Total Station And Its Applications In Surveying 1. INTRODUCTION • The Total station is designed for measuring of slant distances, horizontal and vertical angles and elevations in topographic and geodetic works, tachometric surveys, as well as for solution of application geodetic tasks. The measurement results can be recorded into the internal memory and transferred to a personal computer interface. • The basic properties are unsurpassed range, speed and accuracy of measurements. Total stations are developed in view of the maximal convenience of work of the user. High-efficiency electronic tachometers are intended for the decision It has the broad audience for sole of industrial problems. • Angles and distances are measured from the total station to points under survey, and the coordinates (X, Y, and Z or northing, easting and elevation) of surveyed points relative to the total station position are calculated using trigonometry and triangulation. • Data can be downloaded from the total station to a computer and application software used to compute results and generate a map of the surveyed area. • A total station is an electronic/optical instrument used in modern surveying. It is also used by archaeologists to record excavations as well as by police, crime scene investigators, private accident Reconstructionists and insurance companies to take measurements of scenes. The total station is an electronic theodolite (transit) integrated with an electronic distance meter (EDM), plus internal data storage and/or external data collector. • The purpose of any survey is to prepare maps, control points formed a basic requirement for the preparation of these maps. • There are several numbers of methods like traverse, triangulation etc., to provide these control points. • Whatever the method the provision of control points, includes the measurement of two entities( Distance and Angle). • Again, distance can be measured by using various instruments like chain, tape. • Linear Tap. • Gunter’s chain (20m and 30m). • Steel band(20m and 30m). • Inver tap. • Hunter Short Base (80m). • Electronic Distance Measurement Instruments, Total station and GPS. • Angle can be measured by using a THEODOLITE. • Once distance and angular measurement is over computation is performed to provide the control points. A combination of all the three results in a powerful instrument called TOTAL STATION.Hence, the TOTAL STATION is an instrument which consists of the following: i) Distance measuring instrument (EDM). ii) An angle measuring instrument (Theodolite). iii) A simple microprocessor. 1.2. INSTRUMENTATION: It consists of an EDM, Theodolite, Microprocessor combined into one. It also has a memory card to store the data. It also consists of battery socket which houses the battery. A fully charged battery works for about 3 to 5 hrs continuously. Figure 1: Different Parts of Total Station 1.3. ACCURACY OF A TOTAL STATION: Accuracy depending upon the instrument and varies from instrument to instrument 1.The angular accuracy varies from1″ to 20 ″. 2.Distance accuracy depends upon two factors. Instrumental error which ranges from + / – 10mm to + / – 2mm. b) Error due to the length of measurement. It can be from + / – 10mm to + / – 2mm per kilometre. 1 prism, 2.5–2.7 km2 prisms 5-7 km3 prisms 10-12 kmNIKONOne second+ / – 2mm/km or 2ppmTriple the number of prisms double the distance.LEICAOne second SOKKIAOne second. 1.3.1. ACCURACY & PRECISION • Precision is the reproducibility of the measurement. • Accuracy is how close the measured position is to the actual location Measurement of distance is accomplished with a modulated microwave or infrared carrier signal, generated by a small solid-state emitter within the instrument’s optical path, and reflected by a prism reflector or the object under survey. The modulation pattern in the returning signal is read and interpreted by the onboard computer in the total station. The distance is determined by emitting and receiving multiple frequencies, and determining the integer number of wavelengths to the target for each frequency. Most total stations use purpose-built glass Porro prism reflectors for the EDM signal, and can measure distances to a few kilometers. Reflectorless total stations can measure distances to any object that is reasonably light in color, to a few hundred meters. Principle: Given the co-ordinate of the instrument position and bearing of a backward station the co-ordinates of any other point can be computed. 1.3.2. TOTAL STATION CAN BE USED 1.4. ACCESSORIES FOR TOTAL STATION With approximately more than 40 different models are available to choose, they are currently the dominant instrument in surveying. The EDM instrument component installed in a Total Station is relatively small but still has distance ranges adequate for most work. Lengths up to about 2 km can be measured with a single prism, and up to about 6 to 7 km with triple prism. The angle resolution of available Total Stations varies from as low as a half-second for precise instruments suitable for control surveys, up to 20″ for instruments made specifically for construction stakeout . 1.5. FUNCTIONS PERFORMED BY TOTAL STATIONS Total Stations, with their micro processors, can perform a variety of functions and computations, depending on how they are programmed. The capabilities vary with different instruments, but some standard computations include: • Averaging multiple angle and distance measurements. • Correcting electronically measured distances from prism constant, atmospheric pressure, and temperature. • Making curvature and refraction corrections to elevations determine by trigonometric levelling. • Reducing slope distances to their horizontal and vertical components. • Calculating point elevations from the vertical distance components (supplemented with keyboard input of instrument and reflector heights). • Computing coordinates of survey points from horizontal angle and horizontal distance. o Averages multiple angle measurements. o Averages multiple distance measurements. o Computes horizontal and vertical distances. o Corrections for temp, pressure and humidity. o Computes inverses, polars, resections. o Computes X, Y and Z coordinates. 1.6.OPERATION OF TOTAL STATION 1.7. REMOTELY OPERATED TOTAL STATION (ROBOTIC) 1.7.1. Features Include: 1.8. Applications of Total Station There are many other facilities available, the total station can be used for the following purposes. • Detail survey i.e., data collection. • Control Survey (Traverse). • Height measurement (Remove elevation measurement- REM). • Fixing of missing pillars (or) Setting out (or) Stake out. • Resection. • Area calculations, etc. • Remote distance measurement (RDM) or Missing line measurement (MLM). 1.8.1. Data Collection Option 1.8.2. Detail Survey 1.8.3. CONTROL SURVEY / TRAVERSE 1.8.4. TRAVERSE 1.8.5. CLASSIFICATION OF TRAVERSE (BASED ON ACCURACY & BASED ON INSTRUMENT USED ): 1.8.6. Classification of Traverse: • Open traverse: Starts from a known control point and ends at unknown point. • Closed traverse: Starts from and ends at known control points. • Closed Circuit traverse: Starts from and ends at known control points. 1.8.7. APPLICATION OF TRAVERSE 1.8.8. THE REFERENCE LINE MAY BE: Azimuth Grid Bearing Magnetic Bearing 1.8.9. AZIMUTH AND GRID BEARIN 1.9. REMOTE ELEVATION MEASUREMENT (REM) 1.9.1. REMOTE DISTANCE MEASUREMENT (RDM) OR MISSING LINE MEASUREMENT (MLM) 1.9.2. FIXING OF MISSING PILLARS (OR) SETTING OUT (OR) STAKE OUT 1.9.3. RESECTION 1.9.4. AREA CALCULATION 1.9.5. USES OF TOTAL STATION The uses of Total Station are as follows: • Mine Survey • Cadastral Survey • Engineering Survey • Large Scale Survey • Road / Rail / Canal Survey Some total stations also have a GNSS interface which combines the advantages of these two technologies (GNSS – line of sight not required between measured points; Total Station – high precision measurement especially in the vertical axis compared with GNSS) and reduce the consequences of each technology’s disadvantages (GNSS – poor accuracy in the vertical axis and lower accuracy without long occupation periods; Total Station – requires line of sight observations and must be set up over a known point or with line of sight to 2 or more points with known location). gisresources/total-station-and-its-applications-in-surveying/ ***
Posted on: Sun, 03 Aug 2014 11:58:16 +0000
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