ELEMENTARY SURVEYING LL W/MASTERING ENGR
ELEMENTARY SURVEYING LL W/MASTERING ENGR
15th Edition
ISBN: 9780134777481
Author: GHILANI
Publisher: PEARSON
bartleby

Concept explainers

Question
Book Icon
Chapter 5, Problem 5.1P
To determine

Left thumb rule in levelling.

Expert Solution & Answer
Check Mark

Explanation of Solution

Left thumb rule is applicable in leveling for the measurement of vertical angles. In order to use the instruments effectively we must follow some of the basic principles.

Most of the latest instruments use three screw leveling head for initial rough leveling. In leveling a three-screw head, the telescope is rotated until it is over two screws that is, horizontal to the two screws, and then by using the thumb and the first finger of each hand in order to adjust the opposite screws simultaneously fixing the bubble approximately at the center (if the left thumb is turned to the left as moving right thumb to right it will turn the bubble towards left, similarly moving left thumb to right and right thumb to left will make the bubble to move towards right). The whole procedure is repeated with the telescope at 90oso that it is over the third remaining screw just opposite the other two. Now, a lot of time gets wasted while adjusting the bubble with the first attempt.A simple rule that assists in centering bubble, as a bubble follows the left thumb rule when turning the screws gets centered by turning the screws one after the other. Furthermore, the inward and outward movement of the foot screws will easily center the instrument and telescope need not to be rotated throughout the process.

Want to see more full solutions like this?

Subscribe now to access step-by-step solutions to millions of textbook problems written by subject matter experts!
Knowledge Booster
Background pattern image
Civil Engineering
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, civil-engineering and related others by exploring similar questions and additional content below.
Recommended textbooks for you
Text book image
Structural Analysis
Civil Engineering
ISBN:9781337630931
Author:KASSIMALI, Aslam.
Publisher:Cengage,
Text book image
Structural Analysis (10th Edition)
Civil Engineering
ISBN:9780134610672
Author:Russell C. Hibbeler
Publisher:PEARSON
Text book image
Principles of Foundation Engineering (MindTap Cou...
Civil Engineering
ISBN:9781337705028
Author:Braja M. Das, Nagaratnam Sivakugan
Publisher:Cengage Learning
Text book image
Fundamentals of Structural Analysis
Civil Engineering
ISBN:9780073398006
Author:Kenneth M. Leet Emeritus, Chia-Ming Uang, Joel Lanning
Publisher:McGraw-Hill Education
Text book image
Sustainable Energy
Civil Engineering
ISBN:9781337551663
Author:DUNLAP, Richard A.
Publisher:Cengage,
Text book image
Traffic and Highway Engineering
Civil Engineering
ISBN:9781305156241
Author:Garber, Nicholas J.
Publisher:Cengage Learning