Cadastral Principles

TCI Workshop17 October 2007

Grenville Barnes

Content• Purpose

• Cadastral vs Geodetic points

• Cadastral System

• Boundary Types

• Cadastral Surveying Process

• Cadastral Evidence

• Heterogeneity Example

• Professional Trends

PURPOSE OF CADASTRAL SURVEYING

• Demarcate and Identify Boundaries

• Collect Evidence to Perpetuate Boundary Location to Promote Security of Tenure

• Obtain Data to Represent Boundaries in an Abstract Form (graphical and mathematic evidence)

     Where is the parcel?

    What size (area) is the parcel?

     What are the dimensions of the parcel boundaries?

     What constitutes the parcel boundaries?

   What is the unique identifier of the parcel

Specific Purpose of a Cadastral System

Multipurpose Land Information System

Geodetic Infrastructure

CadastralDatabase

SurveyRecords

• natural resources• infrastructure• socio-economic

RegistryInformation

Owners/LesseesSource of rights

RestrictionsEncumbrances

Parcel Identifier

Information Layers

Spatial Geo-reference

Framework

Cadastral Survey

Cadastre

INFRASTRUCTURE MEASUREMENT MANAGEMENT

Components of a Cadastral System

The spatial geo-reference framework provides a common reference system for the integration of tenure and other land information.

Cadastral vs Geodetic Points

Location of geodetic points is a question of mathematics (coords may vary if datum changes or through readjustment)

Location of cadastral points (parcel corners) is defined by law and evidence (location depends on interpretation of cadastral evidence, especially physical evidence

Cadastral surveying is the process of defining and describing boundary evidence

Fixed vs General Boundaries

• Fixed - corners/bendpoints are beaconed and boundary is the invisible line in between the beacons

• General – a physical feature (hedge, wall, fence, etc.) is accepted as the boundary and mapped

Point Typology

• Parcel corner beacons

• Indicatory beacons

• Control stations (e.g. traverse) – connection to geodetic network

• Geodetic Control Points

Cadastral Surveying Process

• Prior to fieldwork acquire cadastral data on previous surveys of the parcel and adjoining parcels (Reg. 10)

• Search for original beacons in field • Survey in found monuments and permanently demarcate

control stations (link to geodetic control)• Compare found evidence with previous survey evidence

(measurements, beacons, etc)• Recompute and Replace missing beacons• Document survey (report, coord list, comps, fieldbook,

etc)

How does this change with use of GPS technology??

Cadastral Surveying Challenge

Cadastral boundaries are surveyed by different surveyors at different times to different specifications using different equipment…..

As a result they are a heterogeneous set of points

Can GPS promote homogeneity?

Cadastral Data as Evidence

Mathematical/Measurement

Physical

Graphical

beacons

fencesimprovementswitness marks

distancesangles

coordinatesarea

Index mapSurvey plan

Verbal

Hierarchy of Cadastral Evidence

Field Notes/ Observations

REALITY

Physical Parcel beacons

Computations

Measurements

Coordinates

Survey Plan

Index MapINCREASING

ABSTRACTION

Area Calculation

Beacon description

Incr

ea

sin

g w

eig

ht

of

ev

ide

nce

2

(200)

(150)(150)

(200)

ORIGINAL (PARENT) PARCEL

(Assume that coordinates are fixed in database)

BA

CD

26

27

28

(150’)

(200’)

(200’)

(150’)Rem of 2

147’

198’

Owner of 2 requests three 50’x100’ parcels be subdivided out of parent parcel

A

C

B

D

26

27

28Rem of 2

(200)

49’(150)

(200)

49’

49’

(150)

99’

99’

99’

Surveyor finds A, B and C and several other original beacons and proves thatthese are original, undisturbed and consistent

What happens to the ‘fixed’ coordinates in the database???

Measurements are never exact – they contain systematic and random errors

C

BA

D

FUNDAMENTAL PRINCIPLES

• Equipment is calibrated prior to first use and periodically after that (e.g. 6 monthly)

• Measurement to property corners are checked with independent measurements

• The original survey provides a definitive description of the parcel boundaries

• Relocation of parcel boundaries is determined by a consideration of various evidence

Open Thick bush

Low L

and

V

alue

Terrain/Access

Cadastral Record EvidenceGood Poor

Cad

astr

al

Fie

ld

Evi

den

ce

High

Good

Poor

Most Expensive

More expensive

Least Expensive

Matrix of Rural Survey Cost Components

Surveying Professional Trends

• Develop ‘thin’ Survey/Mapping Department that deals primarily with Quality Control and Project Management

• Contract out surveys to private sector

• Government responsible for geodetic infrastructure

• Emergence of surveying profession (private and public)

Cadastre 2014 – FIG 20 year Vision • Show the complete legal situation of land, including public rights and restrictions.• Separation between ‘maps’ and ‘registers’ will be abolished.• Cadastral mapping will be defunct; it will be replaced by modeling.• “Paper & pencil cadastre” will be replaced by modern technology.• Cadastre will be highly privatized with public and private sector working closely together.• Procedures for definition of private and public land objects will be identical.

http://www.fig.net/cadastre2014/

Reg. 36 (2)(c)

“A surveyor shall not use a loop traverse closing on his starting point if it is practicable to traverse between two previously fixed stations.”