History Of Surveying Equipment – Part 2

Continuing from – Part 1

Measuring Rope – The ancient Egyptian surveyors used various measuring ropes, plumb bobs, sighting instruments and also leveling instruments. The measuring rope was stretched between stakes and rubbed with combination of beeswax and resin.

Diopter – It is well known that the Greeks developed the science of geometry and they have used its principles for precise land measurements. The first piece of surveying equipment, the diopter, was developed by them. This portable surveying instrument was used for making terrestrial and astronomical measurements. The diopter is seen and recognized as ancestor of the theodolite which is used today.

Magnetic Compass – The magnetic compass was invented by the Chinese, probably during the Han dynasty, around 221- 205 BC. This surveying tool was designed on a square slab that had markings showing the cardinal points and constellations. The needle in the center of the compass was a lodestone spoon shaped tool, which had a handle pointing always to south. Magnetic needles for showing directions arrived in the 8th century AD in China and replaced the spoon shaped needles.

Sextant – The sextant is a navigation tool which is mainly used for measuring and determining angles between different points and altitudes of celestial bodies. The sextant got its name because it has an arc of 60 degrees or 1/6 of a full circle. This device was invented by two inventors, John Hadley, an English mathematician and Thomas Godfrey, an American inventor.

Theodolite – The Jesse Ramsden theodolite is a big device that was specially designed to be used during the first Ordnance Survey of Southern Britain in 1787. This device was certainly big technological innovation in the field of geodetic surveying. Theodolites are used mainly for surveying applications. Today, the modern theodolite has a moveable telescope which is placed between two perpendicular axes, one horizontal and one vertical. The theodolites can be either transit or non transit.

Alidade – The term alidade refers to a sighting mechanism which is used for surveying or for navigation. The very first alidades were like bars with open parts on each end. Telescopic alidades were first used in Europe in the 19th century. The alidade, or also known as a turning point, is a piece of surveying equipment that is mainly used for mapping in the horizontal plane. The angles that are measured can either be horizontal or vertical.

Dumpy Level – The dumpy level was introduced in the 1830 by William Gravatt. It was a simple device which consisted of one small telescope. It also had a bubble level attached to the telescope. The dumpy level had small and fat telescope and it was considered as a standard surveying equipment until it was replaced by the transit level.

Continue Reading – Part 3