The following points highlight the nine main factors affecting remote sensing. The factors are: 1. Amount of Suspended Sediment 2. Turbulence of Water 3. Amount of Chlorophyll 4. Temperature 5. Mineral Composition 6. Soil Moisture 7. Organic Matter Content 8. Soil Texture 9. Size and Shape of the Soil Aggregate.
Remote Sensing: Factor # 1.
Amount of Suspended Sediment:
Higher visible reflectance results, if the water has a large amount of suspended sediment present, when compared to clearer waters.
Remote Sensing: Factor # 2.
Turbulence of Water:
The amount of energy absorbed and transmitted is also affected by turbulent water.
Remote Sensing: Factor # 3.
Amount of Chlorophyll:
The amount of water reflectance is also affected by the amount of chlorophyll. An increase in green wavelengths and a decrease of blue wavelengths results due to an increase in the amount of chlorophyll. The concentration of algae present in a water body can be detected and estimated by remote sensing.
Remote Sensing: Factor # 4.
Reflectance of water is affected by temperature variations throughout the day.
Reflectance data for water bodies has been used to detect a number of water pollutants e.g. oil and industrial wastes, and to determine the presence or absence of tannin dyes from the bog vegetation in lowland areas. Certain water characteristics such as salt concentration, pH, dissolved oxygen concentration, etc. cannot be observed directly with water reflectance changes but can be correlated with observed reflectance
Remote Sensing: Factor # 5.
The reflectance spectrum is affected by the mineral composition of soil. Increasing reflectance of soil occurs from the visible to the short-wave infrared – with, absorption bands around 1.4 µm and 1.9 related to the amount of moisture in the soil.
Remote Sensing: Factor # 6.
Soil moisture affects the spectrum and the ration between the spectral bands. Spectral bands of red and near-infrared bands are independent from the soil moisture. If the soil is moist, radar waves may not be able to penetrate the soil and in such cases soil moisture will develop parallel curves on the soil reflectance spectra.
The soil line of the soil reflectance spectra, characterizes the soil type, defines vegetation indices, and corrects the plant canopy reflectance’s from the optical soil property effects.
Remote Sensing: Factor # 7.
Organic Matter Content:
It may indirectly affect the spectral influence, based on the soil structure and water retention capacity. High organic matter in soil may result in spectral interferences for band characteristics of minerals like Mn and Fe.
Remote Sensing: Factor # 8.
Soil Texture (Surface):
Soil optical properties are affected by the rough soil texture, as light is trapped in the rough surfaces of the coarse soil particles. For example, a stronger reflectance is received if iron and lime are present, than if the soil material is fine textured and dry. Variation in soil reflectance also occurs where there is a change in distribution of light and shadow areas with surface roughness areas.
Remote Sensing: Factor # 9.
Size and Shape of the Soil Aggregate:
The reflectance properties are also influenced by soil size and shape. A decrease in reflection results when the size of a soil aggregate expands in diameter. The surface texture depends on the shape of the soil aggregate. Instead of a jagged soil aggregate, a more spherical soil aggregate results in a smooth and even surface.
Satellites that provide images to help achieve soil classification include:
(i) Land sat MSS — It allows for discrimination between the moist and dry soils.
(ii) Land sat TM high-resolution imagery — It provides useful information on soil mineralogy and arid areas.