FREQUENCY ANALYSIS OF AERIAL THERMAL SURVEYS 
ON SHALLOW WATER: A METHODOLOGY TO DESCRIBE 
GEOMETRIC DISTRIBUTION OF BOTTOM MORPHOLOGY 
L. Alberotanza - C.N.R., Laboratorio per lo Studio 
della Dinamica delle Grandi Masse - San Polo 1364, 
30125 Venezia, Italy 
G. M. Lechi - C.N.R., Istituto per la Geofisica della 
Litosfera - Via Mario Bianco 9, Milano, Italy 
Introduction 
The research présented in this paper represents an ulterior 
contribution to the studies which are being carried on to pro- 
vide information on the elaborate details of the hydrodynamics 
of the Venetian Lagoon. The quantitative data from these anal - 
yses are elaborated on allowing us to obtain the inputs neces - 
sary to improve the models already in use and to better under- 
stand the mechanism of the sea-lagoon exchange. The technique 
of aerial thermal surveys, repeated at regular intervals over 
he same arca, according to an already well-tested methodology, 
gives an extensive amount of information regarding the dynamics 
and evolution aspects. 
Briefly, the purpose of our work is the improvement and a 
consequent verification of the validity of a methodology which 
permits us to elaborate thermal information in terms of har - 
monic analysis, achieving the following objectives: 
1) description of the thermal behaviour of the surfacing areas 
in consequence of the solar heating 
2) description of the preferential ways of the water in the chan 
nels during the tides: since the in going and out going pat- 
terns of the water bodies are different, two hypotheses are 
possible. Or the "return water" follows a different trace, 
or the two velocities are different. 
3) description of the bottom morphology, in shallow water, by 
means of comparison of different and subsequent image fre- 
quencies analyzed (or harmonic analysis).