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Electromagnetic waves are typically described by any of the physical properties like frequency (D), wavelength (A) or photo energy (E). Frequencies ranges from 2.4 x 10 Hz to 1 Hz. Whenever electromagnetic waves exist in a medium with matter then wave length (A) is decreased. Generally electromagnetic radiation is classified into radio wave, microwave, infrared and visible region. The behavior of EM radiation depends on its wavelength. Spectroscopy can detect a much wider region of the EM spectrum than the visible range of 400 mm to 700 mm. Electronic distance measuring tool is a surveying tool for measuring distance electronically among factors via electromagnetic waves. Electronic distance dimension (EDM) is a way of figuring out the period among factors, the usage of section changes, that arise as electromagnetic electricity waves travels from one give up of the road to the opposite give up. As a background, there are 3 strategies of measuring distance among factors: DDM or Direct distance dimension - This is specifically accomplished with the aid of using chaining or taping. ODM or Optical distance dimension - This dimension is carried out with the aid of using tacheometry, horizontal subtense approach or telemetric approach. These are executed with the assist of optical wedge attachments. EDM or Electromagnetic distance dimension - The approach of direct distance dimension can't be applied in tough terrains. When massive quantity of inconsistency withinside the terrain or massive obstructions exist, this approach is avoided. As an opportunity to this optical distance dimension approach become developed. Still it received a downside of restrained variety of dimension. It is restrained to fifteen to 150m with an accuracy of one in one thousand to one in 10000. Above all we've EDM with an accuracy of one in 105, having a distance variety of 100km. Electronic distance dimension in preferred is a time period used as a way for distance dimension with the aid of using digital means. In this approach units are used to degree distance that rely upon propagation, mirrored image and reception of electromagnetic waves like radio, seen mild or infrared waves. Sun mild or artificially generated electromagnetic wave includes waves of various lengths. Mark the factor at which the theodolite could be installation with a surveyor’s nail or a stake. This factor is the premise for measuring angles and distances. Set up the tripod. Make positive the peak of the tripod permits the tool (the theodolite) to be eye-stage. The focused hollow of the mounting plate need to be over the nail or stake. Drive the tripod legs into the floor the use of the brackets on the perimeters of every leg. Mount the theodolite with the aid of using setting it atop the tripod, and screw it in region with the mounting knob. Measure the peak among the floor and the tool. This could be used a connection with different stations. Level the theodolite with the aid of using adjusting the tripod legs and the use of the bulls-eye stage. You could make mild tunings with the leveling knobs to get it simply right. Adjust the small sight (the vertical plummet) observed on the lowest of the theodolite. The vertical plummet permits you to do make certain the tool stays over the nail or stake. Adjust the plummet the use of the knobs on the lowest. Aim the crosshairs withinside the foremost scope on the factor to be measured. Use the locking knobs at the aspect of the theodolite to preserve it aimed at the factor. Record the horizontal and vertical angles the use of the viewing scope observed at the theodolite’s aspect. With the help of electronic total station, measurement of slope distance, horizontal and vertical distance can accurately and precisely found out. Electronic total station gives the complete basic surveying exercise in order to appreciate how land survey measurements can be used in support of engineering construction and environmental restoration activities. Vertical angle and horizontal angle are accurately measured by electronic total station. Total station for levelling classified as the indirect levelling method and since it is judged that the method can maintain the considerable accuracy, now it has been increasingly used for many public works as road, airport and city etc. A total station is an electronic or optical instrument used in advanced and modern surveying. It is also used by archaeologists to record excavations as well as by police, crime scene investigators, private accident reconstructionist and insurance companies to take the measurements of scenes. Angles and distances are measured from the total station to points under survey and the co-ordinates (i.e. X.Y and Z or northing, easting and elevation.) of surveyed points relative to the total station position are further calculated by trigonometry and triangulation. Whatever data collected at the time of surveying can be downloaded from the total station to a computer and application software used to compute the results and generate a map of the surveyed area. Most modern total station instrument measure the angles by means of electro-optical scanning of extremely precise digital bar-codes etched on rotating glass cylinders or discs within the instrument. The total stations are capable of measuring angles to 0.5 arc-second. The total stations are mainly used by land surveyors and software is used to process the data and produce maps and 3-dimensions animation. It is also used in the area of mining surveying and also in the area of underground mining. New and advance total station production have a full set of the traditional surveying tools such as new GPS receivers and software. The new total station has high efficiency. simplicity and convenience in operation, low power consumption, small weight and sizes a provision to use on a tripod, in a backpack and on the car, a boat and other mobile objects. The new total station is also used in the disciplines of geodesy such as theoretical geodesy, physical geodesy, spheroidal geodesy, basic geodetic survey, celestial geodesy, topography, marine geodesy, applied geodesy and mining geodesy. Total station is advanced type of instrument and must commonly used in various work of surveying filed since it gives more accurate and precise results. Total station is specially made of three units such as an electronic theodolite an electronic measuring device (EDM) a microprocessor with memory unit With the help of total station, angles and distances from the instrument to the require points to be surveyed can be precisely determined. The angles and distances can be used to calculate the actual positions i.e. x y and z or northing, casting and elevation of surveyed points in absolute terms. Total station consists of a standard transit i.e. a telescope with cross hairs for sighting the require target or object. The telescope is attached to scales for measuring the angle of rotation of the telescope, relative to north as 0° and angle of inclination of the telescope relative to the horizontal as 0°. It also consists of an electronic distance measuring device (EDM) and electronic angle scanning coded scales of the horizontal and vertical circles are scanned electronically and after this require angles and distances are displayed digitally. Elevation or height difference, horizontal distance and the co-ordinates can automatically be calculated. It also has one provision of a digital read out of angles instead of a scale for getting accurate result. Since read-out is a continuous process, the angels can be crosschecked at any time. The total station has built in arrangement of EDM instrument which transmits an infrared beam which is reflected back to the instrument unit with the help of a prism. Most of the total station includes data recorders. The raw data of angles and distances and the coordinates of the require points sighed are recorded along with some additional information. Then this recorded data can be directly downloaded to a computer which helps in reducing the possible errors. The total station is mounted on a tripod and levelled before use, and prism is mounted on a pole of known height. The mounting bracket consists of aids for aiming the instrument. The total station includes the following parts: Foot screw Focusing battery Serial interface Tribrach base Keypad carrying handle Vertical drive Circular level display EDM transmitter Horizontal drive Optical sight Remote sensing is a method of collecting and interpreting information about terrain and other objects from a distance without being in physical contact with the objects. Remote sensing involves the use of electromagnetic energy for the characteristics determination of the object. In remote sensing, the imagery is obtained with a sensor. Special techniques are used in remote sensing to process and interpret remote sensing imagery to obtain conventional maps, resource surveys etc. It collects information about geology, geography, forestry agriculture etc. and has a vast application in exploration of natural resources. Remote sensing has application in the study of natural hazards such as earth quakes, landslides and land subsidence. In remote sensing, the use of electromagnetic energy for the determination of the characteristics of the object is basically involved. Detecting and recording of radiant energy reflected or emitted by objects or surface material. Various objects return the different amount and the kind of energy in different bands of electromagnetic spectrum which is incident upon it. There is interaction of electromagnetic energy with matter or object. It refers to sensing of electromagnetic radiation which is reflected, scattered or emitted from the object. A system which offers no flaws and which is actually do not exist is called as an ideal remote sensing system. Following are the basic components of an ideal remote sensing system. Basic components of an ideal remote sensing system. A uniform energy source A super sensor A non-interfering atmosphere Multiple data users A real-time data handling system The source which provides energy over all wavelengths at a constant high level of output irrespective of place and time is a uniform energy source. Super sensor is simple and reliable and it do not need virtually no power or space and it is accurate and economical to operate. This super sensor is highly sensitive to all wavelength providing spatially detailed data on the absolute brightness from a scene throughout the spectrum. It is the atmosphere which do not change or modify or conserve the energy from the source any how towards the earth surface or from the earth surface itself. The users have knowledge of both their respective areas and of remote sensing data acquisition and analysis techniques. The same set of data have various types of information for different users. This is such system in which the instant radiance versus wavelength response over a terrain element is produced. It further process into an interpretable format and recognize as a unique for the particular terrain element from which it receive. This processing provides timely information. Allowing quick updating of data of low efforts and cost. Supporting research activities which involves spatial data. Providing significant and efficient tool for collection, storage, recalling, analysis integrating, manipulation, overlaying the spatial data from single sources or many sources. Generating the information which is important for better logical decision making of complex analysis or queries involving geographical reference data to increase the efficiency of planners and decision makers. Eliminating redundant database and minimizing duplication. Answering the query by presenting the information in a format required by user. GIS is used to improve organizational integration. GIS is used to make better decision. GIS is used for making maps. GIS is used for every organizations of the defense industry is many nations around the world. Surveyor use precise instruments, procedures and computations to accurately locate and define geographic features while conducting field survey that range from cadastral to engineering construction layout. GIS is used as an interface for integrating and accessing massive amounts of location-based information in the public safety market. GIS software to study epidemiology; look at health care facilities and map any system that is visual or spatial including inside a patient body. GIS helps students and teachers engage in studies that require and for and promote critical thinking, integrated learning and = see the multiple intelligences at any grade level. Architect makes the design, planning in proper and precise way quickly with the help of GIS. GIS provides the analytical capabilities that form the hub of successful precision agriculture system. GIS lets farmers perform site-specific analyses of agronomic data. GIS technology enables telecommunications professionals to integrate location-based data into analysis and management processes in network planning and operations, marketing and sales, customer care, data management and many other planning and problem-solving tasks. GIS is used in libraries and museums, in education, in conservation of water and wastewater, in transportation, in universities, in mining and earth sciences and in other so many institutions and organizations.
Unit - 5
Modern Surveying Instruments
Q1) What are the ranges of Electromagnetic spectrum?
A1)
Q2) Explain Electronic Distance Measurement?
A2)
Q3) Explain how to use a theodolite?
A3)
Q4) What is the use of total station?
A4)
Q5) What is the field application of total station?
A5) Following are the field applications of the total station in the area of surveying and other area other then surveying.
Q6) Explain construction of total station?
A6)
Fig.: total Station
Q7) What are the importance of remote sensing?
A7)
Q8) Explain Basic principle of Remote sensing?
A8)
Q9) Explain an ideal remote sensing system?
A9)
1. A uniform energy source
2. A super sensor
3. A non-interfering atmosphere
Fig.: An ideal remote sensing system
4. Multiple data users
5. A real-time data handling system
Q10) What are the objectives of GIS?
A10) Following are the various objectives of GIS:
Q11) What are the advantages of GIS?
A11)
A GIS can link data sets together by common location of data, such as addresses, which help department and agencies to share their data. By creating a shared database, one department can get benefit from the work of another. In GIS, data can be collected once and used many times.
The old adage "better information leads to better decision" is true for GIS. A GIS is not just an automated decision-making system but a tool to analyze and map data in support of the decision-making process.
GIS is flexible enough to map of any kind of terrain; even the human body. GIS can map any data we wish to make. For example, GIS is used for mapping in which one can find individual feature of object the land like building antennas, towers and landscape etc.
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