Index: ../trunk-jpl/src/c/classes/kriging/Observations.cpp
===================================================================
--- ../trunk-jpl/src/c/classes/kriging/Observations.cpp	(revision 17341)
+++ ../trunk-jpl/src/c/classes/kriging/Observations.cpp	(revision 17342)
@@ -379,20 +379,24 @@
 	IssmPDouble* A = xNew<IssmPDouble>((n_obs+1)*(n_obs+1));
 	IssmPDouble* B = xNew<IssmPDouble>(n_obs+1);
 
+	IssmDouble unbias = variogram->Covariance(0.,0.);
 	/*First: Create semivariogram matrix for observations*/
 	for(i=0;i<n_obs;i++){
 		for(j=0;j<=i;j++){
 			A[i*(n_obs+1)+j] = variogram->Covariance(x[i]-x[j],y[i]-y[j]);
 			A[j*(n_obs+1)+i] = A[i*(n_obs+1)+j];
 		}
-		A[i*(n_obs+1)+n_obs] = 1.;
+		A[i*(n_obs+1)+n_obs] = unbias;
+		//A[i*(n_obs+1)+n_obs] = 1.;
 	}
-	for(i=0;i<n_obs;i++) A[n_obs*(n_obs+1)+i]=1.;
+	for(i=0;i<n_obs;i++) A[n_obs*(n_obs+1)+i]=unbias;
+	//for(i=0;i<n_obs;i++) A[n_obs*(n_obs+1)+i]=1.;
 	A[n_obs*(n_obs+1)+n_obs] = 0.;
 
 	/*Get semivariogram vector associated to this location*/
 	for(i=0;i<n_obs;i++) B[i] = variogram->Covariance(x[i]-x_interp,y[i]-y_interp);
-	B[n_obs] = 1.;
+	B[n_obs] = unbias;
+	//B[n_obs] = 1.;
 
 	/*Solve the three linear systems*/
 #if _HAVE_GSL_