diff --git a/src/xsarsea/windspeed/cmod7.py b/src/xsarsea/windspeed/cmod7.py
index 33876ef..e818563 100644
--- a/src/xsarsea/windspeed/cmod7.py
+++ b/src/xsarsea/windspeed/cmod7.py
@@ -56,9 +56,6 @@ def _raw_lut(self, **kwargs):
         final_dims = ['incidence', 'wspd', 'phi']
         coords = {'incidence': inc, 'phi': phi, 'wspd': wspd}
 
-        self.wspd_step = 0.2
-        self.inc_step = 0.2
-        self.phi_step = 1
         self.wspd_range = self.wspd_range_lr
         self.inc_range = self.inc_range_lr
         self.phi_range = self.phi_range_lr
diff --git a/src/xsarsea/windspeed/models.py b/src/xsarsea/windspeed/models.py
index 1e3c9e1..390fe26 100644
--- a/src/xsarsea/windspeed/models.py
+++ b/src/xsarsea/windspeed/models.py
@@ -40,9 +40,9 @@ def __init__(self, name, **kwargs):
         self.wspd_step_lr = kwargs.pop('wspd_step_lr', 0.4)
         self.phi_step_lr = kwargs.pop('phi_step_lr', 2.5)
 
-        self.inc_step = kwargs.pop('inc_step', 0.2)
-        self.wspd_step = kwargs.pop('wspd_step', 0.2)
-        self.phi_step = kwargs.pop('phi_step', 2)
+        self.inc_step = kwargs.pop('inc_step', 0.1)
+        self.wspd_step = kwargs.pop('wspd_step', 0.1)
+        self.phi_step = kwargs.pop('phi_step', 1)
 
         self.__class__._available_models[name] = self
 
diff --git a/src/xsarsea/windspeed/windspeed.py b/src/xsarsea/windspeed/windspeed.py
index bf7940f..ca13510 100644
--- a/src/xsarsea/windspeed/windspeed.py
+++ b/src/xsarsea/windspeed/windspeed.py
@@ -182,13 +182,22 @@ def __invert_from_model_1d(inc_1d, sigma0_co_db_1d, sigma0_cr_db_1d, dsig_cr_1d,
                 one_sigma0_cr_db = sigma0_cr_db_1d[i]
                 one_dsig_cr = dsig_cr_1d[i]
                 one_ancillary_wind = ancillary_wind_1d[i]
+
+                #  if incidence is NaN ; all output is NaN
                 if np.isnan(one_inc):
                     out_co[i] = np.nan
                     out_cr[i] = np.nan
                     continue
 
+                #  if ancillary is NaN, copol & dualpol are NaN
+                if (not np.isnan(np.abs(one_sigma0_co_db)) and np.isnan(np.abs(one_ancillary_wind))):
+                    out_co[i] = np.nan
+                    out_cr[i] = np.nan
+                    continue
+
                 if not np.isnan(one_sigma0_co_db):
                     # copol inversion available
+
                     i_inc = np.argmin(np.abs(np_inc_dim-one_inc))
                     np_sigma0_co_lut_db_inc = np_sigma0_co_lut_db[:, :, i_inc]