294
Table 1. Number of available and suitable images, compared with theoretically possible number of satellite
overpasses from April through September, for two irrigation districts, Grande Bonifica Ferrarese and East
Sesia, from 1980 through 1985
Year
Path/row
Sensor
Over
passes
Available
images
Images cloud
free in 4
quadrants
Images cloud
free in the
relevant
quadrants
Suitable images
in relevant
quadrants from
April to Sept.
Number of
required
images for the
investigation
num
ber
% of
total
num
ber
% of
total
num
ber
% of
total
num
ber
% of
total
Grande
Bonifica
Ferrarese
1980
206/29
MSS
41
22
53.7
3
7.3
4
9.8
4
9.8
3
207/29
MSS
41
24
58.5
5
12.2
7
17.1
5
12.2
3
1981
206/29
MSS
40
7
17.5
not available
7
17.5
6
15.0
3
207/29
MSS
40
5
12.5
not available
5
12.5
5
12.5
3
1982
206/29
MSS
33
12
36.4
not available
6
18.2
4
12.1
3
207/29
MSS
33
12
36.4
not available
4
12.1
3
9.1
3
1983
192/29
MSS
26
20
76.9
4
15.4
6
23.1
1
3.9
3
1984
192/29
MSS
42
24
57.1
2
4.8
4
9.5
3
7.1
3
TM
19
15
78.9
1
5.3
2
10.5
2
10.5
3
1985
192/29
MSS
46
37
80.4
6
13
14
30.4
10
21.7
3
TM
23
19
82.6
2
8.7
5
21.7
4
17.4
3
East Sesia
1980
209/28
MSS
41
24
58.5
2
4.9
4
9.8
3
7.3
3
1981
209/28
MSS
40
13
32.5
not available
6
15.0
5
12.5
3
1982
209/28
MSS
33
13
39.4
not available
4
12.1
3
9.1
3
1983
194/28
MSS
26
18
69.2
3
11.5
4
15.4
1
3.8
3
1984
194/28
MSS
42
38
90.5
2
4.8
5
11 .9
4
9.5
3
TM
19
17
89.5
1
5.3
3
21.1
2
10.5
3
1985
194/28
MSS
46
42
91.3
7
15.2
13
28.3
6
13.0
3
TM
23
21
91.3
5
21.7
7
30.4
3
13.0
3
Figure 1. Attainment of 100% ground cover in the irrigation district Grande Bonifica Ferrarese in Italy, dur
ing the growing season of 1985 ; A. cumulative distribution of area of occurrence for sugar beet; [t^, t^ ] such
as to give [ACt^) - A(t^)] = 0.8 A(t^); B. durations [t^, t^] and [t^, 12] for each crop
overlap between the periods [t-|, 12 ] applying to each
crop will be rather large, thus complicating crop
discrimination on the basis of multitemporal reflec
tance measurements. We can make discrimination eas
ier by accepting a higher risk of misinterpretation.
So, on the basis of a graph of A(t) (Fig. 1A) we can
estimate a time period [t., ¿2] < [t^, 12] such as to
include 80%, say, of A(t2l. The left and right 10%-
tails are left out of consideration, thus accepting
the implied risk of misinterpretation. We can final
ly obtain a crop calendar (Fig. 1B) giving for each
crop and stage both the duration [tj, t2] and [t^,
£2]- Note that these intervals of time are not the
actual duration at an individual field of the
phenological stage 'attainment of full ground cover'
They indicate that period of time within which a
