INTRODUCTION
An electromagnetic bomb, or e-bomb, is a weapon designed to take advantage of this dependency. But instead of simply cutting off power in an area, an e-bomb would actually destroy most machines that use electricity.
Generators would be useless, cars wouldn't run, and there would be no chance of making a phone call. In a matter of seconds, a big enough e-bomb could thrust an entire city back 200 years or cripple a military unit. ..
An electromagnetic bomb is designed to disable electronics with an electromagnetic pulse (EMP) that can couple with electrical/electronic systems to produce damaging current and voltage surges by electromagnetic induction. The effects are usually not noticeable beyond the blast radius unless the device is nuclear or specifically designed to produce an electromagnetic pulse.
EFFECTS
These weapons are not directly responsible for the loss of lives, but can disable some of the electronic system on which industrialized nations are highly dependent.
Devices that are susceptible to EMP damage, from most to least vulnerable;
1. Integrated circuits (ICs), CPUs, silicon chips.
2. Transistors, Vacuum tubes (also known as thermionic valves.)
3. Inductors, motors.
Transistor technology is likely to fail and old vacuum equipments survive. However, different types of transistors and ICs show different sensitivity to electromagnetism: bipolar ICs and transistors are much less sensitive than FETs and especially MOSFETs. To protect sensitive electronics, a Faraday cage must be placed around the item. Some makeshift Faraday cages have been suggested, such as aluminum foil, although such a cage would be rendered useless if any conductors passed through, such as power cords or antennas.
The term electromagnetic pulse (EMP) has the following meanings:
1. Electromagnetic radiation from an explosion (especially a nuclear explosion) or an intensely fluctuating magnetic field caused by Compton-recoil electrons and photo electrons from photons scattered in the materials of the electronic or explosive device or in surrounding medium. The resulting electric and magnetic fields may couple with electrical/electronic systems to produce damaging current and voltage surges. See Electromagnetic Bomb for details on the damages resulting to electronic devices. The effects are usually not noticeable beyond the blast radius unless the devices are nuclear or specifically designed to produce an electromagnetic shockwave.
2. A broadband, high-intensity, short-duration burst of electromagnetic energy. In the case of a nuclear detonation or an asteroid impact, most of the energy of the electromagnetic pulse is distributed in the frequency band between 3Hz and 30 kHz.
PRACTICAL CONSIDERATION
The mechanism for a 400 km high altitude burst EMP gamma rays hit the atmosphere between 20-40 km altitude, ejecting electrons which are then deflected sideways by the earth’s magnetic field. This makes the electrons radiate EMP over area. Because of the curvature of earth’s magnetic field the USA, the maximum EMP occur south of the detonation and the minimum occurs to the north.
The worst of the pulse latest for only seconds, but any unprotected electrical equipment and anything connected to electrical cables, which act as giant lighting rods or antennas will be affected by the pulse. Older, vacuum tube (valve) based equipment is much less vulnerable to EMP; Soviet Cold War-era military aircraft often had avionics on vacuum tubes.
Many nuclear detonations have taken place using bombs dropped by aircraft. The aircraft that delivered the atomic weapons at Hiroshima and Nagasaki did not fall out of the sky due to damage to their electrical or electronic systems. This is simply because electrons (ejected from the air by gamma rays) are stopped quickly in normal air for bursts below 10 km, so they do not get a chance to be significantly deflected by the Earth's magnetic field (the deflection causes the powerful EMP seen in high altitude bursts), but it does point out the limited use of smaller burst altitudes for widespread EMP.
If the B-29 planes had been within the intense nuclear radiation zone when the bombs exploded over Hiroshima and Nagasaki, then they would have suffered effects from the charge separation (radial) EMP. But this only occurs within the severe blast radius for detonations below about 10 km altitude. EMP disruptions were suffered aboard KC-135 photographic aircraft flying 300 km from the 410 KT Bluegill and 410 KT Kingfish detonations (48 and 95 km burst altitude, respectively) in 1962, but the vital aircraft electronics then were far less sophisticated than today and did not down the aircraft.
Several major factors control the effectiveness of an EMP weapon. These are:
1. The altitude of the weapon when detonated;
2. The yield of the weapon;
3. The distance from the weapon when detonated;
Geographical depth or intervening geographical features,
Beyond a certain altitude a nuclear weapon will not produce any EMP, as the gamma rays will have had sufficient distance to disperse. In deep space or on worlds with no magnetic field (the moon or Mars for example) there will be little or no EMP. This has implications for certain kinds of nuclear rocket engines. See Project Orion.
WEAPON ALTIITUDE
How the peak EMP on the ground varies with the weapon yield and burst altitude. The yield here is the prompt gamma ray output measured in kilotons. This varies from 0.115–0.5% of the total weapon yield, depending on weapon design. The 1.4 Mt total yields 1962 Starfish Prime test had an output of 0.1%, hence 1.4 KT of prompt gamma rays. (The blue 'pre-ionization' curve applies to certain types of thermonuclear weapon, where gamma and x-rays from the primary fission stage ionize the atmosphere and make it electrically conductive before the main pulse from the thermonuclear stage. The pre-ionization in some situations can literally short out part of the final EMP, by allowing conduction current to immediately oppose the Compton current of electrons.)
A high-altitude nuclear detonation produces an immediate flux of gamma rays from the nuclear reactions within the device. These photons in turn produce high energy free electrons by Compton scattering at altitudes between (roughly) 20 and 40 km. These electrons are then trapped in the Earth's magnetic field, giving rise to an oscillating electric current. This current is asymmetric in general and gives rise to a rapidly rising radiated electromagnetic field called an electromagnetic pulse (EMP). Because the electrons are trapped essentially simultaneously, a very large electromagnetic source radiates coherently.
The pulse can easily span continent-sized areas, and this radiation can affect systems on land, sea, and air. The first recorded EMP incident accompanied a high-altitude nuclear test over the South Pacific and resulted in power system failures as far away as Hawaii. A large device detonated at 400–500 km (250 to 312 miles) over Kansas would affect all of the continental U.S. The signal from such an event extends to the visual horizon as seen from the burst point.
Thus, for equipment to be affected, the weapon needs to be above the visual horizon. Because of the nature of the pulse as a large, long, high powered, noisy spike, it is doubtful that there would be much protection if the explosion were seen in the sky just below the tops of hills or mountains.
The altitude indicated above is greater than that of the International Space Station and many low Earth orbit satellites. Large weapons could have a dramatic impact on satellite operations and communications; smaller weapons have less such potential.
WEAPONS YIELD
Typical nuclear weapon yields quoted in such scenarios are in the range of 20 megatons. This is roughly 1,000 times the sizes of the weapons the United States used in Japan at Hiroshima and Nagasaki.
WEAPONS DISTANCE
The major energy in an EMP is electromagnetic, and radiates out from the point of detonation in a sphere. EMP is electromagnetic radiation. The intensity of these fields decreases in proportion to the circumference and distance from explosion. The actual amount of EMP energy deposited per unit area is entirely different, and that falls off as the inverse-square of distance.
How the area affected depends on the burst altitude.
Radius in Miles
Circumference
Relative
Strength
10
62.83
100% or 1
20
125.66
50% or 1/2
30
188.50
33.3% or 1/3
251.32
40
25% or 1/4
The range of gamma rays in the atmosphere is assumed to be 10 miles, which is appropriate for a 1 megaton burst at an altitude of about 10 miles. The size of the perimeter of this circle grows in proportion to the radius of the circle, and so the electric field strength weakens as the circle grows. By simple mathematics the electrical field strength does not fall as the inverse square law, but is instead a simple inverse linear relationship.
The range of deposition of gamma rays would be smaller for a surface burst because of the greater air density, which shields the initial gamma rays that cause the EMP. Conversely, for a burst at greater altitudes, the range of the deposition would be far greater than 10 miles, because the gamma rays could travel much further in the low density air before being stopped. The actual energy deposited per unit area, if emitted from an isotropic point source, is always governed by the inverse-square law.
But the damaging effect of EMP is determined largely by the peak electric field (measured in volts/meter), which falls only inversely with distance. The amount of EMP energy passing through a unit of area is proportional to the square of the field strength. Within the range of gamma ray deposition, these simple laws no longer hold as the air is ionized and there are other EMP effects such as a radial (non-radiated) electric field due to the separation of Compton electrons from air molecules, and other complex phenomena. So its energy = 1/d^2
NON-NUCLEAR ELECTROMAGNETIC PULSE
Non-nuclear electromagnetic pulse (NNEMP) is an electromagnetic pulse generated without use of nuclear weapons. There are a number of devices to achieve this objective, ranging from a large low-inductance capacitor bank discharged into a single-loop antenna or a microwave generator to an explosively pumped flux compression generator. To achieve the frequency characteristics of the pulse needed for optimal coupling into the target, wave-shaping circuits and /or microwave generators are added between the pulse source and the antenna. A vacuum tube particularly suitable for microwave conversion of high energy pulses is the victor.
A right frond view of a Boeing E-4 advanced airborne command post on the electromagnetic pulse (EMP) simulator for testing.
Non-nuclear electromagnetic pulse (NNEMP) generators can be carried as a payload of bombs and cruise missiles, allowing construction of electromagnetic bombs with diminished mechanical, thermal and ionizing radiation effects and without the political consequences of deploying nuclear weapons.
NNEMP generators also include large structures built to generate EMP for testing of electronics to determine how well it survives EMP. In addition, the use of ultra-wideband radars can generate EMP in areas immediately adjacent to the radar; this phenomenon is only partly understood.
USS Estocin (FFG-15) moored near an Electro Magnetic Pulse Radiation Environmental Simulator for ship (EMPRESS) facility.
CONCLUSION
An electromagnetic Bomb is designed to disable electronics with an electromagnetic pulse (EMP) that can couple with electrical/electronic system to produce damaging current and voltage surges by electromagnetic induction. The effects are usually not noticeable beyond the blast radius unless the device is nuclear or specifically designed to produce an electromagnetic pulse.
REFERENCES
1. http://www.wikipedia.com/
2. http://www.answers.com/
3. WWW.IEEE.ORG/MDH.HTML
4. http://www.gogle.com/
Saturday, September 20, 2008
Total station
INTRODUCTION
A total station is an optical instrument used a lot in modern surveying and, in a minor way, as well as by police, crime scene investigators, private accident deconstructionists and insurance companies to take measurements of scenes. It is a combination of an electronic Theodolite (transit), an electronic distance meter (EDM) and software running on an external computer known as a data collector.
The original name of Total-station was electronic tachometer, but Hewlett-Packard introduced the name Total-station over 30 years ago and the name immediately caught on with the profession.
With a total station one may determine angles and distances from the instrument to points to be surveyed. With the aid of trigonometry and triangulation, the angles and distances may be used to calculate the coordinates of actual positions (X, Y, and Z or northing, easting and elevation) of surveyed points, or the position of the instrument from known points, in absolute terms.
Type of Total-station
In the early days, three classes of total stations were available-manual, semiautomatic and automatic.
Manual Total-station:-
It was necessary to read the horizontal and vertical angles manually in this of instrument. The only value that could be read electronically was the slope distances.
Semiautomatic Total-station:-
The user had to manually read the horizontal circle for these instruments, but the vertical circle readings were shown digitally. Slope distances were measured electronically and the instruments could, in most cases, be used to reduce the values to horizontal and vertical components.
Automatic Total-station:-
This type is the most common Total-station used now days. They sense both the horizontal and vertical angles electronically and measure the slope distances, compute the horizontal and vertical components of those distances, and determine the co-ordinates of observed points. The co-ordinates information obtained can either be stored in the total-stations memory or by using an external data collector.
PARTS OF A TOTAL STATION
I. Optical plummet
II. Display
III. Battery compartment
IV. Leveling tube
V. Leveling screws
VI. Vertical clamp
VII. Telescope
VIII. Horizontal clamp
FIELD EQUIPMENTS
Modern electronic survey equipment requires surveyor to be more maintenance conscious than they were in the past. They have to take care about power sources, downloading data and integrity of data, including whether or not the instruments and accessories are accurately adjusted and in good form. When setting up a crew to work with total-station and a data collector, it is helpful to supply the party chief with a checklist to help the crew maintain its assigned equipment and handle the collected data upon returning to the office. It is also important that each crew should be supplied with all necessary equipment and supplies. These should be stored in an organized and easily accessible manner.
Preparing an equipment list carefully will assure the survey crew a sufficient equipment inventory to meet the general needs of boundary, layout, and topographic surveys. This procedure will confine what are needs to maximize productivity when using a total station with a data collector.
The maximum equipment inventory required is as follows:
1. Total-station set
a. Total-station instrument in a hard case
b. Battery charger
c. Extra battery
d. Memory module/card, serial cable
e. Rain cover
f. User manuals
g. Tripod
h. Tape measure
2. Prism set
a. Prism
b. Prism holder
c. Centering rod
3. Back sight set
a. Prism
b. Prism holder
c. Prism carrier
d. Tribrach
4. Data processing
a. Laptop computer with serial port or USB port
b. Serial cable or USB-serial adaptor
c. Terminal application
d. Application program: MS Excel, Adobe illustrator, etc.
e. Data backup device and media (Zip, memory card, etc.)
5. Survey tools
a. Stakes, nails, paint, marker
b. Hammer
c. Thermometer
d. A pair of radio (with hand-free headsets)
e. Clipboard, field note, pen
f. Compass
g. GPS
Temporary adjustment of a total-station
Setting-up the instrument:-
Extend the legs of the tripod as far as is required and tighten the screws firmly.
Set-up the tripod so that the tripod plate is as horizontal as possible and the legs of the tripod are firm in the ground.
Now, and only now, place the instrument on the tripod and secure it with the central fixing screw.
Leveling-up the instrument:-
After setting up the instrument, level it up approximately with the bull’s-eye bubble.
Turn two of the foot-screws together in opposite directions. The index finger of your right hand indicates the direction in which the bubble should move.
Now use the third food-screw to centre the bubble.
To check, rotate the instrument 180o. Afterwards, the bubble should remain within the setting circle. If it does not, then readjustment is required (refer to the user manual.)
For a level, the compensator automatically takes care of the final leveling up.
The compensator consists basically of a thread-suspended mirror that directs the horizontal light beam to the centre of the crosshair even if there is residual title in the telescope.
If now you lightly lap a leg of the tripod, then you will see how the line of sight swings about the staff reading and always steadying at the same point. This is the way to test whether or not compensator can swing freely.
SETTING UP A BACK SIGHT:-
A back sight is a reference point for the horizontal angle. At the beginning of a new survey, a back sight can be set at an arbitrary point and marked. The best way to set up a back sight is to use a prism carrier and a tribrach on a tripod. The procedure for leveling up and centering of the prism is the same as that for the total-station. If there is no plummet in the tribrach and the prism carrier, use the plummet of the total-station and then exchange the total station above the tribrach with a prism carrier. A prism should be put right on the reference point when sighting is possible from the total station.
Azimuth Mark:-
An Azimuth Mark is a back sight without a prism. It should be geometric point or a vertical lane to aim at, with precision. Once a nice azimuth mark is found on the telescope, keep a detailed sketch and comments in the field book.
An azimuth mark may substitute for a back sight for certain total-stations, in case it is not necessary to define the error. Some CPU and data processing applications to require back sight, setting up of additional azimuth marks beside the back sight is useful to check whether the configuration has not gone wrong.
MEASUREMENT WITH TOTAL-STATION
When both the total-station and back sight are finally leveled and centered, the hardware setup is over and the software setup is to be started. The software setup of a total station differs from one make to another. One has to follow the user’s manual of each instrument. Most total stations memorize these settings, but it is better to check through he setup menu in order to avoid a false setting.
System: Choose appropriate existing interfaced for data output
Angle Measurements: tilt correction/tilt compensator (2 axis)
Horizontal angle increments: At right angle (clockwise)
Unit setting: Angle in degrees/min/sec, distance in meter, temperature in 0C and pressure in hPa
EDM settings: Select IR laser, fine measuring mode, use RL with caution. Set appropriate value for the prism constant.
Atmospheric Parameters: Get ppm for the diagram from the manual of the equipment or let the total station calculate from hPa and degree centigrade
Communications: Set all parameters the same for a total station and data logger/PC. They are baud rate, data bits, parity, end mark and stop bits. Refer the manual for each device.
ADVANTAGES OF TOTAL-STATION
The advantages of total-station include;
I. Quick setting of the instrument on the tripod using laser plummet
II. On-board area computation program to compute the area of the field
III. Greater accuracy in area computation because of the possibility of taking arcs in area computation
IV. Graphical view of plots and land for quick visualization
V. Coding to do automated mapping. As soon as the field jobs are finished, the map of the area with dimensions is ready after data transfer
VI. Enormous plotting and area computation at any user required scale
VII. Integration of database
VIII. Automation of old maps
IX. Full GIS creation
X. Location language support
PORRO–PRISM Double-PORRO-prism
DISADVANTAGES OF TOTAL STATION:-
I. Their use does not provide hard copies of field notes. Hence it may be difficult for the surveyor to look over and check the work while surveying.
II. For an overall check of the survey, it will be necessary to return to the office and preparing the drawings using appropriate software.
III. They should not be used for observation of the sun, unless special filters, such as the Troelof’s prism, are used. If not, the EDM part of the instrument will be damaged.
IV. The instrument is costly, and for conducting surveys using total station, skilled personnel are required.
INSTRUMENT ERRORS IN THE TOTAL STATION
Ideally, the total station should meet the following requirements:
a. Line of sight ZZ perpendicular to tilting axis KK
b. Tilting axis KK perpendicular to vertical axis VV
c. Vertical-circle reading precisely zero at the zenith
If these conditions are not met, the following terms are used to discribe the particular errors:
a. Line-of-sight errors. Or collimation error c
b. Tilting-axis error a deviation from the right angle between the tilting axis and the vertical axis
c. Vertical-axis tilt tangle user manual. Vertical-axis tilt does rate as begin an instrument has not been adequately leveled up, and measuring in both telescope faces cannot eliminate it. It influences on the measurement of the horizontal and vertical angle is automatically corrected by means of a two-axis compensator.
d. Height-index error (the angle between the zenith direction zero reading of the vertical circle ,i.e. the vertical circle reading when using a horizontal line of sight) .is not 100gon (900 but 100gon )
By measuring in both laces and then averaging the index error is eliminated it can also be determined and stored.
The effects of these three errors on measurements of horizontal angles Increase with the height difference between the largest points.
Taking measurements in both telescope faces eliminates line –of-sight errors and tilting errors .The line-of-sight error (and for highly precise total stations, also the tilting errors ,which is generally very small) can also be determined and stored .These errors are then taken into consideration automatically whenever an angle is measured, and then it is possible to take measurements practically free of error ,and telescope face The determination of these errors ,and their storage are described in the appropriate.
CONCLUSION
A total station is an optical instrument used a lot in modern surveying and, in a minor way, as well as by police, crime scene investigators, private accident deconstructionists and insurance companies to take measurements of scenes. Now a day it is the most useful instrument in the field of survey. Its speed and accuracy is very helpful to the surveyor for taking measurement.
REFERENCE
1. Advanced Surveying (Satheesh Gopi, R. Sathikumar & N. Madhu)
2. www.Gogle.com
3. www.wikipeadia.com
A total station is an optical instrument used a lot in modern surveying and, in a minor way, as well as by police, crime scene investigators, private accident deconstructionists and insurance companies to take measurements of scenes. It is a combination of an electronic Theodolite (transit), an electronic distance meter (EDM) and software running on an external computer known as a data collector.
The original name of Total-station was electronic tachometer, but Hewlett-Packard introduced the name Total-station over 30 years ago and the name immediately caught on with the profession.
With a total station one may determine angles and distances from the instrument to points to be surveyed. With the aid of trigonometry and triangulation, the angles and distances may be used to calculate the coordinates of actual positions (X, Y, and Z or northing, easting and elevation) of surveyed points, or the position of the instrument from known points, in absolute terms.
Type of Total-station
In the early days, three classes of total stations were available-manual, semiautomatic and automatic.
Manual Total-station:-
It was necessary to read the horizontal and vertical angles manually in this of instrument. The only value that could be read electronically was the slope distances.
Semiautomatic Total-station:-
The user had to manually read the horizontal circle for these instruments, but the vertical circle readings were shown digitally. Slope distances were measured electronically and the instruments could, in most cases, be used to reduce the values to horizontal and vertical components.
Automatic Total-station:-
This type is the most common Total-station used now days. They sense both the horizontal and vertical angles electronically and measure the slope distances, compute the horizontal and vertical components of those distances, and determine the co-ordinates of observed points. The co-ordinates information obtained can either be stored in the total-stations memory or by using an external data collector.
PARTS OF A TOTAL STATION
I. Optical plummet
II. Display
III. Battery compartment
IV. Leveling tube
V. Leveling screws
VI. Vertical clamp
VII. Telescope
VIII. Horizontal clamp
FIELD EQUIPMENTS
Modern electronic survey equipment requires surveyor to be more maintenance conscious than they were in the past. They have to take care about power sources, downloading data and integrity of data, including whether or not the instruments and accessories are accurately adjusted and in good form. When setting up a crew to work with total-station and a data collector, it is helpful to supply the party chief with a checklist to help the crew maintain its assigned equipment and handle the collected data upon returning to the office. It is also important that each crew should be supplied with all necessary equipment and supplies. These should be stored in an organized and easily accessible manner.
Preparing an equipment list carefully will assure the survey crew a sufficient equipment inventory to meet the general needs of boundary, layout, and topographic surveys. This procedure will confine what are needs to maximize productivity when using a total station with a data collector.
The maximum equipment inventory required is as follows:
1. Total-station set
a. Total-station instrument in a hard case
b. Battery charger
c. Extra battery
d. Memory module/card, serial cable
e. Rain cover
f. User manuals
g. Tripod
h. Tape measure
2. Prism set
a. Prism
b. Prism holder
c. Centering rod
3. Back sight set
a. Prism
b. Prism holder
c. Prism carrier
d. Tribrach
4. Data processing
a. Laptop computer with serial port or USB port
b. Serial cable or USB-serial adaptor
c. Terminal application
d. Application program: MS Excel, Adobe illustrator, etc.
e. Data backup device and media (Zip, memory card, etc.)
5. Survey tools
a. Stakes, nails, paint, marker
b. Hammer
c. Thermometer
d. A pair of radio (with hand-free headsets)
e. Clipboard, field note, pen
f. Compass
g. GPS
Temporary adjustment of a total-station
Setting-up the instrument:-
Extend the legs of the tripod as far as is required and tighten the screws firmly.
Set-up the tripod so that the tripod plate is as horizontal as possible and the legs of the tripod are firm in the ground.
Now, and only now, place the instrument on the tripod and secure it with the central fixing screw.
Leveling-up the instrument:-
After setting up the instrument, level it up approximately with the bull’s-eye bubble.
Turn two of the foot-screws together in opposite directions. The index finger of your right hand indicates the direction in which the bubble should move.
Now use the third food-screw to centre the bubble.
To check, rotate the instrument 180o. Afterwards, the bubble should remain within the setting circle. If it does not, then readjustment is required (refer to the user manual.)
For a level, the compensator automatically takes care of the final leveling up.
The compensator consists basically of a thread-suspended mirror that directs the horizontal light beam to the centre of the crosshair even if there is residual title in the telescope.
If now you lightly lap a leg of the tripod, then you will see how the line of sight swings about the staff reading and always steadying at the same point. This is the way to test whether or not compensator can swing freely.
SETTING UP A BACK SIGHT:-
A back sight is a reference point for the horizontal angle. At the beginning of a new survey, a back sight can be set at an arbitrary point and marked. The best way to set up a back sight is to use a prism carrier and a tribrach on a tripod. The procedure for leveling up and centering of the prism is the same as that for the total-station. If there is no plummet in the tribrach and the prism carrier, use the plummet of the total-station and then exchange the total station above the tribrach with a prism carrier. A prism should be put right on the reference point when sighting is possible from the total station.
Azimuth Mark:-
An Azimuth Mark is a back sight without a prism. It should be geometric point or a vertical lane to aim at, with precision. Once a nice azimuth mark is found on the telescope, keep a detailed sketch and comments in the field book.
An azimuth mark may substitute for a back sight for certain total-stations, in case it is not necessary to define the error. Some CPU and data processing applications to require back sight, setting up of additional azimuth marks beside the back sight is useful to check whether the configuration has not gone wrong.
MEASUREMENT WITH TOTAL-STATION
When both the total-station and back sight are finally leveled and centered, the hardware setup is over and the software setup is to be started. The software setup of a total station differs from one make to another. One has to follow the user’s manual of each instrument. Most total stations memorize these settings, but it is better to check through he setup menu in order to avoid a false setting.
System: Choose appropriate existing interfaced for data output
Angle Measurements: tilt correction/tilt compensator (2 axis)
Horizontal angle increments: At right angle (clockwise)
Unit setting: Angle in degrees/min/sec, distance in meter, temperature in 0C and pressure in hPa
EDM settings: Select IR laser, fine measuring mode, use RL with caution. Set appropriate value for the prism constant.
Atmospheric Parameters: Get ppm for the diagram from the manual of the equipment or let the total station calculate from hPa and degree centigrade
Communications: Set all parameters the same for a total station and data logger/PC. They are baud rate, data bits, parity, end mark and stop bits. Refer the manual for each device.
ADVANTAGES OF TOTAL-STATION
The advantages of total-station include;
I. Quick setting of the instrument on the tripod using laser plummet
II. On-board area computation program to compute the area of the field
III. Greater accuracy in area computation because of the possibility of taking arcs in area computation
IV. Graphical view of plots and land for quick visualization
V. Coding to do automated mapping. As soon as the field jobs are finished, the map of the area with dimensions is ready after data transfer
VI. Enormous plotting and area computation at any user required scale
VII. Integration of database
VIII. Automation of old maps
IX. Full GIS creation
X. Location language support
PORRO–PRISM Double-PORRO-prism
DISADVANTAGES OF TOTAL STATION:-
I. Their use does not provide hard copies of field notes. Hence it may be difficult for the surveyor to look over and check the work while surveying.
II. For an overall check of the survey, it will be necessary to return to the office and preparing the drawings using appropriate software.
III. They should not be used for observation of the sun, unless special filters, such as the Troelof’s prism, are used. If not, the EDM part of the instrument will be damaged.
IV. The instrument is costly, and for conducting surveys using total station, skilled personnel are required.
INSTRUMENT ERRORS IN THE TOTAL STATION
Ideally, the total station should meet the following requirements:
a. Line of sight ZZ perpendicular to tilting axis KK
b. Tilting axis KK perpendicular to vertical axis VV
c. Vertical-circle reading precisely zero at the zenith
If these conditions are not met, the following terms are used to discribe the particular errors:
a. Line-of-sight errors. Or collimation error c
b. Tilting-axis error a deviation from the right angle between the tilting axis and the vertical axis
c. Vertical-axis tilt tangle user manual. Vertical-axis tilt does rate as begin an instrument has not been adequately leveled up, and measuring in both telescope faces cannot eliminate it. It influences on the measurement of the horizontal and vertical angle is automatically corrected by means of a two-axis compensator.
d. Height-index error (the angle between the zenith direction zero reading of the vertical circle ,i.e. the vertical circle reading when using a horizontal line of sight) .is not 100gon (900 but 100gon )
By measuring in both laces and then averaging the index error is eliminated it can also be determined and stored.
The effects of these three errors on measurements of horizontal angles Increase with the height difference between the largest points.
Taking measurements in both telescope faces eliminates line –of-sight errors and tilting errors .The line-of-sight error (and for highly precise total stations, also the tilting errors ,which is generally very small) can also be determined and stored .These errors are then taken into consideration automatically whenever an angle is measured, and then it is possible to take measurements practically free of error ,and telescope face The determination of these errors ,and their storage are described in the appropriate.
CONCLUSION
A total station is an optical instrument used a lot in modern surveying and, in a minor way, as well as by police, crime scene investigators, private accident deconstructionists and insurance companies to take measurements of scenes. Now a day it is the most useful instrument in the field of survey. Its speed and accuracy is very helpful to the surveyor for taking measurement.
REFERENCE
1. Advanced Surveying (Satheesh Gopi, R. Sathikumar & N. Madhu)
2. www.Gogle.com
3. www.wikipeadia.com
ULTRA SONIC MOTOR
ULTRA SONIC MOTOR
Ultra sonic motor is a newly developed motor, and it has excellent performance and many useful features, e.g.: high-torque density, low speed, compactness in size, no electromagnetic interferences, and so on. Ultra sonic motor is a kind of Piezo motor. The proposed speed control scheme is assumed for these applications because they require quick and precise speed control of actuators for various load conditions. A speed control method of ultra sonic motor using adaptive control is proposed. Artificial Neural Network (ANN), which follows the biological neural cells in brain, consists of a number of neurons and weighted links, and it has a good potential for control applications because it can approximate the non-linear input-output mapping of the plant. Accordingly, Artificial Neural Network has been applied widely in the field of power electronics control. In this paper a three layer neural network for speed controller is adopted, and the weights of the links are updated using the general back propagation in order to reduce the speed error at each sampling period. In general, the speed of Ultra sonic motor can be controlled by driving frequency, applied voltage, and phase difference of applied voltages. This paper adopts the driving frequency as control input in order to simplify the drive system.
Ultra sonic motor is a newly developed motor, and it has excellent performance and many useful features, e.g.: high-torque density, low speed, compactness in size, no electromagnetic interferences, and so on. Ultra sonic motor is a kind of Piezo motor. The proposed speed control scheme is assumed for these applications because they require quick and precise speed control of actuators for various load conditions. A speed control method of ultra sonic motor using adaptive control is proposed. Artificial Neural Network (ANN), which follows the biological neural cells in brain, consists of a number of neurons and weighted links, and it has a good potential for control applications because it can approximate the non-linear input-output mapping of the plant. Accordingly, Artificial Neural Network has been applied widely in the field of power electronics control. In this paper a three layer neural network for speed controller is adopted, and the weights of the links are updated using the general back propagation in order to reduce the speed error at each sampling period. In general, the speed of Ultra sonic motor can be controlled by driving frequency, applied voltage, and phase difference of applied voltages. This paper adopts the driving frequency as control input in order to simplify the drive system.
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