svy2301 / e4006 automated surveying systems revision
TRANSCRIPT
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SVY2301 / E4006AUTOMATED SURVEYING
SYSTEMS
Revision
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Developments in Total Stations • Some of these developments include:
– Development of Electronic Angle Measurement
– Axis compensation– Motorisation and robotics– Developments in onboard software– Storage media and memory management– Developments in onboard software
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Developments in Electronic Angle Measurement
• Traditional system of angle measurement required the use of micrometers to read and interpolate the inscribed glass plate of theodolite.
• Electronic Angle Measurement is now generally completed by one of two techniques:– Incremental Measurement, or– Absolute Measurement
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Developments in Electronic Angle
Measurement – Axis Compensation
• automatic axis compensation corrects for errors in tilt in the horizontal and vertical axes.
• Conventional systems used a plate bubble for the horizontal levelling and a pendulum sensor for the vertical axis compensator.
• Electronic tilt sensors are usually liquid type compensation systems with either:– Magnetic detection or– Photodiode detection
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Developments in Electronic Angle
Measurement – Single Axis Compensation
• Corrects for the tilt in the vertical axis.
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Developments in Electronic Angle
Measurement – Dual Axis Compensation
• Dual Axis compensation corrects for– the inclination of the vertical axis in the
direction of pointing, and– in the direction of the trunion axis.
• axis produces errors in horizontal angles particularly in steep vertical sights.
•
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Developments in Electronic Angle
Measurement – Dual Axis Compensation
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Developments in Electronic Angle
Measurement – Motorised Total Stations
• Motorised systems are characterised by:– Horizontal and vertical servo motor– Motors operate at high (course) and slow
(fine) speeds– No tangent screws required– Very good for setout of points– Price approx $12-$16K
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Developments in Electronic Angle
Measurement – Self Tracking Total Station • The self tracking systems allow the automatic
tracking of a prism. – Basic motorised system plus– Laser tracking system parallel to lens system– Track at high speeds– Automatic search routine when lock is lost– Focus not required– Faster and more accurate then human pointing– Can operate at night or low light conditions– Inbuilt communications to indicate that system is reading– Approx cost $17-$25K
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Developments in Electronic Angle
Measurement – Robotic System
• Robotic system is the next step up from the self tracking system and includes all the features of a self tracking system plus:– Robotic software– Telemetry link– Remote control unit with key pad entry– Requires only one person– Surveyor may require assistance when
placing pegs– Approx cost $30 -$40K
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Developments in Electronic Angle
Measurement – Reflectorless Total Stations
• Developed to allow measurement to virtually any surface without the need to utilise a prism.
• Charcterised by:– Measure approx 80m w/o prism– Measure buildings and structures with
one person eg tunnel profiling– +/- 3mm– limited by surface reflectance and
light conditions
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SVY2301/E4006
Electronic Data Recording
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Objectives • explain in detail the purpose of an electronic data
recording facility;• describe the components of an electronic data
recording facility;• list and describe the essential features of an
electronic data recording facility;• explain the meaning of typical specifications for a
data recorder, given an appropriate specification sheet;
• compare the features of one data recording with those of other facilities; and
• describe the features and operation of one data recording facility the student has studied.
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Purpose of an Electronic Data Recording • to receive digital data from electronic
surveying equipment and store it in a secure and reliable storage medium.
• to manually record all of the information normally recorded in a fieldbook;
• to transfer stored digital data to a computer, an electronic surveying instrument or to a back-up storage device;
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Purpose of an Electronic Data Recording (cont)• to transfer stored data, either
formatted or unformatted, to a printer to obtain a hard copy of the data;
• to edit data in a stored data file whilst maintaining the integrity of the data;
• to control the operations of electronic surveying equipment by using the keyboard of the data recorder or by a program running in the data recorder;
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Purpose of an Electronic Data Recording (cont)• to control data recording
processes from the keyboard of an electronic surveying instrument; and
• to complete all normal tasks efficiently whilst still allowing the user a degree of flexibility in the methods they use.
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Features of an Electronic Data Recording Facility Essential Hardware Features
1. Storage Capacity - one day’s fieldwork.
2.Recorded data should be secure against accidental loss.accidental keystrokesmemory unable to be cleared until the data has been transmitted to another device
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Features of an Electronic Data Recording Facility Essential Hardware Features
3.Recorded data should be secure against accidental power failure.back-up battery system. the integrity of the data must remain intact
4. The ROM and RAM memories should be protected against interference from radio transmissions and other electromagnetic sources
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Features of an Electronic Data Recording Facility Essential Hardware Features
5. The power supply should be sufficient for at least one full day’s operation.
6. The data recording facility should be capable of being interfaced with all electronic surveying equipment.
7. The data recording facility should be capable of being interfaced with computing equipment.
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Features of an Electronic Data Recording Facility Essential Hardware Features
8. The data recording facility should have a full alphanumeric display.
9. The display should be visible in all daylight conditions
10.The recording facility should allow data to be recorded manually via a keyboard.
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Features of an Electronic Data Recording Facility Essential Hardware Features
11. The use of the data recording facility keyboard should not disturb the functions or accuracy of electronic surveying equipment
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Features of an Electronic Data Recording Facility Essential Software Features
1. logical, easily understood, flexible and efficient.
2. give alphanumeric prompts for information when in the data recording mode.
3. enable non-measurement information to be recorded.
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Features of an Electronic Data Recording Facility Essential Software Features
4. enable the efficient transfer of digital data from electronic surveying equipment.
5. enable the efficient transfer of recorded data to a computer
6. enable measured data to be recorded without any deterioration in accuracy.
7. enable recorded measurements to be tagged.
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SVY2301/E4006
Field Coding Systems
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Objectives • describe in detail the types of information recorded
in a field book;
• describe in detail, using examples where necessary, how these types of information can be coded in the field;
• explain the different field coding systems currently utilised; and
• describe the advantages and disadvantages of each coding system
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Introduction• digital surveying equipment has eliminated the
need to record field measurements in a fieldbook• measurements are recorded in an electronic data
recorder at the touch of a button• the fieldbook becomes a purely descriptive or
diagrammatic representation of the survey• the measurements recorded in a data recorder
must be tagged in some way to enable them to be identified with the points that were surveyed
• Generally the method used to tag measurements is known as a field coding system
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The Functions of a Fieldbook Fieldbooks record a variety of
information including:• Registration information• Measurement information• Descriptive information• Graphical information
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Electronic Fieldbook Field Coding System
Three field (feature) coding systems are detailed to illustrate the most commonly utilised systems.
• simple numeric system,• simple mnemonic (alpha) system, and• comprehensive numeric system.
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Electronic Fieldbook Field Coding System
Simple Numeric System
• consisted of two or three digit numeric codes which were related to a corresponding feature
• the three digit code tended to evolve as the defacto standard for the numeric coding system
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Electronic Fieldbook
Field Coding System
Simple Numeric System
• Numeric codes are normally divided up into groups
• A string code is normally used to distinguish graphical features and allow connectivity
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Electronic Fieldbook Field Coding System
Simple Numeric System• The advantages of this coding system are:
– simple; - codes entered quickly;
– compatible with nearly all total stations; and
– it is very efficient.• The disadvantages are:
– codes are not easily recognisable;
– often require a code sheet to remember; and
– the system does not allow for very complex graphical coding.
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Electronic Fieldbook Field Coding System
Simple Mnemonic (Alpha) System
• precise alphanumeric feature coding method that can save typing time in the field
• Only two or three characters are needed to describe the feature compared with a full description
• utilized by the computer software to plot symbols or write descriptions on the feature points
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Electronic Fieldbook Field Coding System
Simple Mnemonic (Alpha) System
A string code is normally used with the feature code to distinguish graphical features and allow connectivity.
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Electronic Fieldbook Field Coding System
Simple Mnemonic (Alpha) System• The advantages with this system are:
– simple; - codes are easy to remember; and
– very efficient.
• The disadvantages are:
– system does not allow for more complex graphical coding;
– not all systems can use alpha codes; and– may be more time consuming to enter codes
if instrument does not have an alpha keyboard.
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Electronic Fieldbook Field Coding System
Comprehensive Feature Codes
• The Australian Survey Office (ASO) Feature Coding System
• allows the surveyor to code each detail point under all four categories, i.e. feature description, feature type or material, vertical location and horizontal location
• a main code/sub-code type, with each of the codes being numeric
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Electronic Fieldbook Field Coding System
Comprehensive Feature Codes
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Electronic Fieldbook Field Coding System
Comprehensive Feature Codes• The advantages of this system of
coding are:
– it is very comprehensive and allows for accurate description of features; and
– there is minimal additional drafting in the office.
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Electronic Fieldbook Field Coding System
Comprehensive Feature Codes• The disadvantages are:
– it is slow and complex in the field;– it always requires the list of codes
in the field; and– the system is not particularly cost
effective
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SVY2301/E4006Automated Surveying Systems
Field Operations and Techniques
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Preparation and Planning (Office)• Understand the purpose of the survey
• Gather relevant maps/plans of the area
• Survey Control Search
• Determine survey methodology based on desired accuracy and site topography
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Preparation and Planning (Field)
• Search area for survey control marks
• Walk the area
• Prepare a sketch
• Locate survey control stations
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Control Establishment• Horizontal
– Ensure control is closed– Determine number of angles & distances
to be observed to achieve desired accuracy
• Vertical– Determine suitable levelling method
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Field Pickup
• set 0°00’00” to the RO, LISCAD will orientate the survey during the reduction
• radiate to the required points• Maximum sight distance depends
on required accuracy• Always check back to control or
known points every 20 to 30 shots
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Feature Location
• Dependent on the purpose of the survey
• May include– Trees > 0.15m diameter– structures ie buildings– fences– services - both underground and
aboveground– topography
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Topography
• Purpose is to accurately describe the topography in the area
• random spot heights• changes of grade banks, gullies• ensure breaklines are utilised
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Operation of the Survey
• Utilise sketch to assist in completing the designated area
• Need to extend the area to ensure the contours are representative
• Strings may be run successively or by using a cross-section method
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Fieldbook Recording
• Instrument heights• String numbers• Changes in prism heights• Errors in coding• Other miscellaneous graphical
information
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Checks
• Always undertake checks• Use two RO points if possible so that
you can check your coordinates and orientation
• Check back to your RO’s every 20-30 shots
• If you are traversing, pick up the same point from another station as a quality check
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Processing and Reduction
• Data Transfer• Reformatting• Processing• Editing and Computations• Creation of DTM and Contours• Volumes
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Transfer of Data• Communication parameters
– baud rate ( speed - bits per second)• E.g. 9600bits/sec
– Communications port• E.g. COM 1, COM 2
– stop bits• Usually 1 or 2
– data bits (word length)• Usually set to eight
– Parity (error checking)• Usually set to none
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Data Transfer
• Because it contains original field observations the downloaded file is referred to as a RAW file
• Always make a backup copy of the raw file before making any amendments
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Reformatting Data File
• Change from proprietary to internal format Eg from Leica to Liscad Field file
• Identifies any anomalous data• Internal format easier to read and
to edit than the raw file
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ProcessingInitial Editing
– Made to field file to correct errors normally recorded in a field book
– Error examples include• Correct prism heights• Correct feature codes• Correct string numbers• Correct or place instrument coordinates
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Processing - Reduction of Data Raw Distances
• Reduction of raw distances• EDM constants – Scale factor (S) &
Instrument/Prism constant (C)• Atmospherics – field and standard pressure &
temperature used in a formula to produce a PPM correction (C2)
• Arc to chord – curved distance to straight line chord (Arc)
• Slope - slope distance reduced to the horizontal using the vertical angle (ZD)
• Distance Offset Correction – (Offset) Corrected Slope Distance (SDc) ={[(SD S) + C] + C2} – Arc
Horizontal Distance = (SDc SinZD) + Offset
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Processing - Reduction of Data Horizontal Angles
– Rotation ( R )• Necessary when 0°00’00” has been set to the RO
– Collimation ( Coll )• If known, the horizontal collimation correction may be
applied
– Angular offset to targets ie trees ( )The angular offset correction is computed by the
amount of offset distance and the horizontal distance.
For a horizontal distance of 120.56m and an offset of 0.32m the correction may be computed by:
True Angle
Offset
Tree
"07'09056.120
32.0tantan
arcHD
offsetarc
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Processing - Reduction of Data Vertical Angles
• Vertical Angles– Collimation
• Essential for surveyors to know the vertical collimation of their instrument because all pickup is typically done on one face ONLY and any collimation error will be uncorrected
• The corrected vertical angle (ZDc) can be calculated by
ZDc = ZD + coll
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Processing Computation of E, N and RL
• Computation of E, N and RL– The coordinates of the individual points may
now be calculated by the following formulas:
E = Eo + HD sin Hzc N = No + HD cos
HzcRL = RLo + HI + V – HT
and whereV = HD Cot ZDc + (c – r) or V = HD Cot ZDc +
HD2
R----------- 0.5 k–
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Processing Decoding of Feature Codes and Strings • Decoding of Strings
– Firstly sort file by feature code and string– Check all codes match and warn if they don’t– if a point code, program will draw symbol
referenced in code table• Maybe scale symbol as well
– Group all feature codes and strings together, program draws string with attributes in code table
• Line type, colour, layer etc• May also close string if program allows for an
appropriate code
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Editing and Computations
• Correction of processing errors
• Editing of Reduced Data
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Editing and Computations• Computations after reduction of the
field file– computations of bearing and distances,
and– area calculations
• Computations before reduction of the field file– horizontal adjustments,
– vertical adjustments
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Creation of DTM
• DTM formed by modelling contourable points and lines
• Three main types of DTM modellers– Cross sections or strings only– Points only– Points and Lines (Liscad) and most
common
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Creation of DTMCross-Section Modeller• based on the traditional
engineering method of cross-sections of the surface at fixed intervals
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Creation of DTMPoints Modeller• the surface is assumed to be
smooth between each point and its neighbours
• A process called ‘triangulation’ is used to define the surface between the points modelled in a computer
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Creation of DTMPoints Modeller - Triangulation• triangles are formed by joining each
point to its neighbouring points by straight lines.
• many different ways of forming triangles with a given set of points– each triangulation algorithm operates
using certain but often different criteria. • Generally the most equi-angular
triangles are selected.
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Creation of DTMPoints Modeller - Triangulation• Each triangular plate is regarded as
being representative of the surface between the three points.
• This form of modelling is often called TIN (Triangular Irregular Network) – based on the use of irregularly spaced
points
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Creation of DTMPoints Modeller - Triangulation Points Only
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Creation of DTMPoints Modeller - Triangulation Points Only
Also showing line of gully
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Creation of DTMPoints Modeller - Triangulation Points Only
Triangulation
Note triangles formed across gully
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Creation of DTMPoints Modeller - Triangulation Points Only
Contours interpolated between points defining triangles
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Creation of DTMPoints Modeller - Triangulation Points Only
Necessary to locate more points along the gully in order to force the correct triangle formation
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Creation of DTMString & Points Modeller
• model is represented by string lines and points.
• string lines are used to define changes of grade in the surface - referred to as breaklines or barrier strings– gullies, banks, ridge lines, cliffs etc.; and
– the top of an embankment, the toe of an embankment, the top of a kerb, the invert of a kerb, the crown of a road, etc.
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Creation of DTMString & Points Modeller
Points and lines defined
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Creation of DTMString & Points Modeller
Points and lines defined
Triangulation
Note line of gully forms the triangle sides
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Creation of DTMString & Points Modeller
Points and lines defined
Contours interpolated between points defining triangles
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Creation of DTMString & Points Modeller
Contours from points only
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Creation of DTMString & Points Modeller
Contours from points and lines
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Creation of DTMString & Points Modeller
Comparison of the two digital terrain models
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Creation of DTM
• DTM editing– Edit or delete triangles– insert breaklines– eliminate duplicate points– eliminate crossing breaklines
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Creation of DTM
• Contours generated after DTM formed– formed by interpolationRL 102.01
RL 100.01 RL 100.50
RL 101.50
101 contour
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Creation of DTM
• Contours generated after DTM formed– formed by interpolationRL 102.01
RL 100.01 RL 100.50
RL 101.50
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DTM Creation
• Contours– straight or smoothed– take care in using smoothing
algorithms
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Volume Calculations
• Cross-sections
• triangles or prismoids
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Volume Calculations
• Cross-sections– traditional formulae are used to
calculate volumes from cross-sections generated by the computer from the surface model.
– the cross-sections may be from one surface to another or from a surface down to a base level or datum height
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Volume Calculations
• triangles or prismoids– the area of each triangle is
calculated and is multiplied by the average height of the triangle above the datum plane.
– the total volume is given by the sum of all of the triangular prism volumes
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Volume Calculations
• triangles or prismoids (cont)– to calculate the volume between two
surfaces • The volume between each of the
surfaces and a datum level is calculated first. Then the required volume is the difference between those two volumes
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Testing Software
• Is the software correct?• Should test using known data
under a variety of configurations• Process is part of a quality
assurance system