685
Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986
Digital analysis of stereo pairs for the detection
of anomalous signatures in geothermal fields
E.Zilioli, P.A.Brivio, M.A.Gomarasca & R.Tomasoni
Istituto per la Geofisica della Litosfera, CNR, Milan, Italy
ABSTRACT: A campaign of infrared aerial surveys for mapping heat flow anomalies was performed in the geother
mal field of Travale (Italy). Direct methods of quantitative analysis of thermographies and deduction of seco
ndary physical quantities were applied: three spots of possible geothermal interest have "been individuated.
Further investigation was developed on the basis of spectral signature of vegetation; a third flight was ac
complished in springtime to provide infrared false colour stereo-pairs at i/12,500 scale. Color transparencies
have been scanned by a drum microdensitometer and a quantitative computation was carried out. The suspected
areas so identified have been compared to other spots where ground and depth conditions are known.
1 PREVIOUS WORK
This paper deals with the remote sensing activity in
the frame of the Energy Project sponsored by the Na
tional Research Council of Italy.
Previous work is here summarized:
Data Acquisition. Campaigns included 2 thermal IR
surveys by a dual-channel analogue scanner DS-1230
realized at the steady-state conditions of the diu
rnal thermal transitory, in wintertime. During the
flight operations meteorological stations were arr
anged for corrections and calibrations. A stereo IR
False Colour coverage was acquainted on the same a-
rea in springtime.
Thermal Data Processing. The black-body referenced
thermographies were digitized and a correlation be
tween the calibration temperature levels and the Di
gital Numbers (DN) was obtained (Bolzan et al. 1982).
Table 1. Summary of spectral bands utilized .
Means
Wavelength ( ym)
Band
0.5-0.6
Green
Photography
0.6-0.7
Red
0.7-0.9
near IR
1.0-2.O
near IR
Scanner
4.5-5-5
middle IR
9.5-11
thermal IR
By means of calibrated thermographies we obtained 3
new derived quantities we called Function of Appare-
nt Thermal Inertia (FATl), Entropy Variation (EV)
and Sensitivity (s) respectively (Zilioli et al.
1985). The common solutions of these equations indi
viduated 3.spots on the ground of possible geother
mal interest.
2 DESCRIPTION OF THE SUSPECTED AREAS
Location of the suspected areas is shown within the
frames outlined in fig. 1. According to the classi
fication by Pavari (19^2), the study area is inclu
ded in the phytoclimatic belt of Italy: Castanetum,
Figure 1. Location of the study area. Frames and sub-
frames are pointed out.
subzone cold with Quereus spp deciduous woods and de
fined by a hilly zone ranging between 300 and 800 me
ter. Land use is about 75% forested and the remaining
25$ pasture and sown, almost distributed on the right
and on the left slope'Of the Saio creek basin, respec
tively.
