Improve reverse model

common/utils/dt_model.c

@@ -80,7 +80,8 @@ double dt_model_azimuth_delta(double az, double el)
 double dt_model_azimuth_delta_rev(double az, double el)
 {
 	/* No reverse model available, (ab)use the forward model */
-	return -dt_model_azimuth_delta(az, el);
+	return -dt_model_azimuth_delta(az - params->a0 - params->c1/cos(2*M_PI*(el-params->e0)/360.),
+                                       el - params->e0);
 }
 
 double dt_model_elevation_delta(double az, double el)
@@ -98,7 +99,8 @@ double dt_model_elevation_delta(double az, double el)
 double dt_model_elevation_delta_rev(double az, double el)
 {
 	/* No reverse model available, (ab)use the forward model */
-	return -dt_model_elevation_delta(az, el);
+	return -dt_model_elevation_delta(az - params->a0 - params->c1/cos(2*M_PI*(el-params->e0)/360.),
+                                         el - params->e0);
 }
 
 int dt_model_init(void)