diff --git a/w-stacking.cu b/w-stacking.cu
index f52889a37fd597ba08328a00c9c75ad7c5efd13c..9aa0d6684489352a5f173330f08be64257ec39a2 100755
--- a/w-stacking.cu
+++ b/w-stacking.cu
@@ -159,7 +159,7 @@ __global__ void convolve_g(
       for (k = kmin; k <= kmax; k++)
         {
 
-	  double v_dist = (double)k - pos_v;
+	  double v_dist = (double)k+0.5 - pos_v;
 	  int increaseprecision = 5;
 	  
 	  for (j = jmin; j <= jmax; j++)
@@ -472,13 +472,13 @@ void wstack(
       for (k = kmin; k <= kmax; k++)
         {
 
-	  //double v_dist = (double)k+0.5 - pos_v;
-	  double v_dist = (double)k - pos_v;
+	  double v_dist = (double)k+0.5 - pos_v;
+	  //double v_dist = (double)k - pos_v;
 
 	  for (j = jmin; j <= jmax; j++)
             {
-	      //double u_dist = (double)j+0.5 - pos_u;
-	      double u_dist = (double)j - pos_u;
+	      double u_dist = (double)j+0.5 - pos_u;
+	      //double u_dist = (double)j - pos_u;
 	      uint iKer = 2 * (j + k*grid_size_x + grid_w*grid_size_x*grid_size_y);
 	      int jKer = (int)(increaseprecision * (fabs(u_dist+(double)KernelLen)));
 	      int kKer = (int)(increaseprecision * (fabs(v_dist+(double)KernelLen)));