representation and management of spatial error in cadastral databases dr. panos lolonis manager of...
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Representation and Management of Spatial Error in Cadastral Databases
Dr. Panos Lolonis
Manager of the Planning, Research and Development Division
Coordinator of the Planning and Quality Department
Ktimatologio S.A. (Hellenic Cadastre S.A.)Ktimatologio S.A. (Hellenic Cadastre S.A.)
Mesogion 288Mesogion 288
GR-GR-15562, 15562, Holargos-AthensHolargos-Athens
Tel.: +30-1-6505-829Tel.: +30-1-6505-829E-mail: [email protected]
OutlineOutline
Conventional approach for handling spatial Conventional approach for handling spatial cadastral datacadastral data
Shortcomings of the traditional approachShortcomings of the traditional approachRepresentation of spatial cadastral data and Representation of spatial cadastral data and
their accuracytheir accuracyManagement of data and their accuracyManagement of data and their accuracyUse of stochastic spatial data in land management activitiesUse of stochastic spatial data in land management activitiesConclusionsConclusions
Conventional Approach for Handling Spatial Cadastral Data
Conventional Approach for Handling Spatial Cadastral Data
Lack of accuracy about the locations of cadastral dataLack of accuracy about the locations of cadastral data Use of data in deterministic fashionUse of data in deterministic fashion
Consequences and shortcomingsConsequences and shortcomings Lack of specificity about the level of accuracy Lack of specificity about the level of accuracy
(“more or less”)(“more or less”) Inconsistencies among different series of Inconsistencies among different series of
measurementsmeasurements Inconsistencies among values of documentsInconsistencies among values of documents Problems in the use of cadastral data in applicationsProblems in the use of cadastral data in applications
(zoning regulations, tax agencies)(zoning regulations, tax agencies)
Importance of accurate locational cadastral data
Extract from a ContractDefinition of the size and dimensions of
the parcel
Extract from a ContractDefinition of the size and dimensions of
the parcel
Cadastral Map Land parcels in a city block
Cadastral Map Land parcels in a city block
Cadastral Extract of a Land Parcel Cadastral Extract of a Land Parcel
Cadastral Extract Sent to Owners Cadastral Extract Sent to Owners
Differences between Declared and Computed Areas
Differences between Declared and Computed Areas
0
10
20
30
40
50
60
< (-
50)
(-50
) -
(-20
)
(-20
) -
(-10
)
(-10
) -
(-5)
(-5)
- (
-2)
(-2)
- (
2)
(2)
- (5
)
(5)
- (1
0)
(10)
- (
20)
(20)
- (
50)
> (5
0)
Category
Per
cen
t (%
)
Urban
Rural
A’ Pilot ProgramThe Hellenic Cadastre Project
Municipalities:Urban: Chalandri
Rural: Megas Alexandros
Public Opinion about the Benefits of the Hellenic Cadastre
Public Opinion about the Benefits of the Hellenic Cadastre
Category
• Settlement of the boundaries of the properties of individuals
• Protection from land infringement• Determination of public land• Facilitation of land transactions• Protection of forests• No benefits• No answer
Sample size: 1495Date: December 1999
0
10
20
30
40
50
60
70
1 2 3 4 5 6 7
Category
Perce
nt of
resp
onse
s (%)
Representation of Spatial Cadastral Data and Their Accuracy
Representation of Spatial Cadastral Data and Their Accuracy
Tag standard errors and covariances to the coordinate Tag standard errors and covariances to the coordinate datadata
Computation of derivative variables and their accuracyComputation of derivative variables and their accuracyLengthsLengthsAreasAreasAnglesAngles(Use of the Error Propagation Law)(Use of the Error Propagation Law)
Need to incorporate functions into computer-based Need to incorporate functions into computer-based cadastral systems to handle errorcadastral systems to handle error
Locational Accuracy of Points, Sides and Areas
of Land Parcels
Locational Accuracy of Points, Sides and Areas
of Land Parcels
Area = 1854.84 m2(1834.64 – 1875.03)
Management of Data and their Accuracy
Management of Data and their Accuracy
Adoption of the stochastic frameworkAdoption of the stochastic frameworkprovides new flexible ways to deal with problems provides new flexible ways to deal with problems
and proceduresand procedures requires a different approach to carry-out land requires a different approach to carry-out land
administration tasksadministration tasks
Procedures for updating dataProcedures for updating dataTesting about the coincidence of old and new Testing about the coincidence of old and new
datadataAmalgamate old and new informationAmalgamate old and new information
Use of Stochastic Spatial Data in Land Management Activities
Use of Stochastic Spatial Data in Land Management Activities
Compilation of legal documents (contracts)Compilation of legal documents (contracts) Incorporate expected values, confidence intervals and Incorporate expected values, confidence intervals and
confidence levels into documents and diagramsconfidence levels into documents and diagrams
Satisfying zoning regulations (Test hypotheses)Satisfying zoning regulations (Test hypotheses)::AreasAreas
HHoo: Area >= 400 m: Area >= 400 m22 H H11: Area < 400 m: Area < 400 m22 at the 95% at the 95% confidence levelconfidence level
LengthsLengthsHHoo: Length >= 15 m: Length >= 15 m H H11: Length < 15 m: Length < 15 m at the 95% at the 95% confidence levelconfidence level
Resolving boundary disputesResolving boundary disputes
Need to reform legislation to incorporate the stochastic Need to reform legislation to incorporate the stochastic notions (expected values, standards errors, confidence levels)notions (expected values, standards errors, confidence levels)
Conclusions Conclusions
Accuracy information must be explicitly incorporated and Accuracy information must be explicitly incorporated and handled into cadastral databaseshandled into cadastral databases
Cadastral data that incorporate accuracy measures are Cadastral data that incorporate accuracy measures are more informative and more useful in land management more informative and more useful in land management activitiesactivities
There is a need to promote development of:There is a need to promote development of: GIS software that can handle probabilistic dataGIS software that can handle probabilistic data Legislation that is in conformance with probabilistic Legislation that is in conformance with probabilistic
reasoningreasoning
Goal: To develop cadastral systems that combine data Goal: To develop cadastral systems that combine data about location, accuracy and time in a tightly integrated about location, accuracy and time in a tightly integrated framework.framework.