914
2.5 Allocation of land
5.3 Sat
In many developing countries, small parcels of land
have been allocated to the previously landless people.
While this allocation has occured because it meets
certain political and other promises, the impact is to
reduce the land available for commercial agriculture and
to leave these people at or below subsistence level. It
has also meant that large areas of land are put under
pressure with erosion and other environmental problems
occurring.
3 RECORDING THE SPATIAL DIMENSION
As stated previously control can be provided from
existing data or it may have to be specially surveyed
as a framework to control the multiple data.
3,1 Position of the cadastral boundary
There is a need to use numerical control to enable the
position of the resources to be established. The
cadastral boundary can provide adequate control
especially where the land holdings are small.
3.2 Extension of national trigonometrical control
Where there is no numerical control provided by the
cadastre then there will be a need to densify the
trigonometrical network. The positioning of control at
a spacing of better than 800 metres (National Research
Council 1980) will be required.
3.3 Determining control
Where the control is not adaequate and has to be
provided a Global Positioning System (GPS) can be used
■for determining horizontal control to better than one
metre accuracy. This control will be adequate for
many purposes and may well be able to control the
aerial photographs and satellite images especially if it
is in the form of pre-marking or can be recognised on
the image and used for post-marking.
Vertical control will be required for controlling the
aerial photographs and satellite images (especially
SPOT) and will also be needed for resources that are
recorded in height, water heights, water table, flood
limits etc.
4 THE MULTI-PURPOSE CADASTRE
The multi-purpose cadastre will contain a variety of
information in addition to that required for boundary
demarcation, and will assist in the efficient
administration of the land (Bullard 1981). The land
parcel is the basic unit in a MPC.
4.1 The land parcel
The land parcel is the smallest piece of land that is
recorded in a land register. The size of parcels vary
from the very large, the 'latifundi' (Jacoby 1971) to
the very small, the 'minifundi .
Where possible, resources should be related to each
parcel of land. With the 'minifundi' this may not be
possible because the resolution of satellite imagery is
not adequate; this will be achieved with aerial
photography where the scale is suitable.
4.2 The multi-purpose cadastre
The MFC can be thought of as a series of planes each
containing land related data. Figure 1 (Archer 1980)
shows an example of the MFC depicted as 6 planes that
'V
are registered by control.
The property lines are the cadastral boundaries that
depict the individual land parcels. The addresses or
the property descriptions must be such that they
provide a unique description such that there is no
duplication within a property register and, ideally,
within a country.
The base map shows the improvements, houses, and the
surface construction, streets etc. The utility lines
show the position, three dimensionally recorded, of the
network of services.
Flood plains will be determined with the aid of
vertical control.
Land use is recorded as well as zoning which will
relate to the legislation that is enforced to control
activity that may be carried out on a parcel or parcels
of land. The boundary (artificial) between the rural
and urban zones will be of particular interest.
Dependent on the imagery some of the above data may
be established except for adresses. The recording of
property boundaries will be limited to large scale
aerial photographs or where they are depicted by tonal
changes on airborne imagery.
5 AERIAL PHOTOGRAPHY AND SATELLITE IMAGERY
5.1 Aerial photography
The limitation of the aerial photograph for determining
rural resources is that it is in analogue format while
much of the other data in an MPC is in digital format.
It is possible to convert the aerial photograph into
digital format by scanning but with a resultant loss in
resolution. The photograph is also usually only
available in single band format, mainly panchromatic.
The aerial photograph is, like the other imagery,
weather dependent.
5.2 Airborne thematic mapper
It is suggested that the Airborne Thematic Mapper (ATM)
will provide data sufficient for many of the rural
resources. An example is the Daedelus scanner which
can provide digital data with a resolution of better
than one metre and in eleven bands including thermal
infra-red. Unlike the scanner carried in a satellite,
the airborne model is flexible in that it can be
transported to an airfield nearest to a site and await
suitable flying conditions. Cost may, however, be a
limiting factor in using the ATM.
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