SVY2301 / E4006 AUTOMATED SURVEYING SYSTEMS

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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 days fieldwork.
• 2. Recorded data should be secure against
  accidental loss.
• accidental keystrokes
• memory 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

1. 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 days operation.
• The data recording facility should be capable of
  being interfaced with all electronic surveying
  equipment.
• 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.
• The display should be visible in all daylight
  conditions
• 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

• logical, easily understood, flexible and
  efficient.
• give alphanumeric prompts for information when in
  the data recording mode.
• 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.
• enable the efficient transfer of recorded data to
  a computer
• 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 00000 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 gt 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 ROs 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 ( DR )
• Necessary when 00000 has been set to the RO
• Collimation ( Coll )
• If known, the horizontal collimation correction
  may be applied
• Angular offset to targets ie trees ( a )
• 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

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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 Hzc
• RL RLo HI V HT
•  
• and where
• V HD Cot ZDc (c r) or
• V HD Cot ZDc

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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 dont
• 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 interpolation

101 contour
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Creation of DTM

• Contours generated after DTM formed
• formed by interpolation

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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