diff --git a/Utilities/otbossim/src/ossim/projection/ossimRpcModel.cpp b/Utilities/otbossim/src/ossim/projection/ossimRpcModel.cpp
index 9989c888928ff70ff9f49f4ae233a1d128d1ccc3..c9c4dcee5ff8f52081fab90bd0cc7ec4b89f530f 100644
--- a/Utilities/otbossim/src/ossim/projection/ossimRpcModel.cpp
+++ b/Utilities/otbossim/src/ossim/projection/ossimRpcModel.cpp
@@ -282,7 +282,7 @@ void ossimRpcModel::worldToLineSample(const ossimGpt& ground_point,
 
    if( ground_point.isHgtNan() )
    {
-      nhgt = (theHgtScale - theHgtOffset) / theHgtScale;
+      nhgt = (- theHgtOffset) / theHgtScale;
    }
    else
    {