SVY2301 / E4006 AUTOMATED SURVEYING SYSTEMS Revision

SVY2301 / E4006AUTOMATED SURVEYING

SYSTEMS

Revision

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

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

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


Measurement – Single Axis Compensation

• Corrects for the tilt in the vertical axis.


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.

•


Measurement – Dual Axis Compensation


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


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


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


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

SVY2301/E4006

Electronic Data Recording

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.

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;

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;

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.

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


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


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.


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.


11. The use of the data recording facility keyboard should not disturb the functions or accuracy of electronic surveying equipment

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.

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.

SVY2301/E4006

Field Coding Systems

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

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

The Functions of a Fieldbook Fieldbooks record a variety of

information including:• Registration information• Measurement information• Descriptive information• Graphical information

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.


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

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


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.


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


Simple Mnemonic (Alpha) System

A string code is normally used with the feature code to distinguish graphical features and allow connectivity.


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.


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


Comprehensive Feature Codes


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.


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

SVY2301/E4006Automated Surveying Systems

Field Operations and Techniques

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

Preparation and Planning (Field)

• Search area for survey control marks

• Walk the area

• Prepare a sketch

• Locate survey control stations

Control Establishment• Horizontal

– Ensure control is closed– Determine number of angles & distances

to be observed to achieve desired accuracy

• Vertical– Determine suitable levelling method

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

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

Topography

• Purpose is to accurately describe the topography in the area

• random spot heights• changes of grade banks, gullies• ensure breaklines are utilised

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

Fieldbook Recording

• Instrument heights• String numbers• Changes in prism heights• Errors in coding• Other miscellaneous graphical

information

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

Processing and Reduction

• Data Transfer• Reformatting• Processing• Editing and Computations• Creation of DTM and Contours• Volumes

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

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

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

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

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

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

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

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–

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

Editing and Computations

• Correction of processing errors

• Editing of Reduced Data

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

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

Creation of DTMCross-Section Modeller• based on the traditional

engineering method of cross-sections of the surface at fixed intervals

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

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.

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

Creation of DTMPoints Modeller - Triangulation Points Only


Also showing line of gully


Triangulation

Note triangles formed across gully


Contours interpolated between points defining triangles


Necessary to locate more points along the gully in order to force the correct triangle formation

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.


Points and lines defined



Triangulation

Note line of gully forms the triangle sides



Contours interpolated between points defining triangles


Contours from points only


Contours from points and lines


Comparison of the two digital terrain models

Creation of DTM

• DTM editing– Edit or delete triangles– insert breaklines– eliminate duplicate points– eliminate crossing breaklines

Creation of DTM

• Contours generated after DTM formed– formed by interpolationRL 102.01

RL 100.01 RL 100.50

RL 101.50

101 contour

Creation of DTM

• Contours generated after DTM formed– formed by interpolationRL 102.01

RL 100.01 RL 100.50

RL 101.50

DTM Creation

• Contours– straight or smoothed– take care in using smoothing

algorithms

Volume Calculations

• Cross-sections

• triangles or prismoids

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

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

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

Testing Software

• Is the software correct?• Should test using known data

under a variety of configurations• Process is part of a quality

assurance system

Documents

SVY2301 / E4006 AUTOMATED SURVEYING SYSTEMS Revision