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(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)
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 2
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
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 3
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.
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 4
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.
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 5
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.
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 6
Purpose of Research:• To investigate
the issues and impact of utilising DGPS coordinate technology applied to cadastral surveys in Queensland.
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 7
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.
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 8
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)
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 9
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).
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 10
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
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 11
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 12
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.
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 13
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.
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 14
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
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 15
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
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 16
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
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 17
• 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
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 18
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 19
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
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 20
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
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 21
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.
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 22
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
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 23
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.
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 24
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 $
(C)(C)Robert Webb Robert Webb 2000 PLAS:Queensland University of Technology 25
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