947 
Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986 
Land suitability mapping with a microcomputer using fuzzy string 
J.P.Wind & N.J.Mulder 
ITC, Enschede, Netherlands 
INTRODUCTION: In this report a system is described which allows digitizing, editing and storage of land units 
in a database. Land suitability for selected crops is mapped on a color raster screen by selecting a color 
code for suitability mapping. Intervals are defined on the attributes as strings. 
The measure for suitability for a certain crop is derived in two possible ways: 
1. For each suitability class the required properties )strings) are matched (AND-function of (un)equal 
property values of crop and land unit) against the land unit property table; an exact match produces the 
choosen color on the screen. 
2. For one crop the ideally required properties are matched against the land unit property table (string) but 
a measure or (mis)match is given based on the Hamming distance of the property strings. Each distance can 
by assigned a different color. 
1. HOW TO MAKE A LAND SUITABILITY MAP. 
To obtain a landsuitability map the following steps 
have to be taken: 
a. digitize/edit land unit boundaries (free 
digitizing). 
b. define/edit list of centroids vs. land units. 
c. generate a list of map attributes. 
map unit: soil depth: salinity: ph: 
for each attribute generate a menu of allowed 
attribute values (text strings): 
attrl. menu: 
soil depth 
0 
to 
5 
cm 
5 
to 
10 
cm 
10 
to 
20 
cm 
20 
to 
40 
cm 
40 
to 
80 
cm 
> 
80 
cm 
d. Generate a table with lines containing: 
map unit, attributel, attr.2 
Relation table II 
Crop requirements: 
crop class soil depth ph attr.3 
pat at 
good 
> 
80 cm 
7 
" 
med. 
5 
to 
10cm 
6 
ft 
bad 
0 
to 
5 cm 
5 
beets 
good 
> 
80cm 
6.8 ... 
" 
med. 
20 
to 
40 cm 
5.0 
ft 
bad 
10 
to 
29cm 
4.8 
good 
• • 
to 
. . cm 
Relation table III 
Crop suitability vs colour: 
crop 
class 
red 
green 
bleu 
Patat 
good 
255 
255 
000 
ft 
med. 
128 
128 
000 
" 
bad 
32 
32 
00 
Beets 
good 
000 
255 
000 
ft 
med. 
000 
128 
000 
and for each attribute select an attribute value 
from the current attribute value menu using the 
cursor, move to the next attribute next menu etc. 
Relation table I 
Map unit attributes 
map unit 
soil depth 
ph of attr.3 
name 
soil 
Aal 
5 to 10 cm 
7.0 
Bai 
> 80 cm 
5.2 
e. Generate a table relating crop suitability to map 
unit attributes. 
For the attributes choose for each attribute a 
value from the menue for that attribute. 
f. For each required crop type and range of 
suitability classes define a colour code: 
g. For all crop classes compare the attributes 
required (strings) with the map unit attributes 
(strings) available, if all attributes match then 
link the suitability colour coding table III 
through to the centroid table IV expanding the 
proper map units in the proper colours or: 
map the per pixel map unit number through the 
colour look up table into the right colour. 
Relation table IV 
centroid 
xc.yc 
map unit 
number 
map unit 
code 
123,987 
0 
Aal 
345,6241 
0 
Aal 
23,719 
1 
Ba2 
998,34 
2 
Pq9 
321,789 
255 
ZwO