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While the works of almost all earlier geographers have been lost, many of them are partially known through quotations found in Strabo (64/63 BC – ca. AD 24). Strabo's seventeen volume work of geography is almost completely extant, and is one of the most important sources of information on classical geography. Strabo accepted the narrow band of habitation theory, and rejected the accounts of Hanno and Pytheas as fables. None of Strabo's maps survive, but his detailed descriptions give a clear picture of the status of geographical knowledge of the time. Pliny the Elder's (AD 23 – 79) Natural History also has sections on geography. A century after Strabo Ptolemy (AD 90 – 168) launched a similar undertaking. By this time the Roman Empire had expanded through much of Europe, and previously unknown areas such as the British Isles had been explored. The Silk Road was also in operation, and for the first time knowledge of the far east began to be known. Ptolemy's Geographia opens with a theoretical discussion about the nature and techniques of geographical inquiry, and then moves to detailed descriptions of much the known world. Ptolemy lists a huge number of cities, tribes, and sites and places them in the world. It is uncertain what Ptolemy's names correspond to in the modern world, and a vast amount of scholarship has gone into trying to link Ptolemaic descriptions to known locations. It was the Romans who made far more extensive practical use of geography and maps. The Roman transportation system, consisting of 55,000 miles of roads, could not have been designed without the use of geographical systems of measurement and triangulation. The cursus publicus, a department of the Roman government devoted to transportation, employed full-time grommatici (surveyors). The surveyors’ job was to gather topographical information and then to determine the straightest possible route where a road might be built. Instruments and principles used included sun dials for determining direction, theodolites for measuring horizontal angles,[12] and triangulation without which the creation of perfectly straight stretches, some as long as 35 miles, would have been impossible. During the Greco-Roman era, those who performed geographical work could be divided into four categories:[13] Land surveyors determined the exact dimensions of a particular area such as a field, dividing the land into plots for distribution, or laying out the streets in a town. Cartographical surveyors made maps, involving finding latitudes, longitudes and elevations. Military surveyors were called upon to determine such information as the width of a river an army would need to cross. Engineering surveyors investigated terrain in order to prepare the way for roads, canals, aqueducts, tunnels and mines. Around AD 400 a scroll map called the Peutinger Table was made of the known world, featuring the Roman road network. Besides the Roman Empire which at that time spanned from Britain to the Middle East and Africa, the map includes India, Sri Lanka and China. Cities are demarcated using hundreds of symbols. It measures 1.12 ft high and 22.15 ft long. The tools and principles of geography used by the Romans would be closely followed with little practical improvement for the next 700 years.[14] |
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