When doing a point to area SNR prediction at 0.1 degree resolution, the contour values does not seem to be smooth over the prediction area. There are boundaries where there is a large delta change in SNR values. I am using isotropic/dipole_14mhz_10m_aagl.13 antenna, Any reason for this?

When doing a point to area SNR prediction at 0.1 degree resolution, the contour values does not seem to be smooth over the prediction area. There are boundaries where there is a large delta change in SNR values. I am using isotropic/dipole_14mhz_10m_aagl.13 antenna, Any reason for this?
