SURVEYING: THEN & NOW

EgyptiansPlumb Bob

Groma

Merchet

A-Level

Water Level

GreeksDioptra:

The dioptra was a level that rested on the ground, and was finely adjusted by tilting and rotating the top part by means of precision screws, it could assess the angle of a stretch of aqueduct by looking through pivoting sights, very similar to today’s survey levels.

Chinese:Magnetic Compass:

Invented by the Han Dynasty (202BC –220AD). Original compasses were made of lodestone fashioned into the shape of a spoon, which rested on a square, bronze plate. The handle of the “spoon” always pointed south.

Colonial Era Surveying

Gunter’s Chain:• Invented in 1620 by English clergyman &

mathematician Edmund Gunter.• 66ft in length, containing 100 links, with rings for every

10 links.• The Gunter’s Chain reconciled two incompatible

systems: the English land measurement, based on the number 4, and decimal system based on the number 10.• An acre measured 10 square chains (or 100,000

square links) in Gunter’s system, therefore, land measurements taken in links, could then be converted to acres by dividing the results by 100,000.

• Measurements:• 1 mile = 80 chains• 1 furlong = 10 chains• 1 rod = 1/4 chain• 1 acre = 10 square chains

Replaced by the 100ft steel tape.

Look in the slide notes below for topics to consider talking about

Surveyor’s compassInvented circa 1610.The surveyor’s compass consists of a circular brass box containing a magnetic needle which swings freely over a brass circle which is divided into 360 degrees. The horizontal angle is measured using a pair of sights located on north – south axis of the compass. They are usually mounted over a tripod and leveled using a ball and socket mechanism. Became obsolete with the invention of the theodolite in the 1780s.

Solar Compass:Invented in 1836 by William Austin BurtA solar compass used the location of the sun with astronomical tables to enable surveyors to run more accurate lines, as it was not susceptible to inaccurate reading due to iron bearing minerals.

TheodoliteA precision instrument for measuring angles between visible points in the horizontal and vertical planes. It consists of a telescope mounted to graduated Vernier.

Originally invented in 1576 by German Joshua Habermel, it did not become popular until 1787, with the introduction of Jesse Ramsden’s great theodolite.Remained in use, in various forms, until 1971 with the introduction of the Total Station

Total Station:The total station was introduced in 1971 and for the first time distance and angle measurements could be recorded by one instrument. The total station is a transit integrated with an EDM, electronic distance meter, which can read slope distances from the instrument to a particular point of land. This combination gives the surveyor the capability of retrieving data related to the coordinates of the reflector in the device.

Global Positioning System (GPS):The GPS project was launched by the U.S. Department of Defense in 1973 for use by the United States military and became fully operational in 1995. It was allowed for civilian use in the 1980s.

The GPS concept is based on time and the known position of GPS specialized satellites. The satellites carry very stable atomic clocks that are synchronized with one another and with the ground clocks. Any drift from true time maintained on the ground is corrected daily. In the same manner, the satellite locations are known with great precision. GPS receivers have clocks as well, but they are less stable and less precise. At a minimum, four satellites must be in view of the receiver for it to compute four unknown quantities (three position coordinates and clock deviation from satellite time).

UAVs:Unmanned Aerial Photogrammetric Survey is the use of Unmanned Aerial Vehicles (UAVs) to take photos for use in photogrammetry. Instruments manufactured for UAVs could be mounted on unmanned flying platforms of various sizes and types. These machines are suitable for the full geodetic survey of a study site by creating a point cloud of measurements of nearly homogenous quality and accuracy. These detailed point clouds could be used in line with orthophotos etc. to obtain a complex data system representing the study site.

Light Detection & Ranging (LiDAR):

LiDAR is a remote sensing method that uses light in the form of a pulsed laser to measure variable distances to the Earth. These light pulses—combined with other data recorded by the airborne system— generate precise, three-dimensional information about the shape of the Earth and its surface characteristics.

LiDAR originated in the 1960s, but did not become popular with the surveying industry until 1998, when Cyra Technologies (later Leica Geosystems) invents the Cyrax 2400, the first tripod mounted commercial 3D scanner.

Questions?