diff --git a/Applications/Radiometry/otbOpticalCalibration.cxx b/Applications/Radiometry/otbOpticalCalibration.cxx
index 0aea2b6473fa3e081150888ec99989c7f4218182..1a8b7957089c27a3e5cfc10b1524c8a4576bbac8 100644
--- a/Applications/Radiometry/otbOpticalCalibration.cxx
+++ b/Applications/Radiometry/otbOpticalCalibration.cxx
@@ -344,6 +344,8 @@ private:
                             "compute adjacency effects, it doesn't have to"
                             "match the image spacing");
     SetMinimumParameterFloatValue("atmo.pixsize",0.0);
+    SetDefaultParameterFloat("atmo.pixsize", 1.);
+
     MandatoryOff("atmo.pixsize");
 
     // Doc example parameter settings