Impact of Coordinate Collection Technology on Rural ...eprints.qut.edu.au/3950/2/3950b.pdf · Surveying in Queensland Robert Webb Seminar presentation for partial fulfilment towards

(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 1

Impact of Coordinate Collection Technology on

Rural Cadastral Surveying in Queensland

Robert WebbRobert Webb

Seminar presentation for partial fulfilment towards the award of

Master of Applied Science (Research)Master of Applied Science (Research)Master of Applied Science (Research)


Overview• Background• Introduction and Purpose• Why GPS is being considered for Cadastral

Survey Applications• Problems in Coordinate Descriptions• Routes for Establishing Traceability of GPS

measurements• Concept of Local Controlled Areas (LCA)• Measurement Based Multi Purpose Cadastre• Conclusions


Background• In the Australian Torrens title registration

system, the indefeasibility of title to land is guaranteed by the government.

• Such a guarantee is only meaningful if the boundaries of land are identifiable beyond any reasonable doubt.

• The process of determining and marking the boundaries of land for statutory purposes is broadly understood as Cadastral Surveying.


Background (continued) • Cadastral surveys have been performed by

Surveyors with the aid of an assortment of survey equipment such as: survey tapes, theodolites, electronic distance measuring (EDM) devices and more recently the potential of Differential Global Positioning System (DGPS).

• The equipment coupled with sound survey methods and professional judgement is used to provide for the determination of parcel boundaries.


Introduction• Most survey legislation requires

measurements of length to be traceable to the national primary standard of length through approved calibration methods.

• The National Measurement Act 1960 (Australia) stipulates that measurements are required to be legally traceable legally traceable if they are likely to form the basis for litigation.

• Currently in Australia, there is no acceptable means for establishing the legal traceability of GPS measurements.


Purpose of Research:• To investigate

the issues and impact of utilising DGPS coordinate technology applied to cadastral surveys in Queensland.


Current Cadastral Surveying• The cadastral

surveying system depends fundamentally on an accurate correlation of measurements withwithmarks on the ground which relate to the boundaries of land.

• The question of whether marks (monuments) should prevail over measurements as evidence of boundary location is NOT an issue when the evidence provided by measurements and marks are not in conflict.


Current Cadastral Surveying• The

MEASUREMENTS are simply an aid to description and

• boundaries are not altered nor the proprietary rights of land owners altered by an improved description of the land. (Cook 4.6 1992)


Why is GPS being considered for this Application?

• GPS, unlike conventional survey equipment and techniques, does not measure angles and lengths between ground marks.

• Instead, a GPS measuring system (ground component) consists of:– instruments,– observation techniques,– data processing methods– provides 3-D (4-D) vectors between ground marks

relative to World Geodetic System 1984 (WGS 84).


Why is GPS being considered for this Application? (continued)

• Do not need clear “lines of sight” like conventional traversing, but rather a clear view to the sky.– An EXAMPLE: Long lines measured (say 15km) with just 2

establishments using common double-differencing techniques– Re-occupation of marks 12+hours later to meets ICSM class 3-B or

higher standards of accuracy guidelines -ie 2 by 15 minutes for static observation @ 15kms.

• Can be a 1 person field operation using doc. procedure.• Least-Squares network adjustment assigning vector

precision within a network solution• Cost of survey quality GPS equipment is reducing along

with attainable accuracy



Fundamental Methods• Cadastral survey

plans traditionally show bearing and horizontal distances between points describing the parcel boundary.

• Two dimensional in-nature in a local plane projection system

• GPS can provide three dimensional coordinates of point positions in a geocentric reference system.

• Differences of coordinates (positions) transformed to local plane system provides same bearing and distance description.


Problems in Coordinate Descriptions• The use of co-ordinates to specify the

POSITIONS of boundary locations is a very convenient and often efficient method of unique point identification for computer graphic applications.

• GPS derived co-ordinate information must be (and usually is) three-dimensional and four-dimensional.

• However, MUST be updateable information -models of our world improving over time. ie AGD66, AGD84, MGA/GDA starting 2000.


Problems with Coordinate Descriptions

• Relative and historical (time) dependant• Small transcription error in numerical data

can lead to large errors on the ground• must have a measure of co-ord precision• influences of global and regional

geodynamics ie N.Z. dynamic environment.

• Velocity vector - Alice Springs ~7mm per year NNE direction


Routes for Establishing Traceability of GPS

• National Standards Commission and respective state/territory authorities are reviewing situation.

• Currently have ICSM best practice guidelines and SP1 documents

• Working party considered options:– EDM calibration baselines + extended 3-D– Special, dedicated TEST networks*– Geodetic Networks


Routes for Establishing Traceability of GPS • However agreement not reached due to

fundamentals of a GPS measuring system:-•• POSITIONPOSITION as a STANDARD

– Recognised Value Standard (RVS)• Two pre-requisites for success of this approach

for traceability– Position must be accepted as a “physical

quantity” that comes within the scope of the National Measurement Act 1960

– The reference positions must be well known, with adequate accuracy, in a well-defined coordinate system


• GPS Time is traceability back to the SI second and Universal Time.

• Ten points have been gazetted as Australian Fiducial Network -AFN

• Australian National Network -ANN



Concept of Local Controlled Areas • GPS network solutions described in Canadian

introduce local neighbourhood accuracy for survey control - quality measure for positional accuracy relative to a local government area.

• Cook* first introduced concept of LCA for QLD in 1992 in proposed re-organised S&M industry.

• Each LCA contains a computer model of the cadastral boundary layout based on bearing and distances from cadastral surveys together with connections to control survey marks


Concept of Local Controlled Areas • Each computer model is up-datable from within

by incorporating results of a new survey to give “preferred dimensions” for survey adjustment purposes to produce– boundary co-ordinates,– archiving and time-stamping of data for

historical cadastral mapping– monitoring improvements of precision over

time• Each model is responsive to changes in its spatial

control environment with improved knowledge


Concept of Local Controlled Areas • each LCA model is capable of integration with

adjoining models, and long lines which cross from one LCA to the other

• Modelling of regional geodynamics within LCA - currently incorrectly assumed constant and uniform velocity vector (untested hypothesis)

• principal factor in determines the size of an LCA is the need to control the volume of data to allow management by cadastral surveyor responsible for new input of boundary information -traditional, GPS, other etc.


Concept of Measurement Based Concept of Measurement Based Multipurpose Cadastre operating at Multipurpose Cadastre operating at

the Local Controlled Area Level the Local Controlled Area Level • Management of Cadastral Information relates to

the maturity level of survey infrastructure.• Commonly accepted levels:

– Graphical Cadastre ie base level DCDB– Upgraded Graphic Cadastre– Survey Accurate Cadastre– Reinstated Cadastre– Legal Cadastre


Measurement Based Multiple-Purpose Cadastre

• Fundamental concepts are that measurements are first class objects and are primary carriers of metric information.

• Preserving original measurements along with information on the quality of measurements at time of survey.

• Coordinate values (or other) that are required to answer queries are computed from the stored measurements as needed.


Measurement Based Information• With improving

GPS measuring systems, GPS measurement information fits the measurement based cadastre operating over a LCA

• Disadvantage is high initial capital $


Conclusions• Surveyors practising in jurisdictions

which administer large mining, pastoral or marine leases, are already using position-based technologies such as GPS and Photogrammetry.

• It is inevitable that position-basedmeasuring technology and techniques will be increasingly used by surveyors to perform cadastral surveys.

••• Impact of Coordinate Collection Technology on Impact of Coordinate Collection Technology on Impact of Coordinate Collection Technology on Cadastral Surveying Cadastral Surveying Cadastral Surveying by Robert Webbby Robert Webbby Robert Webb

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Impact of Coordinate Collection Technology on Rural ...eprints.qut.edu.au/3950/2/3950b.pdf · Surveying in Queensland Robert Webb Seminar presentation for partial fulfilment towards