# Topographic Abney level

Last updated

An Abney level and clinometer , is an instrument used in surveying which consists of a fixed sighting tube, a movable spirit level that is connected to a pointing arm, and a protractor scale. An internal mirror allows the user to see the bubble in the level while sighting a distant target. It can be used as a hand-held instrument or mounted on a Jacob's staff for more precise measurement, and it is small enough to carry in a coat pocket. [1] [2]

Surveying or land surveying is the technique, profession, and science of determining the terrestrial or three-dimensional positions of points and the distances and angles between them. A land surveying professional is called a land surveyor. These points are usually on the surface of the Earth, and they are often used to establish maps and boundaries for ownership, locations, such as building corners or the surface location of subsurface features, or other purposes required by government or civil law, such as property sales.

## Contents

The Abney level is an easy to use, relatively inexpensive, and, when used correctly, an accurate surveying tool. Abney levels typically include scales graduated in measure degrees of arc, percent grade, and in topographic Abney levels, grade in feet per surveyor's chain, and chainage correction. The latter is the cosine of the angle, used to convert distances measured along the slope to horizontal distances. By using trigonometry the user of an Abney level can determine height, volume, and grade. [3]

Abney levels are made with square tubular bodies so that they may also be used to directly measure the slopes of plane surfaces by simply placing the body of the level on the surface, adjusting the level, and then reading the angle off of the scale.

## Origins

The Abney level was invented by Sir William de Wiveleslie Abney (Born 24 Jul 1843 Died 3 Dec 1920) who was an English astronomer and chemist best known for his pioneering of color photography and color vision. Abney invented this instrument under the employment of the School of Military Engineering in Chatham, England prior to late 1870. It is described by W. & L. E. Gurley as an English modification of the Locke hand level. [1]

Sir William de Wiveleslie Abney was an English astronomer, chemist, and photographer.

The Royal School of Military Engineering (RSME) Group provides a wide range of training not only in all the engineering disciplines that are fundamental to the Royal Engineers, but also Military Working Animals; their handlers and maintainers, Explosive Ordnance Disposal and Military Musicians. The scope of training delivered by the RSME Group ranges from combat engineers to Army musicians, chartered engineers to veterinary technicians and bomb disposal operators to heavy plant operators.

Elliott Brothers of London registered an "improved clinometer and spirit level combined" in December 1870 based on "the old form as originally designed by Lieutenant Abney." [4]

Elliott Brothers (London) Ltd was an early computer company of the 1950s–60s in the United Kingdom. It traced its descent from a firm of instrument makers founded by William Elliott in London around 1804. The research laboratories were originally set up in 1946 at Borehamwood and the first Elliott 152 computer appeared in 1950.

By 1871, a committee of the Royal Geographical Society recommended a long list of instruments that explorers should carry. Along with necessary tools such as a watch, compass, sextant and plenty of paper, the committee included "a pocket level (Abney's)" in a secondary list of "additional instruments, not necessary, but convenient." [5]

The Royal Geographical Society is the UK's learned society and professional body for geography, founded in 1830 for the advancement of geographical sciences. Today, it is the leading centre for geographers and geographical learning. The Society has over 16,500 members and its work reaches millions of people each year through publications, research groups and lectures.

## Usage

In 1914 and 1915, the Forestry Quarterly published a series of articles on the use of the Abney level. [6] [7] [8] These tutorial articles remain useful today, but the primary reference for usage is the 1927 Abney Level Handbook. [3]

The Abney level is typically used at the eye height of the surveyor, either hand-held or mounted on a staff at that height. To measure lines on a particular slope, the desired angle or grade is first set on the level and then the surveyor sights through the sighting tube and brings the cross-hair in line with the bubble in the level while viewing the target. This allows the surveyor to see if the target is above or below the line of sight.

To measure an unknown slope, the surveyor first sights a target along that slope and then adjusts the angle of the level until the bubble is centered on the cross-hair. Once this is done, the slope may be read from the scale.

Because the level is typically held at the surveyor's eye-height, it is common to use the face of a second surveyor of similar height as a target. If the second surveyor is not the same height, the approximate location of eye-height must be noted (i.e. chin, nose, top of head). Mounting a face-sized target at eye-height on a level staff may be more accurate. Because most Abney levels do not contain a telescope, direct reading from a level staff is only possible at short range, although it is possible to make special staffs that can be read at a distance without magnification.

## Common uses

Abney levels remain in common use in several fields:

• In topographic surveying, to place high precision surveying equipment, particularly in rough terrain. [9]
• In forestry, for tree height measurement. [10]
• In mining and mine safety inspection, to measure the grades of haulage roads. [11]
• In geology, in measurements of rock outcrops and fault scarps. [12] [13] [14]

## Related Research Articles

Indirect fire is aiming and firing a projectile without relying on a direct line of sight between the gun and its target, as in the case of direct fire. Aiming is performed by calculating azimuth and inclination, and may include correcting aim by observing the fall of shot and calculating new angles.

A theodolite is a precision optical instrument for measuring angles between designated visible points in the horizontal and vertical planes. The traditional use has been for land surveying, but they are also used extensively for building and infrastructure construction, and some specialized applications such as meteorology and rocket launching.

A spirit level, bubble level or simply a level is an instrument designed to indicate whether a surface is horizontal (level) or vertical (plumb). Different types of spirit levels may be used by carpenters, stonemasons, bricklayers, other building trades workers, surveyors, millwrights and other metalworkers, and in some photographic or videographic work.

A total station (TS) or total station theodolite (TST) is an electronic/optical instrument used for surveying and building construction. It is an electronic transit theodolite integrated with electronic distance measurement (EDM) to measure both vertical and horizontal angles and the slope distance from the instrument to a particular point, and an on-board computer to collect data and perform triangulation calculations.

An inclinometer or clinometer is an instrument used for measuring angles of slope, elevation, or depression of an object with respect to gravity's direction. It is also known as a tilt indicator, tilt sensor, tilt meter, slope alert, slope gauge, gradient meter, gradiometer, level gauge, level meter, declinometer, and pitch & roll indicator. Clinometers measure both inclines and declines using three different units of measure: degrees, percent, and topo. Astrolabes are inclinometers that were used for navigation and locating astronomical objects from ancient times to the Renaissance.

Levelling or leveling ; is a branch of surveying, the object of which is to establish or verify or measure the height of specified points relative to a datum. It is widely used in cartography to measure geodetic height, and in construction to measure height differences of construction artifacts.

A laser rangefinder is a rangefinder that uses a laser beam to determine the distance to an object. The most common form of laser rangefinder operates on the time of flight principle by sending a laser pulse in a narrow beam towards the object and measuring the time taken by the pulse to be reflected off the target and returned to the sender. Due to the high speed of light, this technique is not appropriate for high precision sub-millimeter measurements, where triangulation and other techniques are often used.

The term Jacob's staff, also known as cross-staff, a ballastella, a fore-staff, or a balestilha, is used to refer to several things. In its most basic form, a Jacob's staff is a stick or pole with length markings; most staffs are much more complicated than that, and usually contain a number of measurement and stabilization features. The two most frequent uses are:

Gun laying is the process of aiming an artillery piece, such as a gun, howitzer, or mortar, on land or at sea, against surface or air targets. It may be laying for direct fire, where the gun is aimed similarly to a rifle, or indirect fire, where firing data is calculated and applied to the sights. The term includes automated aiming using, for example, radar-derived target data and computer-controlled guns.

A level is an optical instrument used to establish or verify points in the same horizontal plane in a process known as levelling, and is used in conjunction with a levelling staff to establish the relative heights levels of objects or marks. It is widely used in surveying and construction to measure height differences and to transfer, measure, and set heights of known objects or marks.

Stadiametric rangefinding, or the stadia method is a technique of measuring distances with a telescopic instrument. The term stadia comes from a Greek unit of length Stadion which was the typical length of a sports stadium of the time. Stadiametric rangefinding is used for surveying and in the telescopic sights of firearms, artillery pieces, or tank guns, as well as some binoculars and other optics. It is still widely used in long-range military sniping, but in many professional applications it is being replaced with microwave, infrared, or laser rangefinding methods. Although much easier to use, electronic rangefinders can give away the shooter's position to a well-equipped adversary, and the need for accurate range estimation existed for much longer than electronic rangefinders small and rugged enough to be suitable for military use.

Tacheometry, is a system of rapid surveying, by which the horizontal and vertical positions of points on the earth's surface relative to one another are determined without using a chain or tape, or a separate levelling instrument. Instead of the pole formerly employed to mark a point, a staff similar to a level staff is used. This is marked with heights from the base or foot, and is graduated according to the form of tacheometer in use.

A Brunton compass, properly known as the Brunton Pocket Transit, is a precision compass made by Brunton, Inc. of Riverton, Wyoming. The instrument was patented in 1894 by a Canadian-born geologist named David W. Brunton. Unlike most modern compasses, the Brunton Pocket Transit utilizes magnetic induction damping rather than fluid to damp needle oscillation. Although Brunton, Inc. makes many other types of magnetic compasses, the Brunton Pocket Transit is a specialized instrument used widely by those needing to make accurate navigational and slope-angle measurements in the field. Users are primarily geologists, but archaeologists, environmental engineers, mining engineers and surveyors also make use of the Brunton's capabilities. The United States Army has adopted the Pocket Transit as the M2 Compass for use by crew-served artillery.

A cave survey is a map of all or part of a cave system, which may be produced to meet differing standards of accuracy depending on the cave conditions and equipment available underground. Cave surveying and cartography, i.e. the creation of an accurate, detailed map, is one of the most common technical activities undertaken within a cave and is a fundamental part of speleology. Surveys can be used to compare caves to each other by length, depth and volume, may reveal clues on speleogenesis, provide a spatial reference for other areas of scientific study and assist visitors with route-finding.

A level staff, also called levelling rod, is a graduated wooden or aluminium rod, used with a levelling instrument to determine the difference in height between points or heights of points above a vertical datum. It cannot be used without a leveling instrument.

The relascope, invented by Walter Bitterlich, is a multi-use instrument for forest inventory. It is primarily used to find the height of a tree, the basal area of a tree, and the diameter of a tree anywhere along the bole. This instrument is used mostly for applications involving variable radius sample plots in a forest survey.

A hand compass is a compact magnetic compass capable of one-hand use and fitted with a sighting device to record a precise bearing or azimuth to a given target or to determine a location. Hand or sighting compasses include instruments with simple notch-and-post alignment ("gunsights"), prismatic sights, direct or lensatic sights, and mirror/vee (reflected-image) sights. With the additional precision offered by the sighting arrangement, and depending upon construction, sighting compasses provide increased accuracy when measuring precise bearings to an objective.

Tree height is the vertical distance between the base of the tree and the tip of the highest branch on the tree, and is difficult to measure accurately. It is not the same as the length of the trunk. If a tree is leaning, the trunk length may be greater than the height of the tree. The base of the tree is where the projection of the pith (center) of the tree intersects the existing supporting surface upon which the tree is growing or where the acorn sprouted. If the tree is growing on the side of a cliff, the base of the tree is at the point where the pith would intersect the cliff side. Roots extending down from that point would not add to the height of the tree. On a slope this base point is considered as halfway between the ground level at the upper and lower sides of the tree. Tree height can be measured in a number of ways with varying degrees of accuracy.

This is a glossary of levelling terms. Levelling is a surveying method used to find relative height, one use of which is to ensure ground is level during construction, for example, when excavating to prepare for laying a foundation for a house.

## References

1. Smaller Instruments and Appliances: The Abney Level and Clinometer, A Manual of the Principal Instruments used in American Engineering and Surveying, W. & L. E. Gurley, Troy, NY, 1891; page 219.
2. George William Usill, Clinometers: The Abney Level, Practical Surveying, Crosby Lockwood and Son, London, 1889; page 33.
3. H. A. Calkins and J. B. Yule, The Abney Level Handbook, United States Forest Service, 1927.
4. Combined Clinometer and Spirit Level, The Mechanics Magazine, Dec. 30, 1870; page 476.
5. Admiral Sir George Back, Vice-Admiral Richard Collinson, and Francis Galton, Hints to Travellers (Third and Revised Edition), Proceedings of the Royal Geographical Society, Vol. XVI, No. 1 (Dec. 18, 1871).
6. William J. Paeth, Obtaining Vertical Control of Practical Value with the Abney Hand Level, Forestry Quarterly, Vol. XXII, No. 3 (Sept. 1914); page 347.
7. M. L. Erickson, The Use of the Abney Hand Level, Forestry Quarterly, Vol. XXII, No. 3 (Sept. 1914); page 370.
8. C. R. Anderson, The Abney Hand Level and the Chain on Intensive Forest Surveys, Forestry Quarterly, Vol. XIII, No. 3 (Sept. 1915); page 338.
9. Andy Nisbet, Noel Williams, Alan Brook, et al., Survey of the Basteir Tooth, The Scottish Mountaineering Club, Sept. 13, 2013; see page 1 and the top photo on page 7.
10. The Abney Level, Texas Tree Trails, Sept. 7, 2008.
11. Chapter 4: Grades, Haul Road Inspection Handbook, MSHA Handbook Number PH99-I-4, U.S. Mine Safety and Health Administration, June 1, 1999.
12. George O. Bachman and Donald A. Myers, Geology of the Bear Peak Area Dona Ana County New Mexico, Geological Survey Bulletin 1271-C, 1969; see page C3.
13. Lee Piekarsk, Relative Age Determination of Quaternary Fault Scarps along the Southern Wasatch, Fish Springs, and House Ranges, Utah, Brigham Young University Geology Studies Archived 2015-01-07 at the Wayback Machine ., Vol. 27, Part 2 (Nov. 1980); pages 123-139, particularly page 124.
14. William C. Clyde, Suyin Ting, Kathryn E. Snell, et al., New Paleomagnetic and Stable-Isotope Results from the Nanxiong Basin, China, The Journal of Geology, Vol 118 (2010); pages 131–143, particularly page 134.
• Bryn Hubbard, Neil F.(2005), Glasser Field Techniques in Glaciology and Glacial Geomorphology, John Wiley and Sons, 400pp, ISBN   0-470-84427-2.