Science & Technology in Action

Context 
Maps are of fundamental importance in planning the construction of buildings, roads and other infrastructural developments. Maps not only indicate the scale of individual constructions but also their relationship to existing structures and the local environment. In fact, planning applications are of little value without appropriate maps. 

In recent decades unusually severe weather events have been attributed to increases in the amount of various greenhouse gases in the atmosphere, particularly carbon dioxide, methane and nitrous oxide. The resultant flooding and storm surges have highlighted the need for more careful planning and risk assessment which take account of changing conditions. 

Development of maps 
A map shows how objects in the environment are related spatially. It is a graphical representation but is generally not what would normally be called a picture. It is a kind of model of the world or of a part of it in which standard symbols are used to represent items such as mountains, towns, roads, rivers etc. 

Maps have been in use for at least 4000 years, and possibly 8000 years. The early maps were based on incomplete and inaccurate information and often included fictitious or mythical details. 

By around 500 BC Greek cartographers were using more mathematical methods; the word ‘geometry’ in fact refers to measurement of the land (geo ‘land’ or ‘earth’; metron ‘measurement’). 

Eratosthenes (275–195 BC) noted that there was a 7.2 degree difference (i.e. one 50^th of a circle) in the angle of the Sun at Alexandria and at Syene (Aswan) about 800 km to the south. From that he calculated the size of the Earth to better than 99% accuracy. In his books (On the Measurement of the Earth and Geographica) he introduced the use of meridians (lines of longitude, from pole to pole) which indicate the angular distance east or west, and ‘parallels’ (lines of latitude) showing the angular distance north or south of the equator. 

Claudius Ptolemy (90–168 AD) produced a map of the known (Greco- Roman) world in eight volumes (Geographia) complete with an index of place names and their coordinates. Such books included not only maps but also descriptions of different places, peoples and customs and were of great value to travellers, explorers, traders and rulers. Kings and emperors needed them in planning communication, administration, taxes, security and indeed further expansion and so they typically commissioned teams of cartographers to produce or update maps of their realm and beyond. 

The construction of bridges and elevated aqueducts in Roman times required very precise surveying. Many of these structures are still standing today, more than two thousand years later.