International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004 Witexna 
. 9 i 
Figure 5 illustrates the overall architecture of the prototype as Eure‘ 
gure 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
28 
implemented, whilst Figure 6 illustrates the process of iransmi 
progressive transmission from the server to the client. the ares 
Manipulation 
Data stream and rendering Respon 
Tere The res 
Simplification ... Vertex; |vertexy E eve submitt 
ata 
Reconstruction by the c 
Server side Network » T(resp 
Client side +T,(r 
Figure 6. The progressive transmission data from server to Tolquer 
client stateme 
: : | ; i transmi: 
On the client side, data manipulation and rendering and (render. 
reconstruction threads and querying threads run in parallel once side. 7 
the initial transmission of low level data is complete. Thus, as Figure 7 Progressive transmission of vector data operatic 
data is downloaded the user can perform exploratory (e.g., on Athe 
panning and zooming) and querying (e.g., attribute of polygon, Figure 7 clearly illustrates both the progressive increase in 
area of polygon) operations. detail at different levels of detail and the fidelity of the fepreset 
intermediate levels of vector data. Figure 8 shows the number T (res; 
5. EXPERIMENTAL ANALYSIS AND of polygons with different areas for the three stages of ; 
PERFORMANCE TESTING transmission. +T, (ar 
A prototype was developed in Java to test the performance of nid T, (sim 
the progressive transmission algorithm and to check the validity & sumplify 
of the algorithm. Figure 7 illustrates three different phases of EE ~~ -Level 1 A used to 
. M os . . . + | apes (2 LEN 
the progressive transmission visualization procedure on the : sian a à the rum 
client side using data illustrating political (municipal) borders in en j * x compar 
Switzerland (a total of 3062 polygons). E m FX if X with/wi 
= JN) 3 Le v \ 
quf - S. j \ experim 
200 NN. i ; server r 
J . 
"ud based in 
100 pret Resol 
LET km2 1200. 
0 a . - T x $ Are: f 
Areas 0 
e a o 2 f 2 4 
2 : Ze, ; he e uM ans A “a, Ry a ^ be 1000 
2 ‘Oy 4 - 
800 
Figure 8 The number of polygons with different areas at three 
stages of transmission 600 
a2 
E 400 
S : * 
3 |- — - Level-1 5 200 
= -a— Level-2| X 
g 8 ---a--- Level-3 JE 
= jt 0 
re T 
it Figur 
E igure 
i t 
4- jo. 
1 1 e 
fV A eso 
pa As f ud 1800 
2 7 X ‘ 1 i Ara 
" B= Ld / fr 5 
NZ \ r^ Tn pot! e^ i y a 1600 
à kj NE, 1-4 1400 
14205 2425116 7 8.9 10,11.12 13.14 15 16 17.18 19:20 24 22 23 24 
The ID of polygon 1200 
Figure 9 Area of 24 polygons at three stages of transmission 1000 
. ~ ^ . 800 
It is clear from Figure 8 that the numbers of the polygons in the 
ii. 60 
three stages of transmission (Level 1, Level 2 and Level. 3), 2 
which are located in the same area range do not vary greatly. 400 
For example, in the three stages of transmission, the numbers of 200 
polygons which have an area between 1.0-2.0 km? are 506, 438, 5 
b) and 423 respectively. Therefore, the procedure of the 4 
transmission is able to maintain the shapes of the polygons. Fi 
igure