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The search strategies used in developing the
system were forward and backward search
methods. ‘To match the method of search that
an expert has in mind while conducting image
interpretation, the main method of search used
in this project was backward chaining.
The primitive units of a class representation is
a number of attributes and goals. The class
was the landform and the attributes were
topography, drainage, tone, gullies, vegetation,
and laboratory tests (i.e. identification elements
used in this research). Primitive facts are linked
in conditional sentences by rules (IF-THEN-
ELSE). The following is an example of typical
rules in the system:
IF The Topography OF The Image IS Flat table rocks
AND The Drainage OF The Image IS Angular dendritic
AND The Tone OF The Image IS Light banded AND The
Gullies OF The Image IS Few to none AND The
Vegetation OF The Image IS Barren THEN The Landform
: = "The Landform is Sandstone"
3.5 System Testing
The system passed through two phases of
evaluation. The first phase was a debugging or
editing phase. It started as soon as the
knowledge engineer began to program the
system and continued until the system was
completed. The second testing phase was an
evaluation process of system performance as
compared to certain reference (e.g. human
expert). This stage was conducted when the
system was operational and ready be delivered
to the end users.
4. SYSTEM IMPLEMENTATION
The major components of this system includes:
input data, inference mechanism, user interface,
output and feed back modules. Figure 1 shows
these components.
The sets of input data were acquired by image
interpretation. In this expert system one goal
was assigned for identifying the expansive soil.
The task of the inference mechanism while
51
conducting an application session may be
viewed as intelligent tracking of a goal from a
collection of classes, attributes and their
method, rules, demons, displays and data bases.
Class allows the developer to reference and
control the functions, flags, and current states
of an application. The goals of an agenda
contain attributes that can be linked to method,
display, rule and conclusions.
4.1 Case Study For System Implementation
Tabouk was selected as a sample area in Saudi
Arabia. It undergoes severe problems due to
expansive soil (Al-jawhra, 1989). Tabouk soil
is expanded as soon as it has some water
content. Its drainage system is so poor. It is
impervious soil. Due to poor permeability and
due to existence of minerals that help expansion
of soil in Tabouk, poor civil engineering
locations must be identified. Accordingly, the
problem in this research was defined as
follows:
Tabouk contains expansive soils that require
experts to define it in the real world and to
inform people about its impact and poor
suitability for civil engineering projects.
For this study, Tabouk area (Figure 2) was
divided into 4 regions. Two of the regions were
used to obtain data necessary for the
development of the system (see Figure 3). The
other two regions were used to test the system.
The major concepts explained so far for
developing the system were executed on the
two regions assigned for the development.
That is, problem identification, data acquisition
and data presentation were conducted using the
acquired information from the two regions of
the case study area. Samples of collected,
processed, and prepared data for system
development are presented in Table 1.
Moreover, many images were processed for the
study area. Sample of these images are seen in
Figures 4 and 5. Also, laboratory tests of soil
and field visits participated as important data
for the development.
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996