Decision-Making in the Legal and Technical Realm

1. Decision-Making in the Legal and Technical Realm The Cadastral Case Gerhard Navratil GeoGeras, 3./4.7.2006

2. The Problem • Cadastre • Public inventory of pieces of land, provides identifiers to register rights on land (Henssen and Williamson 1990) • Socio-technical system (Ottens 2004, Stubkjaer 2006) • Systems require decisions within processes – legal and technical approaches • Do the approaches work along the same lines? • Hypothesis: No!

3. Outline • Decision-Making • Practical Example • Principles • Implications • Conclusions

4. Decision-Making • „choosing between two or more alternative courses of action“ (Yntema and Torgerson 1961) • Questions in cadastre • Where is the boundary? • Is the boundary unchanged? • Who is the owner? • … • Decisions based on answers to questions • Strategy different in legal realm than in technical realm

5. Legal Realm • Decisions made by humans without additional tools • Subdivision in small, simple decisions • Questions: • Who makes the decision? • Are applicants allowed to ask for a decision? • Which rules are applicable? • To what decision do the rules lead?

6. Technical Realm • Data comes from observation  not error-free • Standard method: Statistics • Adjustment computation (regression analysis): Over-determined observations  estimated values and distribution parameters • Test statistics allows to make statements

7. Practical Example (1) • Case reported by Twaroch (2005): Distance building – boundary • 3.96 m is too small if 4.0 m are necessary

8. Practical Example (2) • Let‘s assume coordinates • Tape measure: 3.99 m • Distance between line 12 and point P‘: 3.96 m • Distance between line 1‘2‘ and point P‘: 4.01 m

9. Legal Solution • 1. Step: Checking the boundary • 2. Step: Determine the distance • Use coordinates of points 1 and 2 for the boundary and P‘ for the building • Use a tape measure Decision maker uses one method  Decision: Too close

10. Technical Solution (1) • Compute distance with 1, 2, P‘ and determine standard deviation (first order Taylor method): 3.96 m, s=12.8 cmBased on sc=10.0 cm • Statistical test of hypothesis larger than 4.0 m with 95%: Accepted! • Reject requires sc=1.6 cm

11. Technical Solution (2) • Determination of correspondence of boundary: Deformation analysis • Local – global movements • Requires unchanged geometry of control points and unchanged observation strategy

12. Principles: Process • Legal decision-making • Done without tools • Can be done by amateurs • Series of simple decisions • Technical decision-making • Uses mathematics • Done by experts only • Provides optimal result

13. Principles: Errors • Legal decision-making • Uses previous decisions • Appeal (only for errors in process) • In special cases new decision (only if new evidence and decision in serious doubt) • Technical decision-making • Uses previous data • Assumes existence of random deviations • Can be reconsidered (other parameters optimized)

14. Implications • Cadastral data: Based on observations  contains random deviations • Legal processes only assume gross errors and cannot cope with random errors • Coordinates fixed unless proved wrong • Observations with smaller random errors cannot improve the data

15. Conclusions • Legal and technical decision processes can lead to different results • Legal status of coordinates in the technical system ‘cadastre’ merges technical and legal strategies • Mixing legal and technical aspects causes problems • Values for coordinates are a technical problem  solution must be purely technical (measurement-based cadastre)