The approach which includes the analysis of thermal data 
  
  
  
  
  
  
  
  
  
  
   
  
  
  
   
  
  
   
    
together with its frequency permits us to reduce the survey 
of sea truth in cases in which one must operate in very shal- 
low water under difficult navigational conditions. The "non 
thermal" use of data that is primarily thermal, becomes permis- 
sible with frequency analysis which in reality is no more than 
a description of surface textures of a body of water. As far 
as it coneerns the importance of the effects of the boundary 
layers. 
Technique 
  
  
n Six flights, each one at an hour's interval, were made to 
| closely follow the tide flow during a complete tide phase 
(fig. 1) in the northern part of the Venctian Lagoon, along the 
natural water canal of San Felice. The importance of this 
canal in hydrodynamics is that it is connected directly with 
the sea through the canal of the Lido Port supplying an area of 
the lagoon for more than fifty square kilometers. 
jo cm 2 
0 6 12 TIME 
Flight numbers for the corresponding tide phase.