Instruments to measure distance and the slope of the land helped to develop the ancient art and profession of land surveying. It is widely believed that the Egyptians were the first to invent such instruments, although one of the most influential tools, the 'groma', is said to have come from Mesopotamia. This tool was simple in appearance: a two-metre staff supported a crossed bracket, with a plumb bob hanging from each of the four cross points. It was used to assess lines and angles, and was imported by the Greeks from Mesopotamia and then introduced to the Romans by the Etruscans.
