Although there are lots of parameters affect on computing the depths of the sea, rivers and oceans by the reflectance value from the satellite image. The attenuation coefficient is still the most important parameter, because all other parameters have same value in the study area in opposite to the attenuation coefficient. This value was computed for the river Nile, which is our focus of this study. The attenuation coefficient changes by changing the amount of water impurities and the concentration of the algae in it. Due to heterogeneity of water of the river Nile, so while calculating the attenuation coefficient, we depend on the natural properties of the river Nile which check the natural diversity for the values of the attenuation coefficient. It is usual that the attenuation coefficient in the shallow water changes from that in deep water and both change from pure water, where the algae is found in very small amount and decreases in it the amount of impurities. We used in our study satellite image from (geo-eye) with resolution 1.65m. The image covers 15 Km from the river Nile, also we used the mathematical model for computing the depths by depending on the attenuation coefficient value for both the blue and the green band for each study area. Also we used the echo sounder for measuring the depths and comparing them with the computed depths. In this research, we used the remote sensing technique reflectance's values for geo-eye satellite sensor for estimating the attenuation coefficient of the river Nile, by using the water attenuation mathematical model through the observed field depths by echo sounder instrument as reference. The estimated depths were obtained with a relatively low difference versus the traditional depths. |
