Suitability of Multidate ERS - 1 SAR Data for
Crop Acreage Estimation
P. V. Narsimha Rao, K. Sreenivas, K. V. Ramana and L. Venkataratnam
Agriculture and Soils Group, NRSA
Hyderababd-500 037, India
Abstract
Use of remote sensing data acquired in visible and infrared wavelengths in crop studies is widely known. However, sensors operating in these wavelengths to provide clear data in the presence of clouds in general and along the coastal areas during monsoon period in particular. Microwave remote sensors such as Synthetic Aperture radar (SAR) on board ERS-1 satellite, have all weather capability and provide cloud free data. In view of this, an attempt has been made to study the suitability of multidate ERS-1 C-band SAR data alone for crop classification and acreage estimation. The radar data acquired at 35 day interval during 1992-93 rabi crop season, were geometrically corrected and filtered for speckle suppression. Then a maximum likelihood classification was carried out on multidate data sets. The classification results sow that better discrimination of classes like paddy, coconut, current and permanent fallow fields is possible with three date data set. This could due to the changes associated with various classes during the data acquisition period that aid in the discrimination of these classes. However, no clear discrimination could be observed between pulses and tobacco corps consideration of texture information, a characteristic of radar data, may improve discrimination between these crops evaluation of results obtained from single and two date data sets show poor classes. Results are discussed and compared against those obtained by IRS LISS - II data classification as well as BES statistics.
Introduction
Use of remote sensing data acquired by remote sensing satellites like IRS-1, LANDASAT and SPOT in the visible and infrared wavelengths in crop studies is widely known. However, sensors operating in these wavelength bands fail t provide clear date in the presence of clouds during monsoon season in general and along coastal areas in particular, rendering remotes sensing of crops difficult. On the other hand, microwave sensors such as Synthetic Aperture Radar (SAR) onboard ERS-1 satellite have all weather capability and provide cloudfree data. Potential of microwavedata for crop identification and acreage estimation has been one of the research topics all over the world with the launch of ERS-1 satellite with C-band SAR sensor. In view of this, an attempt has been made of study the suitability of ERS-1 SAR data acquired at 35 day interval during the 1992-93 rabi season. The main objective of the study has been to use microwave data alone for crop classification and acreage estimation and compare the results against those obtained by suing IRS LISS - II data of the same period. In the process, sparability of major classes in the study are was studies based on the measures such as Jeffries Matusita distance for multidimensional data sets and a pair of classes for single dimensional data sets.
Study Area
Study area is a part of East Godavari district in A.P. covering an area of 2.15 lakh acres and ten revenue mandals with major land use and land cover being crops like paddy, pulses (black gram and green gram), tobacco, paddy fallows and permanent fallows, orchards like cashew and mango, coconut and settlements. The study area is characterized by unirrigated red and black soils in the north and irrigated medium black sols in the south.
