Abstract
ABSTRACT: The measurements obtained by remote sensing are influenced by issues related to relief. Based on that, this paper aims to analyze the spatial and temporal dynamics of the net radiation (Rn), considering the influence of topographic parameters on it, in Edgardia Experimental Farm (FEE). It was used the methodology based on the SEBAL algorithm (Surface Energy Balance Algorithm for Land) to estimate the net radiation by orbital images. In order to assess the topographic influence on the computing of net radiation, three methodologies were applied: without topographic correction (RnSem), cosine correction (RnCos) and C correction (RnC). These methodologies were applied on 21 images of the orbital platform Landsat-5/TM, from 1985 up to 2010. Due to the complex relief of the FEE, the cosine correction did not show effectiveness on the attenuation of topographic influence. For the values of RnC, we noticed an average reduction of 5.97% for the standard deviation, relative to the images without correction. These results show the importance of considering the relief, to achieve higher accuracies on the estimation of biophysical parameters with orbital images.
Highlights
Biophysical parameters obtaining through remote sensing has been of great value for the decision making of public agencies and rural companies
The study was carried out at the Edgárdia Experimental Farm (FEE), located in the city of Botucatu, State of São Paulo (Figure 1), which belongs to the Agronomic Sciences College (FCA) of the Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP)
According to the same authors, the cosine correction would have greater applicability in soil that have slopes lower than 25 ° and lighting angles smaller than 45 °
Summary
Biophysical parameters obtaining through remote sensing has been of great value for the decision making of public agencies and rural companies. A large number of researchers in the area of Agrarian Science have used geotechnologies in recent years to better understand the spatial dynamics of their studies (Andrade et al, 2014; Di Pace et al, 2008; Li et al, 2013; Lima et al, 2012; Menezes et al, 2009; Oliveira et al, 2014; Santos et al, 2014; Silva et al, 2005 and Sousa, 2014). Obtaining consistent values with orbital images depends on the radiometric quality of the data which is directly related to the atmospheric interferences and to the surface illumination conditions (slope areas) at the moment of the satellite passage (Lima & Ribeiro, 2014; Richter, 1998). It is necessary to attenuate these interferences, mainly in multitemporal studies that are related to the classification of the soil cover and biophysical parameters obtaining from the environment. When the objective is to evaluate the dynamics of a given phenomenon over time, there is a need to homogenize the external conditions to the analysis (Chavez Jr., 1988; Hantson & Chuvieco, 2011; Ponzoni et al, 2012)
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