80 
‘over 
City area 
) of 1981, 
mages of 
istortions 
ormation 
Nearest 
category 
ze pixels 
ory. The 
is shown 
increases 
sation. 
  
60 
Cover 
21.2. Relation of UI with the Density of Building 
Cover. 
Building cover data was obtained from a 1:12672 (16 
chains to one inch) map of Colombo City and environs of 
1970. This map was scanned and the percentage of 
building cover or urban density (UD) values were 
computed. UD was defined as the percentage of the total 
number of pixels representing buildings within a rastor 
grid cell of 650mX650m. The scanned image of building 
cover was registered with the Landsat TM image. The 
average UI values for the same rastor cells coresponding 
to the UD values were computed. Areas that have been 
urbanised after 1970 were identified using information 
from the Colombo City Development Plan of 1985 and 
new building cover maps which are under preperation. 
Then using UD values from the areas in which the 
building cover has not changed much during the past two 
decades the scatter diagram of UI with UD was obtained 
as shown in figure 4. 
  
  
  
  
100 
e 
| e 
80 EN * e, 
um es d ^. e 
| ee *" % 
vo 
40 P e 
20 1 | | 
0 20 40 60 80 
UD (%) 
Figure 4. Relation Between UI and Urban Density 
In concluding the verification of the index UI it could be 
said that UI is strongly related to the density of built-up 
land and therefore is an appropriate index that could be 
used to evaluate urbanisation. 
3. SOCIO-ECONOMIC AND ENVIRONMENTAL 
DATA USED 
Data of population, housing, labour force water supply 
consumption, electrical energy consumption, land values 
and environmental related diseases relating to the 
administrative geographical units in the Colombo 
Metropolitan Region was used. The data relate to the 
period 1991 to 1994. The boundaries of the geographical 
units to which data of water supply consumption, land 
values and electrical energy consumption are related are 
different from the others because of different planning 
units adopted by the relevant administrative authorities. 
323 
Hence, this data is shown in tables 2.3 and 4 respectively. 
The other data shown in table 1 relate to administrative 
areas (A.G.A Divisions) shown in figure 5, within the 
Colombo Metropolitan Region. They cover a land area of 
1386 Sq.km and has a total population of approximately 3 
million. 
The environmental related diseases that have been 
considered are Dvsentry, Entric Fever, Viral Hepatitis, 
Malaria, Diarrhoea, Leotos Pirosis and Wooping Cough. 
Data of reported cases of these diseases in the 
administrative areas of the Colombo Metropolitan Region 
for the period 1992 to 1994 has been obtained from the 
Epidemiological Unit of the Colombo General Hospital. 
From this data disease intensity in each area has been 
computed by considering an annual average of the total 
number of reported cases of all of the above mentioned 
diseases. 
  
  
  
  
  
Figure 5. Administrative Units in the Colombo 
Metropolitan Region 
4.0 RELATION BETWEEN UI AND 
SOCIO-ECONOMIC AND ENVIRONMENTAL 
DATA. 
To compute UI values an image of 4000X2550 pixels was 
used. Average UI values for pixels of 2X2 Landsat TM 
pixels were computed and this image was registered with 
digitised maps showing the boundaries of the 
administrative units in the Colombo Metropolitan Region 
(CMR). The average UI value for each administrative 
area was then calculated. The relation between UI and 
the socio-economic and environmental data 
corresponding to the geographical units in the CMR is 
shown in the scatter diagrams of figures 6 to 12. 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996