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Civil Surveying - Theodolite Surveying

Intro to Antique Survey Instruments

   Posted On :  21.08.2016 10:32 am

First, some basics about their composition and finish... most instruments were made of wood, brass, or aluminum, although you will find whole instruments or instrument parts made of iron, steel, ebony, ivory, celluloid, and plastic.


INTRO TO ANTIQUE SURVEY INSTRUMENTS

 

First, some basics about their composition and finish... most instruments were made of wood, brass, or aluminum, although you will find whole instruments or instrument parts made of iron, steel, ebony, ivory, celluloid, and plastic. It is important to remember that many surveying instruments were "needle" instruments and their magnetic needles would not seek north properly if there were local sources of interference, such as iron. The United States General Land Office issued instructions requiring brass Gunters chains to be used in close proximity to the magnetic needle. (They soon changed that requirement to steel brazed link chains; the brass chain could not stand up to the type of wear and tear a chain received.

 

In American surveying instruments, wood was common until about 1800; brass instruments were made approximately 1775 to 1975, and aluminum instruments from 1885 to the present.

 

The finish of instruments has changed. Early wooden instruments were generally unfinished and were usually made of tight grained woods which resisted water well. Early brass instruments were usually unfinished or polished and lacquered to retain the shine. In the mid-1800s American instrument makers began finishing brass instruments with dark finishes for two reasons: first, that the dark finish reduced glare and as a result reduced eyestrain, and secondly, that the dark finish helped to even out the heating of an instrument in the sunlight and as a result reduced collimation problems caused by the heating. Beware of being taken in by polished and lacquered brass instruments; prior to 1900 that may have been the original finish for the instrument, but after 1900 , bright brass finishes are usually not original finishes.

 

 

There are three kinds of surveying instruments that are rather unique to North American surveying. They are the compass, the chain and the transit. In addition, the engineer's or surveyor's level contributed very strongly to making the United States the leading industrial nation in the world by virtue of the highly efficient railroad systems it helped design in the mid 1800's. I take a great deal of satisfaction in pointing out that in this country it was the compass and chain that won the west, not the six-shooter!

 

The following is a list of antique surveying instruments and tools with a brief and basic description of how they were used.

 

ABNEY HAND LEVEL - Measures vertical angles.

 

ALIDADE - Used on a Plane Table to measure vertical and horizontal angles & distances.

 

ALTAAZIMUTH INSTRUMENT - Measures horizontal and vertical angles; for position "fixing".

 

ASTRONOMIC TRANSITS - Measures vertical angles of heavenly bodies; for determining geographic position.

 

BAROMETER, ANEROID - Measures elevations; used to determine vertical distance.

 

BASE-LINE BAR - Measures horizontal distances in triangulation and trilateration surveys.

 

BOX SEXTANT - Measures vertical angles to heavenly bodies.

 

CHRONOGRAPH - Measures time.

 

CHRONOMETER - Measures time.

 

CIRCUMFERENTER - Measures horizontal directions and angles.

 

CLINOMETER - Measures vertical angles.

 

COLLIMATOR - For adjusting and calibrating instruments.

 

COMPASSES - Determines magnetic directions; there are many kinds, including plane, vernier, solar, telescopic, box, trough, wet, dry, mariners, prismatic, pocket, etc.

 

CROSS, SURVEYORS - For laying out 90 and 45 degree angles.

 

CURRENT METER - Measures rate of water flow in streams and rivers.

 

DIAL, MINER'S - A theodolite adapted for underground surveying; measures directions as well as horizontal and vertical angles.

 

GONIOMETER - Measures horizontal and vertical angles.

 

GRADIOMETER - Also known as Gradiometer level, it measures slight inclines and level lines-of-sight.

 

HELIOGRAPH - Signalling device used in triangulation surveys.

 

HELIOSTAT - Also known as a heliotrope, it was used to make survey points visible at long distances, particularly in triangulation surveys.

 

HORIZON, ARTIFICIAL - Assists in establishing a level line of sight, or "horizon".

 

HYPSOMETER - Used to estimate elevations in mountainous areas by measuring the boiling points of liquids. This name was also given to an instrument which determined the heights of trees.

 

INCLINOMETER - Measures slopes and/or vertical angles.

 

LEVEL - Measures vertical distances (elevations). There are many kinds, including Cooke's, Cushing's, Gravatt. dumpy, hand or pocket, wye, architect's, builder's, combination, water, engineer's, etc.

 

LEVELLING ROD - A tool used in conjunction with a levelling instrument.

 

LEVELLING STAVES - Used in measuring vertical distances.

 

MINER'S COMPASS - Determines magnetic direction; also locates ore.

 

MINER'S PLUMMET - A "lighted" plumb bob, used in underground surveying.

 

MINING SURVEY LAMP - Used in underground surveying for vertical and horizontal alignment.

 

OCTANT - For measuring the angular relationship between two objects.

 

PEDOMETER - Measures paces for estimating distances.

 

PERAMBULATOR - A wheel for measuring horizontal distances.

 

PHOTO-THEODOLITE - Determines horizontal and vertical positions through the use of "controlled" photographs.

 

PLANE TABLE - A survey drafting board for map-making with an alidade.

 

PLUMB BOB - For alignment; hundreds of varieties and sizes.

 

PLUMMETS - Same as plumb bob.

 

QUADRANT - For measuring the angular relationship between two objects.

 

RANGE POLES - For vertical alignment and extending straight lines.

 

SEMICIRCUMFERENTER - Measures magnetic directions and horizontal angles.

 

SEXTANTS - Measures vertical angles; there are many kinds, including box, continuous arc, sounding, surveying, etc.

 

SIGNAL MIRRORS - For communicating over long distances; used in triangulation surveys.

 

STADIA BOARDS - For measuring distances; also known as stadia rods.

 

STADIMETER or STADIOMETER - For measuring distances.

 

TACHEOMETER - A form of theodolite that measures horizontal and vertical angles, as well as distances.

 

TAPES - For measuring distances; made of many materials, including steel, invar, linen, etc. Also made in many styles, varieties, lengths, and increments.

 

THEODOLITE - Measures horizontal and vertical angles. Its name is one of the most misused in surveying instrument nomenclature, and is used on instruments that not only measure angles, but also directions and distances. There are many kinds, including transit, direction, optical, solar, astronomic, etc.

 

TRANSIT - For measuring straight lines. Like the theodolite, the transit's name is often misused in defining surveying instruments. Most transits were made to measure horizontal and vertical angles and magnetic and true directions. There are many kinds, including astronomic, solar, optical, vernier, compass, etc.

 

WAYWISER - A wheel for measuring distances


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