introduction

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In some types of construction, such as high rise buildings, the dumpy level must be used. Vibrations in buildings occur as tower cranes and personnel hoists cause the compensator and line of sight of some automatic levels to be constantly moving making it practically impossible to take a reading on a rod. The line of sight of the dumpy level, however, basically holds steady in a similar situation. Thus, the dumpy level is the level of choice by many on high-rise construction projects. On any type of project where there is going to be a great deal of vibration, such as pile driving, heavy equipment usage, etc., the dumpy may be the best choice for a leveling instrument.

Many carpenters prefer to use a dumpy level rather than an automatic level because they can relate better to the bubble on the dumpy as opposed to the "magic" of the compensator on the automatic. In the dumpy, they can see the bubble and have confidence in the horizontal line of sight when it is centered.

Hand Levels

A simple tool, the hand level, also called a sight level, is an extremely useful tool in leveling. It consists of a hollow tube with a simple spirit level that enables the user to quickly determine a horizontal line. It can be used to roughly determine elevations for cut or fill stakes, to set slope stakes, check height differences within a few tenths, keep a chain level, or for any number of situations where an elevation doesn’t need to be exact. Just as with a plumb bob, it should be on the tool belt of anyone who is performing surveying. In differential leveling, it is used to determine where to set a leveling instrument in relation to the rod. With the hand level, an approximate line of sight is obtained, and a quick decision on where to set the instrument is made. This is described further in the standard practices Section of this Chapter.

Automatic Levels

Automatic levels were developed just after the end of WWII, and are now the predominate optical-leveling instrument. Although manufacturers use different designs of compensators, these levels essentially do the same thing—create a horizontal line of sight. An experienced operator can set up an automatic level in less than 10 seconds, as compared with the setup of several minutes with bubble-based instruments.

Some compensators have prisms suspended with wires, and others have magnetic dampeners. The illustration to the right shows how a wire suspension compensator allows the prism to swing freely while maintaining a horizontal line of sight. Note that the instrument must be manually leveled by centering a bulls-eye bubble for the compensator to work.