LAND SUITABILITY MBPS 
SLOPE X 
DEFINE ATTRIBUTE TABLE 
^|S? E T^iiy iNG TflBLES 
MAT OH TABLES 
»DISPLAY MRPS 
PRINT MAPS 
MAP DIGITIZING 
CENTROID NAMES 
DIRECTORY 
STOP 
UB1 B.0-2.8 
UB2 8.0-2.0 
UB3 0.0-2.0 
TM 
AA 
AO 
AC 
RE 
AU 
EM 
0.0-2.8 
0.0-2.8 
2.0-8.8 
25.8- 55.8 
8.8- 2.0 
8.8-2.8 
2.8-8.8 
8.0-16.8 
16.8-25.8 
Figure 2.1 Menu choice by cursor movement (black box 
is cursor). 
Fig. 2.5 
Values of attribute ’slope’ per landunit, 
displayed on screen. 
red 
blue 
yellow 
Fig. 2.2 Possible colours and patterns 
DEFINE ATTRIBUTE TABLE 
NEW TABLE 
EDIT TABLE 
■DISPLAY TABLE 
LOAD TABLE 
STOP 
Fig. 2.3 Function choice by cursor 
DISPLAY TABLE 
SLOPE X 
8.8-2.8 
2.0-8.0 
8.0-16.0 
16.0- 25.8 
25.0- 55.0 
Fig. 2.4 Attributee from attribute table with its 
values displayed on a screen. 
h. Overlay the land suitability map with any 
required line or symbol information. 
i. Desing the colour legend. 
,j. Save the colour coded suitability map as an image< 
file for further processing or hardcopy 
production. 
k. Future extension: 
kl: the map unit unit attributes contain 
numerical values like: soil-depth= 17 (cm) 
k2: the crop requirement attributes contain an 
expression to be evaluated like: 
IF soil-depth > 12 or soil-depth < 32 THEN 
condition=TRUE 
Match is TRUE if all attribute requirements 
evaluate to TRUE (AND of all partial 
evaluations). 
REMARKS: EXPERT SYSTEM. 
In putting an expression evaluator in the table of 
required attributes we have implemented an expert 
system for land suitability evaluation. 
The program evaluating the expression for attributes 
required is in fact a rule intepretor. 
The table with map units and attributes together 
with the polygon data form the geographical data 
base. 
The table with required attributes for crop 
suitability classes forms the actual rule base or 
knowledge base. 
2. HOW DOES IT LOOK LIKE. 
In this section different screen dumps are shown of 
the actual presentation. 
Every choice that must be made is done by displaying 
the possible choices on the screen in a menu and 
indicating the choice by moving the cursor up and 
down (see fig. 2.1). 
2.a Map digitizing and editing. 
Map digitizing is done by so called "free 
digitizing". This means that lines are not stored as 
vectors, but the entire image is saved pixel by 
pixel. It also can be stored by run length coding, 
bo tnere is no line indication. To delete a line or 
a polygon a square rubber can be put on the screen 
which can be moved by the cursor on the tablet to 
what must be deleted. By pressing one of the buttons 
the area under the rubber is deleted (i.e. becomes 
black/white). One can choose between three rubber 
sizes. 
To plot a line three colors can be choosen. To fill 
a polygon with a color, a color fill subroutine is 
written which fills a polygon from the centroid with 
a color pattern (for color pattern see figure 2.2). 
Once a polygon is actually filled it can not be 
filled with another pattern. The digitized map can 
be printed on a color inkjet printer in two sizes 
using the full or the half width of the paper. 
2.b Attribute definition. 
To make a land unit table (table I, section 1) and a 
crop requirements table (table II, section 1) first 
an attribute table has to be made. By cursor 
movement one of the functions (figure 2.3) can be 
choosen. A new table can be defined or an existing 
table edited. For each attribute its values are 
asked. The values are stored as strings. Each 
attribute and its values can be shown on the screen 
(figure 2.4).