Theodolite. Production of CAD drawings. Job advertisement. Applicant 1. . Beng. Graduated this year. . Applicant 2. Beng. Graduated in 2010. . Unit 4 construction Loadalls

THEODOLITE

A theodolite is an instrument for measuring both horizontal and vertical angles. A modern theodolite consists of a movable telescope mounted within two perpendicular axes – the horizontal and the vertical axes. When the telescope is pointed at a desired object, the angle of each of these axes can be measured with great precision.

Both axes of a theodolite are equipped with graduated circles that can be read out through magnifying lenses. The horizontal and vertical axes of a theodolite must be perpendicular. The condition where they deviate from perpendicularity and the amount by which they do is referred to as a horizontal axis error. The optical axis of the telescope, called the sight axis and defined by the optical center of the objective and the center of the crosshairs in its focal plane, must similarly be perpendicular to the horizontal axis. Any deviation from perpendicularity is the collimation error. A horizontal axis error, a collimation error, and the index error are regularly determined by calibration and are removed by mechanical adjustment at the factory in case they grow large.

A theodolite is mounted on its tripod head by means of a forced centering plate containing four thumbscrews, or in some modern theodolites, three, for rapid leveling. Before its use, a theodolite must be placed precisely and vertically over the point to be measured – centering- and its vertical axis aligned with local gravity – leveling.

The level instrument is an optical instrument used in surveying and building to transfer, measure or set horizontal levels. It is set up on a tripod and, depending on the type, either roughly or accurately set to a leveled condition using leveling screws. The operator looks through the eyepiece of the telescope while an assistant holds a tape measure or graduated staff vertical at the point under measurement.

An automatic level, self-leveling level or builder’s auto level includes an internal compensator mechanism (a swinging prism) that, when set close to level, automatically removes any remaining variation from level. This reduces the need to set the instrument truly level, as with a dumpy or tilting level. Self- leveling instruments are the preferred instrument on building sites, construction and surveying due to ease of use and rapid setup time.

A digital electronic level is also set level on a tripod and reads a bar-coded staff using electronic laser methods. The height of the staff where the level beam crosses the staff is shown on a digital display. This type of level removes interpolation of graduation by a person, thus removing a source of error and increasing accuracy.

 

Exercise 6. Make up a summary text about a theodolite.The following expressions will help you:

1. The text under the title “  ” tells us about….

Текст под        заголовком рассказывает нам о…

«    »

2. At the beginning of the text the

В начале текста автор

author underlines

подчеркивает

points out

указывает

gives definition

дает определение

characterizes

характеризует

says that

говорит, что

tells us about

информирует

informs

enumerates

перечисляет

3. Then the author passes on to…

Затем автор переходит к…

4. After that the author goes on to say about…

После этого автор         продолжает говорить о…

5. Next the author…

Затем автор…

6. In conclusion…

В заключении…

7. The author draws the conclusion that…

Автор делает вывод, что…

8. The text ends with…

Текст заканчивается…

Exercise 7.Read the text about CAD:

PRODUCTION OF CAD DRAWINGS

The development of information and communication technologies (ICT) over the past decade has revolutionized the process of building design and construction. Now computers have greater capacity, work faster, and by means of the world wide web (www) can communicate a vast amount of information securely to all interested parties in any one construction project.

The development of CAD software for personal desktop computers was the impetus for almost universal application in all areas of construction. Initially, with 2D in the 1970s, it was typically limited to producing drawings similar to hand-drafted drawings. Advances in solid modeling involving wire-frames and surface area treatments in the 1980s allowed more versatile applications of computers in design activities. Autodesk ^TM was founded in 1982 which led to the 2D system AutoCAD^TM. Further software developments in the early 1990s led to solid 3D modeling linked to database features. These could capture information about material properties and product specifications of the drawn objects, and not just treat them as a series of lines. Currently, there are many CAD software products on the market, the most popular ones being Autodesk’s AutoCAD, with its derivative programs based on its DWG file format system, Bentley’s Microstation^TM suite of programs and Graphisoft’sArchCAD^TM software system. All of them offer capabilities for managing building data to provide secure, clear and timely management of design and construction documents known as Building Information Modeling (BIM) systems.

Today, CAD programs have become highly visual with intuitive interfaces which help make the software easier to use. The keyboard and mouse are still the main input devices (although light pens and digitizers are also used in some design offices) but with less focus on dialogue or instruction boxes and more emphasis on designing directly in the virtual model space.

 

 

Exercise 8. Answer the questions:

1. How are modern computers different from the old ones?

2. What were the capabilities of 2D modeling in 1970s?

3. What are the capabilities of 3D modeling?

4. What is BIM?

5. What is the difference between CAD and CADD?

Job advertisement

- Educated to degree level, candidates should have at least two years’ relevant experience.

- We need a highly-motivated individual with good understanding and experience of CAD, CADD and BIM.

- You should be able to communicate a vast amount of information securely to all interested parties in any one construction project.

- The successful candidate must work well under pressure and as a team member.

Applicant 1.

BEng. Graduated this year.

- Knowledge of a variety of operating systems

- Experience in using CAD

- Familiar with a wide variety of software packages

- Highly motivated

 

Applicant 2

BEng. Graduated in 2010.

- Keen to get experience in using CAD and CADD

- Trained in using BIM systems

- Good communicator, experienced in dealing with the public and working as part of a team

- Highly motivated

 

Which of these candidates do you think is the best applicant?