leveling
chapter seven
Leveling Instruments
Many types of instruments have been used for leveling purposes. The instruments have ranged from water troughs, hoses, four-foot levels, and string-line level bubbles to instruments such as the dumpy level, automatic level, and laser. The field engineer should realize how each of these can be used to determine elevations for construction.
Instruments with Bubbles
Level bubble instruments include the builder's transit level, the transit, and the dumpy level. Each of these instruments contains a level vial with a bubble that must be cen-tered to be used for leveling. Each instrument consists of three main components: all contain a four-screw leveling head, all contain a level vial attached to the telescope, and all contain a telescope for magnification of the objective.
The Builder's Level. The builder's level is one of the most inexpensive instruments used by field engineers. It is a versatile instrument. In addition to being able to perform leveling operations, it can be used to turn angles, and the scope can be tilted for sighting. Many residential builders use this instrument be-cause it serves their purpose of laying out a building very well.
The Transit. Although the primary functions of the transit are angle measurement and layout, it can also be used for leveling because there is a bubble on the telescope. In fact, many con-struction companies who don't have both an angle-measuring instrument and a dumpy or automatic level, will do all of their leveling work with a transit. Some people prefer to use the transit for leveling because they are comfortable with its operation.
The field engineer should be aware that the transit is versatile and is used on the jobsite in an infinite number of leveling and angle-turning applications.
The Dumpy Level. The dumpy level has been the workhorse of leveling instruments for more than 150 years. It has been used extensively for many of the great railroad, canal, bridge, tunnel, building, and harbor projects for the last century and a half. It has been a mainstay of the industry in constructing projects that are level. Even with advancements in other leveling instruments such as the automatic level and the laser, the dumpy is still the instrument of choice by a number of persons in construction.
