5 - ADVANTAGES AND LIMITATIONS. PROSPECTS FOR FUTURE DEVELOPMENTS 
Relying on the data presented, the major advantages of lidar technique applied 
to sea investigation and survey are: 
(1) capability of remote high-resolution (10-100 m) monitoring over large 
areas (up to synoptic scale); 
(2) relatively weak dependence upon weather conditions; 
(3) capacity for day-and-night continuous measurements; 
(4) full automatization of measuring and primary data processing. 
These features allow to consider the lidar-fluorosensor as promising tool 
for monitoring in the sea. Recently the airborne lidar system (see Grüner et 
al., 1991) have been accepted in Germany for operational use in the German 
parts of the North and Baltic seas (Dr. R. Reuter, personal communication; see 
also Reuter et al., 1994b). A flight schedule of about 1000 hours per year is 
anticipated. The objects of monitoring are oil spills and chemical discharges, 
as well as chlorophyll, yellow substances and turbidity. 
Nevertheless a number of problems (e.g. see Chekalyuk and Gorbunov, 
1993) must be solved to provide transfer of laser remote sensing from research 
environment to the wide operational use in marine and coastal applications. 
One of the shortcomings of lidar-fluorosensor technique is still some 
difficulties in developing the reliable and universal algorithms for accurate 
estimating practically important characteristics of sounding objects (phyto 
plankton pigments concentrations, biomass, species composition, rate of 
photosynthesis, dissolved organic matter and oil pollution contents in the 
water, thickness of oil film at the surface, etc.). In fact, the problems 
related to data interpretation originate not from drawbacks of lidar technique 
per se. They are defined to a large extent by complex nature of investigated 
objects, as well as by variability of their characteristics in sea 
environment. 
The certain progress have been observed in overcoming these difficulties 
in recent years. The novel approach to discriminating the fluorescence contri 
butions of DOM and oil products is described in (Patsaeva, 1994). The promis 
ing results based on classification of oil spectral signatures were obtained 
by Hengstermann and Reuter (1991, 1994). The lidar implementation of pump-and- 
probe technique for estimates of phytoplankton photosynthetic efficiency and 
chlorophyll was developed by Chekalyuk and Gorbunov (1992b, 1994). The 
problems related to interpretation of laser-induced Chl-a fluorescence are 
discussed in (Gorbunov and Chekalyuk, 1994), relying on theoretical descrip 
tion of primary processes in photosynthetic apparatus of phytoplankton. 
Concerning methodology of lidar application, some problems were caused by 
generally narrow track (less than 1 m) of laser sounding during along-track 
measurements. It complicated the analysis of spatial distributions of 
monitored parameters and limited spatial resolution across the track of 
carrier. The promising way to overcoming the related problems is utilization 
of an optical scanner (Grüner et al., 1991), providing two-dimensional mapping 
and ensuring spatial resolution of 10 m and a swath width of 150 m at the 
operational altitude of 1000 m. 
The common problem typical for majority of remote sensing techniques 
(both passive and active) is inability to provide vertical profiling even 
within near-surface water layer. Although the lidar systems possess an obvious 
potential in this field, for a long time the attempts to implement this were 
based just on detection the backscattered laser irradiation. From this point 
the recent development of shipborne lidar-fluorosensor, capable for time 
resolved spectral measurements looks very promising. The vertical resolution 
of 0.2 m and optical depths of 4 to 6 attenuation lengths have been achieved 
in the field with laser excitation at 532 nm. 
With regard to the platforms, probably a helicopter may be considered as 
the most underestimated potential carrier for lidar-fluorosensor. As this