Compass surveying is a type of surveying in which the directions of surveying lines are determined with a magnetic compass, and the length of the surveying lines are measured with a tape or chain or laser range finder. The compass is generally used to run a traverse line.
Survey Compass Pictured Courtesy of Compass Museum
What is a Survey Compass?
A Survey Compass, otherwise known as Circumferentor, is an instrument used in surveying to measure horizontal angles. It was superseded by the theodolite in the early 19th century. A circumferentor consists of a circular brass box containing a magnetic needle, which moves freely over a brass circle, or compass divided into 360 degrees. The needle is protected by a glass covering. A pair of sights is located on the North-South axis of the compass. Circumferentors were typically mounted on tripods and rotated on ball-and-socket joints. Circumferentors were made throughout Europe, including in England, France, Italy, and Holland. By the early 19th century, Europeans preferred theodolites to circumferentors. However, the circumferentor remained in common use in mines and in wooded or uncleared areas, such as in America.
Survey Compass (Compass Museum)
No maker indicated. Maybe Austrian (discovered in Vienna). Early 20th c. Probably used together with a special device like tripod. The double graduation (quadrants on disc and casing) is an evidence of it's use for survey works.
What is the Difference Between a Surveyor Compass and a Prismatic Compass?
|Prismatic compass||Surveyor compass|
|In this compass the reading are taken with the help of prism.||There is no prism on it. Reading are taken with naked eyes|
|With the help of prismatic compass whole circle bearing (W.C.B) can be measured||With the help of surveyor compass reduced bearing can be measured.|
|Graduation in prismatic compass are marked from 0to 360|
|In a prismatic compass a mirror is provided with the sight vane.||In a surveyor compass no mirror is attached to the objective vane.|
|Sighting the object as well as reading the graduated circle can simultaneously be done without changing the position of the eye.||Sighting the object as well as reading the graduated circle cannot be done simultaneously without changing the position of eye.|
Surveyor Compass History Tidbit
As most of you know, America's First President, George Washington, was a land surveyor. George Washington (1732-1799), the 1st president of the U.S., worked about 3 y. as a surveyor when he was 16-19. He maybe laid down the system of plats for the new territories (see LEUPOLD). He was interested in surveying during his whole life and utilized instruments made by RITTENHOUSE (click on link to see the picture of an engraved compass).