Table 4 
Area (A) and number (N) of polygons 
code Ns Ns As4 (ha) Asx(ha) 
112 86 86 11632 12041 
121 19 19 1565 1581 
122 3 3 186 186 
131 11 7 429 340 
132 2 2 78 78 
133 1 0 79 0 
141 1 47 47 
142 4 4 136 185 
21i 60 51 86919 87119 
221 16 21 2047 2177 
222 10 9 741 628 
231 112 114 13704 12598 
242 41 40 6885 6845 
243 51 53 4771 5071 
311 67 63 19184 19849 
312 6 7 236 322 
313 6 7 197 278 
321 5 5 163 163 
324 26 17 1397 787 
411 18 20 1653 1736 
511 l 1 414 370 
512 14 15 1136 1200 
Total: 560 545 153600 153600 
  
  
  
  
  
  
  
Ay - area of class "1" before updating (date T1) 
Ap, - area of class "i^ after updating (date T2) 
AT - total area of the database 
Nj; - number of polygons of class "i" before updating (date T1) 
Np - number of polygons of class "i" after updating (date T?) 
Typical questions of statistics are: 
e How large is the change in the number of polygons for class 
“7 
e How large is the area increase/decrease for class “i”? 
These questions can be answered easily by comparing summary 
statistics of CLC databases for both dates (Table 4). 
Table 4 includes e.g. an area growth in non-irrigated arable land 
[211] and broad-leaved forest [311] classes, while the number of 
polygons in those categories have decreased The area of 
discontinuous urban fabric [112] increased, while the polygon 
number remained unchanged. The area loss was noticeable in 
pastures [231], transitional woodland-scrub [324] or orchard [222] 
categories, and the single occurrence of construction site [133] 
disappeared. 
e How large is the change in the area/number of polygons 
between class “i” and class ^j" ? 
The evolution matrix (contingency table) as the most detailed 
statistical descriptor can answer these questions (Table 8). Diagonal 
values in the evolution matrix indicate no-change, while off-diagonal 
values show transitions between CLC classes during the eight years 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Table 5 
Normalised changes (ordered) 
code | Asa-As4 | [Asz-As4]/As4 | rate of change 
(percent) (percent/year) 
133 -79 -100,00 -12,50 
324 -610 -43,67 -5,46 
131 -89 -20,65 -2,58 
222 -113 -15,23 -1,90 
511 „44 -10,62 -1,33 
231 -1106 -8,07 -1,01 
242 -40 -0,59 -0,07 
141 0 0,00 0,00 
321 0 0,00 0,00 
132 0 0,00 0,00 
122 0 0,00 0,00 
211 200 0,23 0,03 
121 16 1,02 0,13 
311 665 3,47 0,43 
112 409 3,51 0,44 
411 83 5,01 0,63 
512 64 5,60 0,70 
243 299 6,28 0,78 
221 130 6,37 0,80 
142 49 35,69 4,46 
312 85 35,97 4,50 
313 81 41,34 517 
  
  
  
  
  
period. Some categories, like road and rail network [122], dump sites 
[132], green urban areas [141] or natural grassland [321] remained 
unchanged. High values in the matrix (and in similar matrices for 
percentage of area or number of polygons), show significant 
transitions, €.g. between non-irrigated arable land [211] and pastures 
[231], or broad-leaved forest [311] and transitional woodland-scrub 
[324]. The matrix shows many area-exchanges between agricultural 
land [211, 221, 222, 231, 243]. The non-irrigated arable land [211], 
pastures [231] or broad-leaved forests [311] classes have been 
transformed to several different categories. 
e Which are the classes with the most significant area changes 
per year? 
e Which are the most dynamic classes? 
e — Which classes are updated more than the average and less than 
the average? 
These questions help to make a reliable comparison between changes 
derived for areas of different size, different time span or both. To 
answer them, specific indicators were computed (ETC/LC, 1997). 
.  Relativeareachange: = C;=| Ai2z— Air |/ Air 
It answers the question: Which are the most increasing or 
decreasing classes in terms of area under the updating period? 
This indicator can be normalised using the number of years 
elapsed between T; and T? (Table 5). It shows 100% relative 
area loss in case of class 133, which is the consequence of 
transformation of the single construction site polygon into 
settlement [112]. A significant relative area loss is observable in 
transitional woodland- scrub [324] or mineral extraction site [131] 
688 International Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998 
  
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