689

respective

ages.

I Infrared and

eff. = s.

ri

.48

-0.16

-54

13

-0.6

-57

18

-0.5b

.60

12

-0.49

0

0.5 0.9 0.7

Graan Rod

0-9 0.9 (ftm) Wavolongth

Infrarad

Figure 5« Diagrams of the mean reflectance derived

from the mean values of the base colour components,

a) Gl, b) G2, c)LG and d) MA. DN stands for Digital

Numbers.

We remark a good matching between the diagrams of the

subframes G2 and LG; we also observe a decreasing of

the mean reflectance from the sub-frame Gl up to MA.

This fact would mean a high correlation between the

response in reflectance of the surely geothermal

zone LG and the zone G2; in both cases thermal IR

surveys indicated zones where EV was very small, al

most zero.

Moreover, the sub-frame MA was the most suspected

area, since it was the only spot indicated at the

same time both by FATI and by EV function solutions.

On the other hand, the sub-frame Gl shows the hi

ghest reflectance values and that could fully be cor

related to the highest values of FATI previously che

cked.

The arithmetic means of each band ratio have been

correlated to their standard deviations (see fig.6),

We remark here that arithmetic means of NDVI sub

frames keep almost the same values. That confirms the

spots selected show similar vegetational vigour and

the mean values of actual NDVI are ranging between

0.15 and O.bk which correspond to the middle levels

in the grey scale of fig. 4.

Moreover, a noticeable difference appears in the

mean values of the IR/Green ratio between G2 and LG;

on the contrary, their respective reflectance featu

res shown in figure 5, resulted to be almost the sa

me. That means the ratio IR/Green has a more discri

minating power than the ratio IR/Red and than the

spectral signature alone.

In particular, the site MA shows the highest values

in both ratios and, at the same time, it also pre

sents the lowest reflectance mean values in according

to the basic concept of a general decay when vegeta

tion is submitted to the presence of geothermal fl

uids.

255-1

240-

M

220-

200-

180-

160-

* 140-

•K

1*1

Í

120-

100-

80

60

40-

20-

0-

1

^1

-4

o ^

O «N

Q O

% —

* -

o K,

O Uj

<0 1

?£

JO .

Ï £

e> o

O Q

o Î

O

$

:a 1

Î §

Figure 6. Diagrams of the mean values of band ratios

at different sites, a) IR/Red, b)lR/Green, c) NDVI

and d) standard deviation amplitude.

These arguments authorize to take the suspected zone

MA Poggio Mauriccia into a higher consideration than

the other sub-frames.

Scattergrams of data also have Deen analysed, al

though no particular indication has outcome beside

the high correlation that has been found between the

Green and Red images, almost in all 4 cases. Scat-

tergrams of band ratios IR/Green and IR/Red con

firmed the lowest correlation is found for the

subframe MA.

4 CONCLUSIONS

The application of the Derived Tbermal Quantities

method in the Travale geothermal field has given so

me unexpected results.

At first, neither the old field of Lagoni nor the

new one to the north have been particularly pointed

out in relation to othen surrounding areas. That gi

ves rise to some perplexity on the validity of the

method.

Nevertheless, some otber interesting indications

have been provided. Although the checked sub-frames