“…Over the last decades trigonometric models on the plane, where under the signs of cosines and sines are linear forms of two variables with unknown frequencies as coefficients, have received special attention in the literature on signal and image processing due to their wide applications in the analysis of symmetrical textured surfaces. See, for example, Rao, Zhao, and Zhou (1994), Kundu and Mitra (1996), Zhang and Mandrekar (2001), Kundu and Nandi (2003), Nandi, Kundu, and Srivastava (2013), Ivanov and Malyar (2018), Ivanov and Lymar (2020).…”