Full text: Remote sensing for resources development and environmental management (Volume 1)

155 
h histogram 
W rÛL 
icy histogram 
R-B not on LFC 
h histogram 
rHftufliïT 
icy histogram 
MJ 
h 
"C not on SIR 
tents: 
present on LFC 
ent on SIR-B. 
tr to it overre- 
Sudan, the sun 
îun elevation of 
in both cases 
>nt: 50 E from N 
■B and 40 E from 
illumination is 
for sunlight on 
he radar energy 
E lineaments on 
d, volume scat- 
1 be less than 
parameters four 
;re made: 
ited from SIR-B 
:rom SIR-B image 
ireted from LFC 
from LFC photo 
jroups (fig. 9) 
rations : a broad 
row peak around 
c directions are 
classes). 
Table 3. Results of the x 2 test for four groups of 
directional classes. 
I 
II 
III 
IV 
I 
- 
25.5* 
96.3 
124.2 
II 
25.5* 
- 
107.8 
110.6 
III 
96.3 
107.8 
- 
30.6* 
IV 
124.4 
110.6 
30.6* 
- 
df : 17 (degrees of freedom) 
* Ho: Distribution similar, differences due to 
random errors. 
To determine if significant differences occur 
between the groups of directional classes, a x 2 test 
is used (table 3). 
As can be expected, comparison of groups I and II 
(both from radar interpretation) gives a small 
variance of 25.5. 
We can accept the hypothesis (Ho) that no signi 
ficant differences occur between the samples and 
that the differences are due to random errors. The 
same is true for Groups III and IV (both from LFC 
interpretation). Comparisons of Groups I and III, I 
and IV, and II and III give rather high values, so 
the null hypothesis has to be rejected and the 
samples have to be considered as different. 
Considering the contribution of the different 
directional classes to the total variances it can 
be seen (table 4) that midclass directions 310° and 
320° and midclass directions 50° and 60° cause the 
principal differences. For comparison of Group I 
and III (all radar lineaments and all LFC lin 
eaments) , the directional classes 310°-320° of the 
observed frequencies for radar interpretation are 
considerably higher than the expected frequencies 
according to the null hypothesis, whereas for the 
LFC photo-interpretation they are lower. For direc 
tional classes 50°-60°, the reverse is true; here 
the observed frequencies on radar are much lower 
than the expected frequencies according to null 
hypothesis. 
Apparently the enhancement of lineaments oriented 
perpendicular to the radar look direction causes 
the overrepresentation. The direction perpendicular 
to the sun azimuth for the LFC photo apparently is 
of no influence, because this direction is under 
represented. Radar look direction (50°) is of nega 
tive influence in lineament detectabilty as was 
expected, but sun azimuth direction for LFC seems to 
have little influence. 
Comparing Groups II and III (only radar lineaments 
not present on LFC and all LFC lineaments), the con 
tribution to the variance is still even larger for 
the directional classes parallel and perpendicular 
to the radar look direction. In directional class 
50° (radar look direction) , not a single dike lin 
eament has been observed on radar which was not also 
visible on the LFC against 30 lineaments on the LFC 
image not interpreted from radar. 
Considering the LFC lineaments not present on 
radar in comparison with the distribution of all 
radar lineaments (Groups IV and I), we again see the 
negative influence of radar look direction on lin 
eament detectibility. In direction 310°-320° and 
340°, an overrepresentation of lineaments is found 
on the radar image; 310°-320° is partly due to the 
radar azimuth orientation, but the 340° direction 
may be a result of penetration through superficial 
sand cover. 
CONCLUSIONS 
In the Iranian case, the differences in length re 
cognition of the strike ridges interpreted from 
radar and from hand-held camera images are largest. 
Nearly double the length (28 km) can be seen on 
Table 4. Contribution to variance for different 
directional classes. Midclass direction: 
Group I/Group III Group II/Group III 
w 
270 
.12 
.11 
W 
1.80 
.66 
280 
.00 
.00 
.36 
.13 
290 
1.27 
1.15 
3.20 
1.22 
300 
2.72 
2.47 
.25 
.09 
310 
6.34+ 
5.75- 
18.23+ 
6.73- 
320 
8.62+ 
1 
M 
00 
r- 
21.24+ 
7.84- 
330 
.74 
.67 
5.07 
1.87 
340 
1.13 
1.03 
.00 
.00 
350 
1.71 
1.55 
1.33 
.49 
N 
0 
1.19 
1.08 
N 
.30 
.11 
10 
.75 
.68 
1.58 
.58 
20 
.34 
.31 
.07 
.03 
30 
.64 
.58 
2.70 
.99 
40 
2.55 
2.31 
4.62 
1.71 
50 
13.05- 
11.84+ 
12.94- 
4.78+ 
60 
7.56- 
6.86+ 
4.34 
1.60 
70 
1.76 
1.60 
.31 
. 11 
80 
.00 
.00 
.30 
.11 
E 
E 
Total 
= 96.3 
Total = 
107.8 
Group II/Group IV 
Group I/Group IV 
W 
1.27 
1.04 
W 
.09 
.18 
.02 
.02 
.09 
.19 
.72 
.59 
.08 
.16 
.14 
.11 
.99 
2.01 
12.13+ 
9.96- 
4.10+ 
8.28- 
9.55 
7.85 
3.05+ 
6.17- 
2.13 
1.75 
.17 
.34 
2.29 
1.88 
3.45 
6.96- 
.01 
.01 
.01 
.02 
N 
1.69 
1.39 
N 
.03 
.07 
.36 
.30 
.03 
.05 
.03 
.03 
.00 
.00 
1.35 
1.11 
.02 
.05 
4.03 
3.31 
1.81 
3.66 
13.53- 
11.11 
11.93- 
24.11+ 
11.25- 
9.24+ 
14.82- 
29.93+ 
.11 
.09 
.02 
.03 
.09 
.08 
.45 
.91 
E 
E 
Total 
= 110.6 
Total 
= 124.2 
+ Observed frequency considerably higher than 
expected frequency according to null hypothesis. 
- Observed frequency considerably lower than 
expected frequency according to null hypothesis. 
radar before the strike ridges seem to disappear 
under the superficial sand cover. The ground resolu 
tion of the SIR-A image is much better than that of 
the hand-held shuttle photography. Unfortunately, no 
more detailed images or field observations have been 
obtained over this area, so that no conclusive de 
duction could be made regarding possible penetration 
of microwaves through superficial sand cover. 
In the arid area of the eastern desert, Egypt/Red 
Sea hills, Sudan, the study of length and frequency 
of dike swarms in sandy areas did not conclusively 
reveal penetration capability of microwaves through 
aeolian sands to reveal lightly covered dike struc 
tures. In most cases, frequency and cumulative 
length of interpreted dikes from the SIR-B images 
was smaller than that interpreted from LFC photo 
graphy. Both types of images have approximately the 
same order of spatial resolution (approximately 20 
m). The tonal range of the LFC photos is larger and, 
moreover, they can be studied in stereo, giving them 
a slight advantage for interpretation. Only in area 
3 was a higher frequency of radar lineaments found. 
Close visual comparison of the two interpretations 
gives the impression that penetration of microwaves 
through superficial sand cover has resulted in a 
larger number of detectable dikes on the radar 
image.
	        
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