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Surveying

Dumpy Level

Introduction
A dumpy level, also known as an automatic level or builder’s level, is a tool used to determine the elevation of landmasses. Though they may appear intimidating or confusing, dumpy levels are relatively simple to use once you understand how to set them up and what types of measurements they provide.

Dumpy levels are also known as builder levels, Y levels, and so on. Willian Gravatt invented it in 1832. The dumpy level’s operation establishes the relationship between two or more points on a horizontal surface using an inbuilt telescope and a bubble level. The primary advantage of using the Dumpy level over other leveling instruments is its greater accuracy. For most Tacheometric methods, a dumpy level is known for high precision values. A dumpy level’s accuracy can be as high as 1:4000 for every 100 meters.
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Precautions in Levelling

Keywords: Levelling, precautions, errors in leveling

Since you have acquired a good understanding about leveling, let’s now move on to the last topic in this section.

Levelling has to be done with utmost care to obtain accurate and precise readings. Any error in the readings could possibly harm all the calculation and subsequent surveying processes.

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Difficulties in levelling

Keywords: Levelling, difficulties in levelling, errors in levelling

The last two topics in leveling are the difficulties and precautions to be taken for an error-free levelling process. Let’s jump into the first section, difficulties in levelling.

Some of the difficulties that are commonly encountered in levelling are:

When the staff station is more than 3metres above the line of sight
Solution: Measure the distance (d) from line of sight to the staff placed at the station accurately with a tape.
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Problem of missing entries in the field book

Keywords: Levelling examples, levelling, rise and fall method, missing entries problem

Since we have already studied about levelling, now let’s move on to a specific problem in this section. The problem of missing entries in the field book is an application level problem, often asked in question papers. An example on this type of problem is illustrated as follows:

Problem: The following level readings have been taken from a page of a level book. Some of the readings are missing. It is required to fill all the entries in the page. Fill up the missing readings and apply the arithmetic checks.
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Booking the staff reading and reduction of levels

Keywords: Levelling, reduction of levels, rise and fall methods, height of instrument

In the previous posts we have learned about the leveling, its principles and methods. Now we can move on to a practical illustration of this leveling process.

A level filed book or a level book is used for booking and reducing the levels of various points in a systematic way. There are two methods for reducing the levels namely

  • The height of the instrument method
  • The rise and fall method

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