Analytical algorithm

which is based on bio-optical model

represents the trends of algorithms in retrieving water quality parameters from remote sensing data.In analytical algorithm

inherent optical properties

including absorption coefficients and back-scattering coefficients of each component of water

are important input parameters.The absorption coefficients of each component of water can be measured easily in laboratory.On the other hand

the measuring of back-scattering coefficients of suspended matter in water is always difficult

especially for inland waters.There are mainly three kinds of methods in measuring back-scattering coefficients of suspended matter:（1） measuring in field with specific instruments;（2） collecting water samples in field

measuring the scattering phase functions of the water samples in laboratory

and then calculating the back-scattering coefficients based on the scattering phase functions;（3） collecting water samples in field

measuring the total absorption coefficients and beam attenuation coefficients of the water samples

and then calculating the back-scattering coefficients by substracting the total absorption coefficients from beam attenuation coefficients

and then multiplying ratio of back-scattering coefficients of suspended matter.However

all these three methods have some drawbacks:（1） these methods are mainly designed for ocean waters

and may not be suitable for inland waters due to the great differences in optical properties between them;（2） the scattering phase function measuring instrument is hard to be designed and installed

and there are few such instruments in China;（3） the ratio of back-scattering coefficients of suspended matter

which is difficult to measure

has to be estimated in calculating back-scattering coefficients of suspended matter

and the estimation will lead to some errors.In this paper

a new method of calculating back-scattering coefficients of suspended matter is put forward.Based on bio-optical model

this method uses the water surface reflectance spectra data and absorption coefficients of water components to retrieve back-scattering coefficients of suspended matter.Validated by data acquired from Meiliang Bay

Taihu Lake

this method shows advantages as follows:（1） based on bio-optical model

it has sound theoretical basis;（2） it is easy to be carried out because the data used in this method are easy to obtain.Provided the above advantages

data of back-scattering coefficients of suspended matter can be acquired for the application in the future.