutter. Since wood blocks were fragile, difficult to edit and wore out quickly, they were almost completely replaced by the mid 16th century by a new technique -- copper engraving.

Copper engraving involved the preparation of a plate by cutting (incising) the cartographic image into a flat copper sheet. In contrast to wood blocks -- where the ink adhered to a raised surface -- on a copper plate the ink filled the incisings. In both cases the cartographic image had to be cut or incised into the plate or wood surface in reverse, in order to produce a positive image. This required highly trained specialists, really artists. Many signed their plates, such as David Pelletier on Champlain's map of 1612, or the great Italian portrait engraver Giovanni Federico Pesca on the 1657 Bressani map.

Copper engraving was gradually replaced by lithography during the 19th century. This is a chemical process whereby a raised image is produced on a smooth stone surface by dissolving the unwanted areas with nitric acid. Because the woodcutter and engraver were eliminated, maps could be produced faster and more cheaply. The presses used to transfer the image to paper also varied over time. In general, wood block maps were printed on a flatbed press much like a wine press, with vertical pressure applied to a sheet of paper placed on top of the inked surface. Copper plates made the roller press necessary. This press moved the plate and slightly moistened paper between two rollers, squeezing the two together and forcing the paper into the incised image that held the ink. Both presses required cleaning and re-inking every time an image was printed. Lithographic presses were originally much like flatbed and roller presses but quickly developed their own specialized technology.


Unlike in France, where the process of collecting, compiling, storing and disseminating cartographic information was fairly systematic after 1670, mapmaking was slow to develop in England until the 1790s. In the late 16th and early 17th centuries some information was collected and published by Richard Hakluyt and Samuel Purchas, but most often, potential authors made their own arrangements with private publishers. In 1791, The Hudson's Bay Company appointed Aaron Arrowsmith to prepare maps for them and gave him access to their voluminous archives. When his first map appeared in 1795, large parts of Canada appeared on a map for the first time. Arrowsmith's maps were regularly updated and, after his death in 1823, his sons Aaron Jr. and Samuel took over the firm. With the death of Samuel in 1839, a nephew, John Arrowsmith, continued the tradition until 1873. The Arrowsmith maps are a remarkable tool for studying the growth of geographical knowledge of Canada.

In 1795, The British Admiralty finally established a Hydrographic Department similar to the French cartographic division of the Ministry of the Marine. Its first director, Alexander Dalrymple, published the first Admiralty chart in 1800. With the founding of this department, the Royal Navy ceased being dependent on private publishers for their charts, although many explorers, including naval personnel, continued to make their own publishing arrangements. Canadian map printing developed in the 1820s using the lithographic process. It expanded rapidly in Toronto, Québec and Montreal, and by the 1850s was well established with an output of large and complex maps similar in quality to those produced in Britain.

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