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Monday, 8 January 2018

Total station and Auto level

From architecture drawing we got four reference coordinates on our different corner of plot. With the help of these coordinates we plot different reference coordinates with the help of total station. With the help of these coordinate we plot footing and columns
                                                        Fig: operating of total station

Working principle of total station
Total station is a surveying equipment combination of Electromagnetic Distance Measuring Instrument and electronic theodolite. It is also integrated with microprocessor, electronic data collector and storage system. The instrument can be used to measure horizontal and vertical angles as well as sloping distance of object to the instrument. The total station instrument is mounted on a tripod and is leveled by operating leveling screws. Within a small range instrument is capable of adjusting itself to the level position. Then vertical and horizontal reference directions are indexed using onboard keys. It is possible to set required units for distance, temperature and pressure (FPS or SI). Surveyor can select measurement mode like fine, coarse, single or repeated.
When target is sighted, horizontal and vertical angles as well as sloping distances are measured and by pressing appropriate keys they are recorded along with point number. Heights of instrument and targets can be keyed in after measuring them with tapes. Then processor computes various information about the point and displays on screen.
This information is also stored in the electronic notebook. At the end of the day or whenever electronic note book is full, the information stored is downloaded to computers.
The point data downloaded to the computer can be used for further processing. There are software like auto civil and auto plotter clubbed with AutoCad which can be used for plotting contours at any specified interval and for plotting cross-section along any specified line.

 2. Auto level 
With the help of auto level we mark different vertical level of structure and uniform level of slab. In auto level we mark different RL of different component of structure. The RL of ground level is 299 for our easy calculation we consider this as a zero. From these we mark different RL of structure downward side we mark negative and upward side positive.

                                                       Fig: operating of autolevel
Working principle of auto level

The term dumpy level endures despite the evolution in design. A dumpy level is an older-style instrument that requires skill to set accurately. The instrument requires to be set level (see spirit level) in each quadrant to ensure it is accurate through a full 360° traverse. Some dumpy levels will have a bubble level intrinsic to their design which ensures an accurate level. A variation on the dumpy and one that was often used by surveyors, where greater accuracy and error checking was required, is a tilting level. This instrument allows the telescope to be effectively flipped through 180°, without rotating the head. The telescope is hinged to one side of the instrument's axis; flipping it involves lifting to the other side of the central axis (thereby inverting the telescope). This action effectively cancels out any errors introduced by poor setup procedure or errors in the instrument's adjustment. As an example, the identical effect can be had with a standard builder's level by rotating it through 180° and comparing the difference between spirit level bubble positions. An automatic level uses a swinging prism to compensate for small inclination deviations. 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. 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 during 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. During night time, the dumpy level is used in conjunction with an auto cross laser for accurate scale readings.

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