Lesson Note On Maintenance of Surveying Equipments

Maintenance of Surveying Equipment
	Surveying equipment is being used under most stressful conditions. The equipment is exposed to extreme weather conditions, used in dusty construction areas and is subject to bumpy transportation. Proper care in the method by which equipment is used, stored, transported, and adjusted is a major factor in the successful completion of the survey. Lack of good maintenance practices not only causes unjustified replacement costs, but also can serious the efficiency and accuracy of the entire survey. General Care and Maintenance of Surveying Equipment and Tools Surveying instruments, which include theodolites, levels, total stations, electronic measuring devices, and GPS receivers, are designed and constructed to provide years of reliable use. The shafts, spindles, pendulums, and electronics of precision instruments, although constructed for rugged field conditions, can be damaged by one careless act, or continued negation prescribed procedures for use, care, and adjustment of the instrument.
Each new instrument is furnished with an operator’s manual. The manual contains a description of the instrument, specifications of its various components and capabilities, and applications. The manual also contains basic instructions for use of the instrument and describes recommended servicing and adjusting methods. The operator’s manual should be kept with the instrument at all times. Each operator should thoroughly study the manual prior to use of he instrument, particularly whenever prescribed field adjustments are to be made. If the manual is lost, stolen, or damaged beyond use, a replacement copy should be obtained as soon as practicable. The following general principles of care and servicing should be applied as a routine matter for all survey equipment and supplies. §  All equipment and tools should be kept as clean and dry as practicable, particularly if they are to be transported or stored for any length of time. §  Wooden surfaces should be wiped clean of caked mud or moisture prior to returning the equipment to the vehicle. The original painted or varnished surfaces should be repaired as often as needed to keep moisture from entering the wood. §  Metal surfaces should be cleaned and wiped as dry as practicable. A coat of light oil should be applied to tapes and the metal parts of tools to prevent rusting during storage. Excess oil should be wiped off. Routine Care of Surveying Instruments. §  Before making the first set up of the day, visually inspect the instrument for cracks, bumps, and dents. Check the machined surfaces and the polished faces of the lenses and mirrors. Try the clamps and motions for smooth operation (absence of binding or gritty sound). §  Frequently clean the instrument externally. Any accumulation of dirt and dust can scratch the machined or polished surface and cause friction or sticking in the motions. §  Dirt and dust should be removed only with a clean soft cloth or with a camel hair brush. §  Non-optical parts may be cleaned with a soft cloth or clean chamois. §  Clean the external surfaces of lenses with a fine lens brush and , if necessary, use a dry lens tissue. Do not use silicon treated tissues, as they can damage the coated optics. It is permissible to breath on the lens before wiping it, but liquids, such as oil, benzene, water, etc., should never be used for cleaning purposes. DO NOT loosens or attempt to clean the internal surface of any lens. §  Cover an instrument whenever it is uncased and not being used for any length of time, particularly if there is dust or moisture in the air. After an instrument has been used in damp or extremely cold situation, special precautions must be taken to prevent condensation of moisture inside of the instrument. When working with the instrument in cold weather, it should be left in the carrying case in the vehicle overnight. If stored in a heated room overnight, the instrument must be removed from the carrying case. If the instrument is wet or frost covered it should be remove it from its case, and leave it at room temperature to dry out. 3. Care in Transporting Surveying Equipment. Vehicular Transport §  The major damage to equipment and tools occurs when they are being placed into or taken out of the survey vehicle. Other damage occurs during transport, when equipments is jostled against other tools or equipment. Compartments (lined with carpeting, when possible) should be provided to keep equipment and supplies separated. This not only keeps the equipment from being damaged, it facilitates finding such items more rapidly. Heavier items should be carried in the lower parts of vehicles and they should never be in direct contact with other tools or equipment below them. §  The care, organization, and general housekeeping of a vehicle are good indications of the attitude of the entire survey crew. Keep passenger compartments free of unnecessary clutter and equipment. Any equipment or material carried in the passenger compartment should be firmly secured. §  Transport and store instrument in positions that are consistent with the carrying case design. Many instrument cases indicate the position in which they should be transported. Treat optical targets, prisms, and staffs with the same consideration. §  Transport the instruments in their carrying cases placed in a compartment cushioned with firm poly foam or similar material to protect them from jolting or excessive vibrations. §  Remember, loose equipment, out of place tools, and general clutter not only contributes to damage of the items, they also waste crew time in locating them and are a safety hazard. Casing and Uncasing Before removing an instrument, study the way it is placed and secured in the case. The instrument must be replaced in the same position when returned to the case. In removing the instrument from the case, carefully grip it with both hands, but do not grip the vertical circle standard or where pressure will be exerted on tubular or circular level vials. Field Transport of Surveying Instrument Do not “shoulder” or carry a tripod mounted theodolite or electronic distance measuring equipment (EDM). These instruments should always be removed from the tripod and secured in their carrying cases when moved. These precautions are necessary because the center spindle (center spigot or standing axis) of a theodolite is hollow and relatively short. When carried horizontally while on the tripod, the alidade’s weight is an excessive load for the hollow centerpiece to bear. Instrument damage can result if the above precautions are ignored. Also, the instrument fastener can break, causing the theodolite to fall. 4. Care During Instrument Setups Whenever possible, select instrument stations where operation is not dangerous to the instrument operator, the crew, or the instrument. Select stable ground for the tripod feet. Do not set an instrument closely in front of, or behind, a vehicle or equipment which is likely to move. Take a safe route to all setups. At the site, firmly plant the tripod with its legs widespread. Push along the legs, not vertically, downward. On smooth surfaces, use some type of tripod leg restrainer to keep the legs from sliding outward. Always have the tripod firmly set over the point before removing the instrument from its carrying case. Immediately secure the instrument to the tripod with the instrument fastener. Never leave an instrument or its tribrach on the tripod without securing either to the tripod. Moderate pressure on the fastener screw is sufficient. Excessive tightening causes undue pressure on the foot screws and on the tribrach spring plate. Make sure the tribrach clamp is in the lock position. 5. Adjustments of Surveying Instruments. Field Adjustments The crew leader should develop a set of test procedure to be used frequently for elimination of gross errors. Such tests should include a check of items such as the level, optical plummet, and tripod. In the field, adjustments should only be made when the instrument results are poor or require excessive manipulation. Normally, each instrument should be periodically checked at a facility where the best conditions for testing are possible. Only the adjustments described in the manual for the instrument should be made in the field or shop. Do not “field strip” (dismantle) instruments. Major Adjustments When an instrument has been damaged or otherwise requires major adjustments, it will need to be sent to an authorized repair shop. The instrument should be accompanied by a written statement indicating the types of repairs needed. In the case of electronic devices, the request should describe conditions under which the instrument does not function properly, i.e. coldness, dampness, etc. if a “loaner” is needed, this should also be indicated. 6. Care of Tools Improperly maintained tools can be a source of annoyance, as well as being a safety hazard. Each employee is responsible for keeping his or her tools and equipment in good condition. To prevent loss of small equipment and tools, avoid laying them on the ground, on vehicles, or on equipment which might be moved. When not in use, carry them in scabbards and pouches. Repair or replace any driving tool that is burred or fractured on any part of the striking or driving face. Many surveyors have been injured by the “shrapnel” effect from gads and sledges which had ragged edges. The same is true for “bull points” or other tool which are driven. Crooked or warped handles can cause injury as well as mistitling and damage to the tool. Promptly replace such handles and those that are cracked or broken. Handles should be firmly secured in all cutting and driving tools. 7. Care of Theodolites and Total Stations §  Although the instruments are ruggedly built, careless or rough use and unnecessary exposure to the elements can seriously damage them. If handled reasonably, they will provide consistently good result with a minimum of downtime for repair or adjustment. Some general guidelines for the care of instruments are: §  Lifting – instruments should be removed from the case with both hands, gripping the micrometer knob standard and base on the older instruments. Newer instruments are equipped with a carrying handle; the other hand should support the base. One hand should continually support the instrument until the tribrach lock is engaged and the tripod fixing screw secured. §  Carrying Tripod - In most cases, the instrument should be removed and re-cased for transportation to a new point. If the point is nearby, the instrument should be carried in the vertical position (tripod legs pointing straight down). An instrument should never be “shouldered” or carried horizontally. §  Adjusting collimation – The collimation error of theodolites and total stations is determined by following the procedure outlined in the users’ manual. If the collimation error is found to be consistently in excess of ten seconds on the horizontal and twenty seconds on the vertical, the instrument should be adjusted. The collimation adjustment should be made in the field only by a specially trained individual. Otherwise, the instrument should be returned to an authorized repair shop. 8. Care of EDM Devices §  EDMs are designed, contracted and tested to withstand normal field conditions. They are however, precision instruments and should be handled with the same degree of care required for other types of precision survey equipment. §  Secure EDM in vehicles in padded compartments with substantial the downs so movement and jarring are minimized. Cushion with firm polyfoam or similar material. Do not use soft foam rubber. The instruments should be stored and transported in the position indicated on the case. §  Required maintenance of most EDMs is minimal. However, protection from the elements and routine external cleaning is necessary. §  NEVER point an EDM directly at the sun. The focused rays of the sun can damage sensitive internal parts. §  Protect EDMs from excessive heat. Heat can cause erratic readings and deterioration of components. Do not leave instruments in closed vehicles that are parked in the sun. Avoid rapid changing temperature, particularly from extreme cold to warm, which can cause condensation in the internal parts of the instruments. Condensation can normally be avoided by leaving the instrument in its carrying case for at least 10 minutes and then opening the case to allow any trapped moisture to evaporate. An instrument taken from a warm office or vehicle to an extremely cold operating environment may require some time to adjust itself. The same type of precautions should be taken to let the instrument cool off slowly. §  Although EDM instruments are water resistant and well shielded, keep them as dry as practicable. The case should be opened and the instrument allowed to dry in a warm dry room when not in sue. §  Frequent partial discharge and charge of batteries could cause the battery to lose its ability to hold power. Periodically, batteries should be discharged completely and then recharged overnight, or for the specified charge time. Effective usage of batteries will also decrease at low temperatures. An EDM in the tracking mode position will discharge the battery will also decrease at low temperatures. An EDM in the tracking mode position will discharge the battery quite rapidly, so it is important to be able to charge batteries to their maximum capacity. In general, one should follow the user’s manual instructions on how to maintain the batteries for top performance. If the batteries still fail to hold power, they should be re-celled or replaced. 9. Care of Tapes §  Routine care extends tape life. The following are basic guidelines for the care of tapes. §  Do not place a tape where it can be stepped on or run over, unless the tape is flat, taut, and fully supported on a smooth surface. Keep the tape straight when is used. When pulling a slack tape, a loop can develop into a kink and easily break the tape. Avoid pulling a tape around poles or other object, as a hard pull can stretch or break the tape. §  Do not wind tapes overly tight on their reels, as it can cause unwanted stresses and lead to stretching of the tape. §  After the day’s work, clean tapes that are soiled. In wet weather, dry before storing. Clean rusty tapes with fine steel wool and cleaning solvent or kerosene. Use soap and water when tape is dirty or muddy. To prevent rust after cleaning, oil lightly and then dry the tape. §  Avoid storing in damp places. 10. Care of Tribrachs Tribrachs are an integral part of the precision equipment and should be handled according. They should be transported in separate compartments or other containers to prevent damage to the base surface, bulls eye level, and optical plummet eye piece. Over tightening of the tripod fastener screw can put undue pressure on the leveling plate. 11. Care of Tripods A stable tripod is required for precision in measuring angles. A tripod should not have any loose joints or parts which might cause instability. Some suggestions for proper tripod care are: Maintain firm snugness in all metal fittings, but never tighten them to the point where they will unduly compress or injure the wood, strip threads or twist off bolts or screws. Tighten leg hinges only enough for each leg to just sustain its own weight when legs are spread out in their normal working position. Keep metal tripod shoes tight and free of dirt. Keep wooden parts of tripods well painted or varnished to reduce moisture absorption and swelling or drying out and shrinking. Replace top caps on tripods when not in use. 12. Care of Levels Review the previously stated guidelines for the care of instruments. These guidelines are also generally true for the proper care of pendulum levels. Additional guidelines are. Do not spin or bounce pendulum levels, as such movement can damage the compensator. Protect the level from dust. Dust or foreign matter inside the scope can cause the compensator’s damping device to hang-up. Frequently check the adjustment of the bull’s eye bubble. Adjust the bull’s eye to the center, not almost to the center. Make certain it is adjusted along the line of sight and transversely as well. Proper adjustment reduces the possibility of compensator hang up. To check for compensator hang up, slightly tap the telescope with a pencil or operate the fine movement screw jerkily to and fro. If the instrument has a push button release, use it, if the compensator is malfunctioning, send the instrument to an approved repair service for servicing. Do not attempt compensator repair in the field. 13. Care of Leveling Rods. Leveling rods should be maintained and checked as any other precision equipment. Accurate leveling is as dependent on the condition of the rods as on the condition of the levels. Reserve an old rod for rough work, such as measuring sewer inverts, mud levels, etc. The care requirements common to all types of rods are:- Protect from moisture, dirt dust and abrasion Clean graduated faces with a damp cloth and wipe dry. Touch graduated faces only when necessary and avoid laying the rod where the graduated face will come into contact with other tools, objects, matter, or materials where damage might result. Do not abuse a rod by placing it where it might fall, throwing, and dropping, dragging, or using it as a vaulting pole. Keep the metal shoe clean and avoid using it to scrape foreign matter off a bench or other survey points. If possible, leave a wet rod uncovered, unclosed, and extended until it is thoroughly dry. Store rods, either vertically (not leaning) or horizontally with at least three point support, in a dry place and in their protective cases. Periodically check all screws and hardware for snugness and operation Periodically check accuracy by extending the rod to its full length and checking its scale with an accurate tape. This should be done at the beginning of control level surveys. If the rod indicates a tendency to be “off”, it should be checked each time it is extended.

Steps in carrying out Triangulation work - How to do triangulation
	Triangulation work is carried out in following step. Reconaissance Erection of Signals & Towers Measurement of Horizontal Angles Astronomical Observations Necessary to Determine the True Meridian and the Absolute Positions of the Stations Measurement of Baseline Adjustment of observed Angles Computations of Legths of each side of each  Computations of the Latitude and Longitude of ST 1. Reconaissance: In geodetic Surveying, reconaissance consists of: (See also: Reconaissance in Transportation & Highway Engineering ) Examination of the country to be surveyed. Selection of most favorable sides for base lines Selection of suitable positions of  station Determination of indivisibility of station 2. Selection of Station: The selection of station is based upon the following consideration. The stations should be clearly visible from each other. For this purpose highest commanding positions such as top of hills or mountains is selected. They should form well shaped triangles They should be easily accessible They should be useful for detail survey Thy should be so fixed that the length of sight is not too short or too long
3. Intervisibility and Hights of Stations: For indivisibility of two stations they should be fixed on highest available ground. Such as mountain peaks rides or top of hills when the distance b/t the two stations is great and the difference in elevation b/t them is small then it is necessary to raise both the instrument and signal to overcome the curvature of the earth and to clear all the intervening obstruction. The height of both the instrument and signal above the ground depends upon. Distance between the stations Relative elevations of stations The profile of intervening ground 3. 1. Distance between stations: If the intervening ground is free any obstruction, the distance of a visible horizon form a station of known elves above datum as well as the elves of the signal while may be just visible at a given distance can be determine from the formula.      Where H = ht. of station above a datum  D = Dist from the station to point of tangent R = mean radius of earth M = co-efficient of refraction (0.07 for sight over land and 0.08 for sights over water) D1 and R being expressed in same units. Alternatively, if ‘h’ is in meter and D1 is in kilometer then H (m) = 0.0673 D12 (km) ==> (A) Or H (ft) = 0.574 D1 (miles) ==> (B) D1 and D2 can be determined and dist b/t two stations will be (D1+ D2) 3. 2. Relative elevations of stations: A and B are the two stations D = dist b/t A and B in km Ha = known elev of ‘A’ above a datum H = required elev of ‘B’ above a datum D1 = distance (km) of ‘A’ from pt of tangency (p) D2 = distance (km) of ‘B’ Dist D1 can be calculated. Hence the required elev, h = 0.0673 D2 Ha = 0.0673 D12   or       h = 0.0574 D22 (miles)   Or  Now D2 = D - D1 Height or signal / Tower/ scaffold a B = Elev of datum + h - R.L of st B elev of line sight NOTE: The line of sight should not be near the surface of ground at pt of tangency on account of strata of disturbed air and should be kept at least 2m (61) above the ground permeably 3m (1D) and this allowance (clearance) should be made in deterring the heights of stations. 3. 3. Profile of intervening ground: If the peaks in the intervening ground are likely to obstruct, the line of sight, their elevations and locations must be determined. Procedure: The elevation of line of sights at the respective points can be computed and the results compared with the ground elevation at those points to determine weather the line of sight clears all the intervening obstruction.

Lesson Note On Hydrographic Surveying

Hydrographic Surveying
	Definition: It is the branch of surveying which deals with any body of still or running water such as a lake, harbor, stream or river. Hydrographic surveys are used to define shore line and under water features. Objects of Hydrographic Surveying: Hydrographic surveying are carried out for one or more of the following activities. Measurement of tides for sea coast work E.g. construction of sea defense works, harbors etc, for the establishment of leveling datam and for reducing sounding. Determination of bed depth, by soundings For navigation Location of rocks, sand bars, navigation light. Fro location of under water works volumes of under water excavation etc. In connection with irrigation and land drainage schemes.
Determination of direction of current in connection with The location of sewer any pipe or channel that carry waste water out falls.   Determination of area subject to silt and seour the eating of the place. Fornication purposes. Measuremenment of quantity of water and flow of water in connection of water schemes, Power scheme and flood controls. Why we need Hydrographic Surveys - Uses & Applications of Hydrographic Survey Offshore engineering and the shipping industry have continued to expand. Drilling rigs (extracting oil, gas etc from deep sea) locating up to 125miles offshore, search for resources particularly oil and gas. Offshore islands are constructed of dredged material (to bring material form some where and dump there) to support marine structure. Harbor depth up to 80 is required to accommodate larger ships and tankers. Containerization has become an efficient and preferred method of cargo handling. The demand for recreational transportation ranges form large pleasure cruise ships to small sail bonds. Cruise ships to small sail bonds. Hydrographic surveys are made to a quire and present data on oceans, lakes and harbors. It comprises all surveys made for The determination of shore lines, soundings (measurement of depth below the water level) characteristics of bottoms, areas subjected to Suring and silting, depth available for navigation and velocity as well as characteristics of flow of water. The location of lights rocks sand balls, buoys ( anything that floats on the surface of water) Establishing Horizontal and Vertical Controls (Click Here) The first step in making a hydrographic survey is to control both horizontal and vertical. Horizontal Controls: In an extensive survey, the primary horizontal control is established primarily by running theodolite and tape traverse before the triangulation station. Tthe traverse lines being run to following the shore lines approximately. In survey of less extent the primary horizontal control only is required and is established by running a theodolite and tape traverse sufficiently close to shore line. For rough work, the control may be established by running a theodolite and staid traverse or plane table trader. Vertical Controls: These are based upon a series of bench marks established near the shore line by spirit leveling and these serve for setting and checking tide gages etc to which the sounding are referred. River Surveying The survey of the shore line of a river is made by running a theologize and tape traverse on a shore at a convenient distance form the edge of the water. If the river is narrow, a single theologize and tape traverse is on one bank and both banks. Located by staid or plane table methods. Sounding Surveying The measurements of depths below the water surface is called Sounding. The object of making soundings is to determine the configuration of the bottom of the body of water. This is done by measuring form the boat, the depth of water at various points

Units of Conversion

Units of Conversion

Length:

1 inch= 2.54 cm
1ft= 30.48 cm
     = 0.3048m
     = 3.281 ft

1m = 3.281 ft
1mile= 1.609km
1 naut mile= 1.852 km

Area:

1 Are= 100sq.m
          = 1 Gunta

1 Gunta= 33’X33’
1 acre = 43560 ft2
           = 4047 m2
           =0.4047 ha
1ha     = 10000m2
           = 100 areas
           = 2.471

Volume:

1Cu.ft= 28.32 lit
1 imp-gal = 4.546 lit
1m3= 35.315 Cu.ft
        = 1000 lit
1ha.cm = 100m3

Flow Rate:

1 cumec = 35.31 cusec
1m3 /s = 35.41 Cu.ft /s

Pressure :

1 atm= 1 bar
         = 1 kg/cm2
         = 14.7 psi
         =30 inch of Hg
         = 76 cm of Hg

Weight:

1kg = 2.2 lbs
1lbs= 453.6gms

1 carat= 200 mg

1 km2= 100 ha
          = 247 acres
     
1mile2 = 640 acres
            = 259 ha
            = 2.59km2

Power:

1 H.P = 74
          = 0.746 K.W

1 K.W. = 1000 watt
             = 1.31 H.P

Lesson Note On Programming Languages

Programming Languages

Two types of computer languages are used for programming, namely Low Level Languages and High Level Languages. Low Level Languages are further classified as Machine Languages and Assembly Language. High Level Languages are Fortran, Cobol, C, C++, Pascal, Java, etc

Low Level Languages:

Machine Language:

The lowest form of computer language is Machine Language.  Computer CPU can understand only instructions, written using pattern of 0s and 1s i.e. binary language. Hence, in machine language, instructions are formed with different combinations of the bits 0 and 1. For example, 001010110011 could represent an instruction in machine language. The instruction is followed by the data, if needed, in binary form. CPU of every computer (Microprocessor) is capable of executing a particular set of instruction in binary form. This set contains instructions for arithmetic operations, control, input and output operations. The programs written in machine language are called Object Programs. Coding the program in binary form is very tedious. Moreover, the bit patterns for every instruction in a set of about millions of such patterns are difficult to remember. Therefore, a symbiotic language called as Assembly Language was developed.

Assembly Language:

Assembly language consists of symbiotic words called mnemonics and it was extensively used during 1950. Symbolic instruction codes like ADD, SUB, MULT, DIV, IN, OUT etc. are used for operations of addition, subtraction, multiplication, division, input, and output respectively on the data. A set of such instruction codes were put together to form a program and store in memory, means were provided to translate these codes in to their machine language counter parts. The translated program is then directly executed. The assembly language instruction set is different for different microprocessors.

High Level Language:

It is easier to write program in Higher Level Language (HLL) than Assembly Language. Moreover, a program written in HLL can be used on any computer irrespective of the type of microprocessor and HW in computer, provided it has a compiler for the HLL used for programming.

Advantages of HLL Programming are:

1. Easier to learn as compared to assembly languages.
2. Most of the instructions are as like simple English.
3. Better documentation is provided for HLL.
4. The executions do not depend on type of HW in computer.

Some of the popular HLL are BASIC, FORTRAN, COBOL, PASCAL, C, etc. Every HLL has a vocabulary of specific words (commands) and set of rules to use these words called syntax. The set of commands include instructions for various operations like arithmetic and logic operations on the data, input and output and control statements. However, computer needs special means to convert a program written in HLL to machine language. These translators are called interpreters or compilers.

Lesson Note On Types of Computer Software

Types of Software

Software is Mainly Classified as:

1. System Software and Operating Systems
2. Application Programs
3. General Purpose Packages

System Software and Operating Systems:

System software includes programs that simplify use of computers, provide man machine communication and control & drive all input/output devices interfaced to a Computer. The type and utilities depend on the type of computer. However, most of them have system programs like monitor, operating system, editor etc.

BIOS (Monitor):

BIOS are a program that is stored in ROM and perform basic functions required in a microcomputer. These functions mainly include:

i) Power ON self Test which tests error free working of RAM, all I/O devices and reports accordingly.

ii) Managing the control devices.

iii) Control execution of program.

Operating System:

Computers need a set of program called Operating System to keep it working. These programs may not be used for a specific problem execution but they enable the computer to do all the different jobs in proper order and at the required time. For example, they keep track of the priority of different jobs and load the jobs in to the CPU for execution in correct sequence. OS also include programs, called utilities, which are useful to maintain day to day activities of the computer system like Copy, delete, sort, save, rename, print a file etc.

The Functions of the Operating System Include:

1. Scheduling and loading of programs or subprograms and continue the job processing sequence.

2. Control hardware resources such as Input/ Output devices, Secondary storage Devices etc.

3. Protect Hardware, Software form improper use.

4. Communication with user through commands and response.

5. File management and software management.

6. Memory management.

Operating system is a most powerful and important software in a computer. The HW along with OS and other SW forms a complete computer system.

The Most Popular Operating  Systems are

i) DOS
ii) WINDOS
iii) UNIX/LINUX

Application Program:

These are program written for a specific job to meet the requirements of a particular user. For example program for pay billing in an organization, statistical data analysis, admissions at MAU are all application program. These are generally written in different high level computer languages and then complied to translate them in an executable from.

General Purpose Packages:

A general purpose package of software is collection of generalized application programs and utilities for a particular type of job so that it can be easily usable by nonprograming persons. Because of which they are called as user friendly programs. With ease of use in mind, selection of commands through menus is frequently incorporated in the design of these general purpose packages. These menus present options which enable the user to select an appropriate course of action, exactly similar to presenting menu to a customer in a restaurant. The users do not need to remember what to do next. Package programs are available for applications which are common to many users. Some example of popular software package are WordStar, MS-Word, Word Prefect for word processing, dBase, Fox Pro for database management, LOTUS, MS- EXCEL for spreadsheet.

Advantages of these Packages Include:

1. The users himself need not write programs in HIL.
2. Easy to use and user friendly.
3. Small application programs may be developed by an user as per requirement using a set of commands available in these package.
4. Documentation on how to use and maintain the software is provided by the vendor.

Some Instruments for Setting out Right Angles

Instruments for Setting out Right Angles

Cross staff:

The cross staff is used for

a) Finding out foot of the perpendicular from a given point to a line
b) Setting right angle at a given point on a line

There are three forms of cross staff

1. Open cross staff
2. The French and
3. The Adjustable
4. Optional Square
5. Prism square, the first one is commonly use.

1. Open Cross Staff:

It is a simple. It consists of two parts: - 1) the head; 2) the leg. The common type of cross staff consists of 4 metal arms with vertical slits for sighting through.

The head is fixed to the top of an iron stand about 1 .2 to 1.5 m long this is driven in to the ground.

For setting perpendiculars lines, one pair of opposite arms is aligned with the chain line. It is specially used for setting off and marking contour lines.

To find the foot of perpendicular from a given point to a given lines:

To take offset, the cross staff is held vertically on chain where the offset is likely to occur, and turn until one pair of opposite slits directed to arranging rod at the forward end of the chain line, the offset is taken is bisected. If not the cross staff is moved forward or back word the chain line until the line of sight through the pair of slits at right angle the chain lines, does bisect the point.

In setting out a right angle at point on the chain line:

The cross staff is held vertically over the given point on the chain and turn until the ranging road at either end of the chain line is bisected the line of slight through 1 pair of the opposite slits. Then the line through the other pair of slits which is at right angles to the chain line through the other pair of slits which is at right angles to the chain line. Line may be marked by a ranging rod at inconvenient point on the sighted.

2. French Cross Staff:

The octagonal form cross staff is the French cross staff. It consists of an octagonal brass tube with slits on all eight sides. If has an alternate vertical slit and an opposite vertical window with a vertical horse hair or affine wire on each of the four sides. These are used for setting our right angles. On the other side are vertical slits, which are at 45 degree to those previously mentioned, for setting out angles of 45 degree.

The base carries a socket so that it may be fitted on the pointed staff when the instrument is to be used. The sight being too close (only 8 cm apart) it is inferior to the open type.

3. Adjustable Cross Staff:

It consists of a brass cylindrical tube about 8 cm in diameter and 1 cm in deep, and is divided in the centre. The upper cylinder can be rotated relatively to the lower one by a circular rack and pinion arrangement actuated by screw. Both are provided with sighting slits. The lower part is graduated to degrees and sub divisions, while the upper one carries a vernier. Thus it may be use for setting out angles of any magnitude. It has a magnetic compass at the top, which may serve to take the bearing of the line.

4. Optional Square:

An optional square is an compact hand instrument used in setting out right angles with greater accuracy than a cross staff. It consists of a circular box about 5 cm in diameter and  1.25 cm deep in which two mirrors are fitted at right angles to the plane of instruments . The mirror ‘h’ called the horizontal glass which is half silvered and half uncovered. The mirror ‘I’ is known as index glass is known as wholly silvered. There are three openings on the side of box at e, b and ,c. the opening e is pin whole for eye , b is small rectangular slot placed opposite to pin hole and c is large rectangular slot placed at right angle to line joining e & b

The surveyor simply turns the optical square upside down which throws the aperture for the object on that side.

5. Prism Square:

It is a modern instrument and is a very use full for setting out right angles. It is based on the same principles as the optical square and is used in same manner. It requires no adjustment, since the angle between reflecting surface of the prism (45 degree) is fixed. It is unaffected by dust & can be used in poor light. For taking offset to an object the observer holds the instrument in his hand & slights directly over the prism at ringing of station.