Each revolution of the wheel measures a specific distance, such as a yard, meter or half-rod. Thus counting revolutions with a mechanical device attached to the wheel measures the distance directly.
Surveyor's wheels will provide a measure of good accuracy on a smooth surface, such as pavement. On rough terrain, wheel slippage and bouncing can reduce the accuracy. Soft sandy or muddy soil can also affect the rolling of the wheel. As well, obstacles in the way of the path may have to be accounted for separately. Good surveyors will keep track of any circumstance on the path that can influence the accuracy of the distance measured and either measure that portion with an alternative, such as a surveyor's tape or measuring tape, or make a reasonable estimate of the correction to apply.
Surveyor's wheels are used primarily for lower accuracy surveys. They are often used by road maintenance or underground utility workers and by farmers for fast measures over distances too inconvenient to measure with a surveyor's tape.
The surveyor's wheel measures the distance along a surface, whereas in normal land surveying, distances between points are usually measured horizontally with vertical measurements indicated in differences in elevation. Thus conventionally surveyed distances will be less than those measured by a surveyor's wheel.
A tape measure or measuring tape is a flexible form of ruler. It consists of a ribbon of cloth, plastic, fiber glass, or metal strip with linear-measurement markings. It is a common measuring tool. Its flexibility allows for a measure of great length to be easily carried in pocket or toolkit and permits one to measure around curves or corners. Today it is ubiquitous, even appearing in miniature form as a keychain fob, Fiberglass measuring tape, Tailor’s tape, BMI tape, oil measuring tape, Color scale tape for express delivery, Diameter measuring tape ,Size tape for fishing, Fiberglass ribbon or novelty item. Surveyors use tape measures in lengths of over 100 m (300+ ft).
SPIRIT LEVEL & LEVEL VIAL (BUBBLE)
A spirit level or bubble 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, stone masons, bricklayers, other building trade's workers, surveyors, millwrights and other metalworkers, and in some photographic or video graphic work.
Original spirit levels had two banana-shaped curved glass vials at each viewing point and were much more complicated to use. In the 1920s, Henry Ziemann, the founder of Empire Level, invented the modern level with a single vial. These vials, common on most ordinary levels today, feature a slightly curved glass tube which is incompletely filled with a liquid, usually a colored spirit or alcohol, leaving a bubble in the tube. At slight inclinations the bubble will travel away from the center position, which is usually marked in some manner.
Alcohols such as ethanol are often used rather than water for a variety of reasons. Alcohols generally have very low viscosity and surface tension, which allows the bubble to travel the tube quickly and settle accurately with minimal interference with the glass surface. Alcohols also have a much wider liquid temperature range, and won't break the vial as water could due to ice expansion. A colorant such as fluoresce in, typically yellow or green, may be added to increase the visibility of the bubble.
Some spirit levels are capable of indicating the level of a surface between horizontal and vertical to the nearest degree. The crudest form of the spirit level is the bull's eye level: a circular flat-bottomed device with the liquid under a slightly convex glass face which indicates the center clearly. It serves to level a surface in two perpendicular directions, while the tubular level only does so in the direction of the tube. The most sophisticated spirit levels are guaranteed accurate to five-ten-thousandth of an inch (.0005) per inch and are much easier to read because of their green/yellow color. Where a spirit level must also be usable upside- down, the banana-shaped tube is replaced by a barrel-shaped tube. The upper internal surface of the tube is thus always of the appropriate shape.