In siting early settlements across the world mankind knew and understood the character of land, land cover and water surfaces. However, built environments have had an impact on local climates, with such intervention becoming greater with increased urbanisation (Morcos-Asaad, 1978). Urban units that mankind has developed which substitute for the pre-existing landscape of a location, thus changing both physical and chemical properties of the environment, have been discussed at length by a range of authors (e.g. Chandler, 1978).