Levelling is the branch of surveying the object of which is : 1. To find the elevations of the given points with respect to a given or assumed datum, and 2. To establish points at a given elevations or at different elevations with respect to a given or assumed datum. The operation is required in the setting out of all kind of engineering works. levelling deals with measurements in a vertical plane. MEATHODS OF LEVELLING
Three principal methods are used for determining difference in elevations, namely, barometric levelling, trigonometric levelling, and spirit levelling. LEVELLING INSTRUMENTS
The instruments commonly used in direct levelling are :
1. A level
2. A levelling staff
The purpose of a level is to provide horizontal sight. Essentially, a level consists of the following four parts : a. A telescope to provide line of sight.
b. A level tube to make the line of site horizontal.
c. A levelling head (tribrach or trivet stage) to bring the bubble its centre of run. d. A tripod to support the instrument.
An Auto Level machine is the equipment used for all surveying and engineering level applications. They are suitable for obtaining accurate levels during surveys even if the ground is not levelled. For this, an automatic level comes complete with an internal compensator mechanism which is a swinging prism. When this mechanism is set close to level, it automatically removes any remaining variation from level. This reduces the requirement to set the instrument truly level even when it is a dumpy or tilting level. It is, therefore, a self-levelling instruments designed by auto level manufacturers for accuracy, ease of operation and rugged dependability. Auto level is now the preferred instrument on building sites, construction and surveying due to ease of use and rapid setup time. They also give maximum portability. Most of the auto levels are supplied with alumnium telescopic tripod stand.
Types of Survey Auto Levels
Basically, four types of survey auto levels are available with the auto level manufacturers of which auto level is the most popular type of survey levels. * Optical level (There are two types of optical levels- dumpy level and tilted level) * Automatic or Auto level
* Electronic level
* Laser level
To know detailed features and working of these levels, read Types of Survey Levels
Features of Auto Level Instrument
With the rising popularity of auto levels for surveying and other engineering application, the auto level manufacturers have included many useful features in today's automatic levels. The popular features of any auto level include: * Most of the auto levels are provided with aluminum telescopic tripod stand. * They are rigidly constructed and ensure accuracy for years under severe conditions. * Available in various types of models.
* They are provided with durable Lithium battery that is good for many operations. * They can be set up very easily.
* Includes hard shell carrying case with dual latches, plumb bob, Allen wrench, adjusting pin, and instruction manual. * Ensures accurate levelling.
* The equipment has easy adjusting features.
* They are portable.
Functions of Auto Level Instrument
Auto level equipment have dominated the most of the market due to the useful features they provide for surveying and engineering work. Some of the important functions performed by an auto level include: * Conducting research work smoothly in extreme weather conditions. * Ensuring accuracy to the test performed.
* Making telescopic magnification possible through the apparatus.
Applications of Auto Level Instrument
Auto Level equipment are mainly used to obtain accurate levelling while surveying, engineering and other such works. Some of the applications of auto level include: * Excavation
* Optical Surveys
* Topographic Surveys