# Sensitivity Analysis of Multi-Temporal Sentinel-1 SAR Parameters to Crop Height and Canopy Coverage
## 1 Introduction
Interactions between radar configuration (frequency, wavelength, polarity, and incident angle) with each other, as well as its interaction with the plant variables, has made the use and interpretation of radar data useful but complicated [9; 14; 15]. Therefore, in agricultural studies, radar parameters which affect the signal scatter and target parameters that influence the signal propagation should be deliberately investigated. The target parameters mainly depend upon dielectric constant and geometric properties. Dielectric constant is closely related to the plant's water volume, and the shape, size, and orientation of leaves, stalks, and fruits are relevant to geometric properties. Radar wavelengths are sensitive to target parameters [1]. Hence, the preference of microwave data type is one of the substantial issues in agricultural studies. According to their leaf size among the various types of agricultural products and their significant role in the world trading market, maize, sunflower (broad-leaf), and wheat (narrow-leaf) crops are investigated to evaluate the potential of multi-temporal Sentinel-1 SAR data in crop development monitoring. In radar vegetation studies among the crop variables, crop height, and canopy coverage (CC) are two main application objectives. In order to obtain the crop status and predict its efficiency, it is necessary to link each of the variations (phenological changes) with the crop-growing conditions (height and coverage) by applying the scattering mechanisms and parameters. Crop height has a close relationship with crop biomass and growth stages, and it is an important variable for crop development observation, crop identification and yield estimation [7; 16]. CC is used to estimate the influence area of the plant and defined as the percent of a fixed area covered by the crown of an individual plant species to the bare soil in a unit area. The total CC can reach a hundred percent (fully covered) since plants can overlap. [PERSON] et al. [17] investigated the sensitivity of RADARSAT-2 polarimetric SAR (C-band) data using sixteen parameters to crop height and fractional vegetation cover (FVC) variables of corn and wheat. They explored that the corn height and FVC are strongly correlated with SAR parameters at the early growing stage but the correlation is low at the later growing stages. Furthermore, they observed that the sensitivity of SAR parameters to wheat variables (height and FVC) is very low. The study concluded that RADARSAT-2 polarimetric SAR (C-band) data has high potential in crop variables estimation for broad-leaf crops. The Sentinel-1 mission is designed as a two-satellite constellation (Sentinel-1A and -1B) that equipped with a dual-polarized C-band SAR 20 m spatial resolution, and six days revisit time. Besides, the data can be acquired in different operational modes which enable users to access freely available long-term data archive for applications requiring long-range time series analyses. [PERSON] et al. [3] utilized Sentinel-1 dual polarimetric C-band SAR images to study the efficiency of the sensor backscatter patterns for crop growth of maize in Turkey and revealed that the Sentinel-1 dual-polarized data provides useful information regarding plant development for agriculture monitoring and valid crop mapping. The potential use of Sentinel-1 radar data has been studied by [PERSON] et al. [18] to estimate the soil characteristics and vegetation variables in agricultural areas. They reported that the sensitivity of the Sentinel-1 measurements to crop parameters decreases with increasing crop cover growth and variation in vegetation parameters. This study investigates the potential of Sentinel-1 dual polarimetric SAR in estimation and monitoring of crop parameters, namely crop height and CC in an agricultural area.