The close of the 15th century witnessed a great revival in the art of map-making, which was materially aided by the newly perfected arts of wood and copper engraving. Further more, Purbach, Regiomontanus and others in troduced trigonometry, and attempts were made to construct maps based on systematic geo graphical triangulations. Map-making became a favorite occupation with the Germans, French and Italians, and many valuable editions of maps were produced at Strassburg, Ulm, Basle, Cologne, Paris, Lyons, Vicenza, Venice, Bologna and Rome, representing the work of numerous eminent map-makers, among which those of Joh. Ruysch, Nicolaus Donis and Jacob Angelus de Scarparia were of especial prominence and value.
During the 16th century the number of map makers increased greatly and brought forward such illustrious cartographers as Johann Werner of Nuremberg, Sebastian Cabot and Gerhard Kramer (more commonly known as Mercator). The general endeavor of the Germans during this period was directed toward the improve ment of the methods of projection originated by the Greeks, and led in the case of Mercator to the development of the .projection which hears his name, and which is even at the present time very extensively used in the construction of nautical maps. About the latter part of the century the centre of map-making effort was transferred to Holland, mainly through the in fluence of the collection of maps published by Abraham Ortelius of Antwerp, under the title (Theatrum Orbis Terrarum,) which included new engravings of the best maps from all countries. This great work passed through many editions, each successive edition being characterized b' an increased number of maps. The 12th edition contained 92 maps. The earlier editions were printed in Latin, but later, editions in German, French, Dutch, Italian and English were produced and obtained world-wide circulation.
The beginning of the 17th century inaugu rated a still further improvement in the art. The important inventions, such as the telescope, the sextant and the chronometer, provided means for the taking of more accurate observa tions relative to time, latitude and longitude, while the application of trigonometry to geod esy by Snellius and Picard's measurement of a degree of the meridian between Paris and Amiens introduced more precise methods of computation. Some of the most important pro ductions of this epoch are those of Johann Baptist Homann of Nuremberg, and the work of Nicolas Sanson, Guill de l'Isle and Jean Baptiste Bourignon d'Anville and other eminent geographers of France working under the royal patronage, and Atlas) published in England under the patronage of the Duke of Argyle.
These important works carry the art of map through a period of over 200 years and bring it to a point where instead of being treated as a matter of private business enter prise it was taken up as a governmental matter, and the original surveys, together with the maps based thereon, were executed at the cost of the state. The first step in this direction was taken by France, the object being the production of a series of maps for military purposes and as a cadastre for the land tax. For this purpose the entire country was covered with a network of triangles connecting numerous stations, the posi tions of which were astronomically determined. The maps constructed from the data thus ob tained far surpassed in the correctness of detail all those of earlier date. The example set by France has been followed by all of the first class nations of the world, and by some of lesser importance. In Europe practically the whole continent, with the exception of the Balkan States, have been surveyed and mapped at the expense of the governments of the vari ous countries. Outside of Europe, the principal large areas covered by surveys based on exact triangulations are the United States, a part of the Dominion of Canada, the whole of British India, a portion of Asiatic Russia and small portions of Australia, South Africa, the Dutch East Indies and Algeria.
all practical purposes. Such a system of lines of reference constitutes a projection by means of which any point or line on the surface of the sphere may be plotted on the map from its known co-ordinates, or from which the co ordinates of any plotted point may be ascer tained.
There are two general classes of such pro jections— the ((true° or "perspective' projec tions which depend upon the actual position of the spectator's eye, and the °developed" projec tions in which the eye is assumed at the centre of the sphere, or else occupies an arbitrary position.
Perspective Projections are of three kinds: (1) the oorthographic,)) with the eye supposed at an infinite distance, and the plane of projec tion perpendicular to the line of sight; (2) the The science and art of modern map-con struction may be considered most conveniently and usefully under three headings—theoretical projections, practical methods of construction and duplication of reproduction.