@staticmethod
def savi_calc(img, const=0.5, scale_factor=10000):
    """ Soil adjusted vegetation index"""
    return img.select(['NIR']).subtract(img.select(['RED'])).multiply(1 + const
        ).divide(img.select(['NIR']).add(img.select(['RED'])).add(const)
        ).select([0], ['SAVI']).multiply(scale_factor).toInt16()
