diff --git a/src/transmissionReconstruction/dataPreperation.cpp b/src/transmissionReconstruction/dataPreperation.cpp
index 351dcdf..19dce2e 100644
--- a/src/transmissionReconstruction/dataPreperation.cpp
+++ b/src/transmissionReconstruction/dataPreperation.cpp
@@ -22,8 +22,8 @@ namespace Recon
         auto idx2 = Aurora::sub2ind(Aurora::size(aMWaterTempR), {aVrl, aVmp});
         auto waterTemp  = Aurora::zeros(idx1.getDataSize(),1);
         for (size_t i = 0; i<idx1.getDataSize(); ++i) {
-            waterTemp.getData()[i] = (aMWaterTempS.getData()[(int)idx1.getData()[i]]+
-            aMWaterTempR.getData()[(int)idx2.getData()[i]])/2;
+            waterTemp.getData()[i] = (aMWaterTempS.getData()[(int)idx1.getData()[i] - 1]+
+            aMWaterTempR.getData()[(int)idx2.getData()[i] - 1])/2;
         }
         return waterTemp;
     }