the costs. 
3.3 Demarcation and surveying 
Demarcation is usually carried out in two approaches 
involving legal and technical surveying aspects. 
In the first approach the boundaries are recognized 
on the ground, surveyed or identified on aerial 
photographs but neither legally fixed nor permanantly 
demarcated if this is not requested by the parties. 
In the second approach the exact positions of 
boundaries are fixed on the ground in the presence of 
the parties, and permanently marked with pipes, 
stones, concrete beacons etc. if existing fences, 
hedges or ditches are not considered sufficient 
demarcation. 
Depending on the choice of boundary concept, one 
can have many alternatives on the data capture 
methods. If one would consider a large area for 
systematic adjudication, aerial photography might be 
most economically appropriate. 
For example, in Kenya, enlarged aerial photographs 
are adopted for preliminary index diagram where the 
boundaries of each parcel are marked and verified in 
the field. In Thailand, rectified enlarged photographs 
are used to identify parcel boundaries in the flat areas. 
The problem on such method is that photographs are 
not rectified to correct relief displacement. Secondly 
the areas derived from such documents would not be 
appropriate. Thirdly boundaries would not be 
retracable in case of disputes, because there were not 
measurements recorded. If database is to be 
established from such documents, digital monoplotting 
would be recommended provided that auxiliary data 
(such as digital elevation model, orientation 
parameters and ground control points) are available in 
the light of low cost approach. 
An alternative approach is to prepare a large scale 
topographic database using photogrammetric 
techniques and cadastral boundaries are then marked 
on these digital topographical maps in the field using 
physical features as control points. Then a simple 
method of digitizing or construction procedure can be 
effected in the database. 
There are many countries where the ground survey 
methods such as compass or optical square and tape 
measurments, compass-angle instrument, theodolite 
and stave, and electronic distance measurement 
(EDM) and theodolite, are being employed. Now-a- 
day global positioning system (GPS) is also a popular 
data capture method for cadastral purposes. 
In some developing countries (eg Nepal and Bhutan), 
planetabling technique is still used to prepare 
cadastral maps in the field. In such cases quality is 
limited to map scale, map quality, accuracy of control 
points used, and skills of the surveyors. 
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B3. Vienna 1996 
In Zambia, the freehold parcel boundaries are usually 
surveyed using theodolite and either steel tapes or 
EDM with high standards of measuring accuracy 
ranging from 1:4,000 (rural areas) to 1:12,000 (urban 
areas) for the traversing with complete measurement 
of parcel dimension in the field. In other situation, a 
simple sketch plan is made for a short term leasehold 
land and no boundaries exist or marked on the 
ground. 
In general the quality of such spatial cadastral 
boundary data depends on: 
- the choice of boundary concept, 
- the method of identification of boundary, 
- identification errors, 
- method of data capture and conversion, 
- data structure or storage and 
- etc. 
Further elaborations on quality issues will not be dealt 
in this paper. 
3.4. Uses of PBIS 
The parcel database should be suitable for use in 
many of land related applications apart from the basic 
land registration and cadastre already discussed 
above. 
Some of main land related applications are Property 
convenyancing, land reform, utilties, valuation and 
taxation, land consolidation, development planning 
and management, statistical analysis, environmental 
protection, etc. These applications uses cadastral 
parcels by combining with other spatial objects 
specified in their models. 
In this connection, it is quite interesting to see 
description given by H Couclelis ( 1996) on "a 
typology of perspectives on boundaries" from the 
user views. 
4. UNCERTAINTY ISSUES 
In GIS there are many research publications and 
literatures, which treat uncertainty aspects. The 
intention of this paper is to relate and highlight some 
of these concepts within cadastral application 
domains. The following figure shows data elements 
which are influenced by the uncertainty, because they 
are either due to the concepts that were adopted, 
method of data capture and conversion, classification 
Schemes, the way data are organized and stored, or 
interpretation on the data for many cadastral 
applications.