Index: trunk/SDToolBox/output_data.py
===================================================================
diff -u -r76 -r79
--- trunk/SDToolBox/output_data.py	(.../output_data.py)	(revision 76)
+++ trunk/SDToolBox/output_data.py	(.../output_data.py)	(revision 79)
@@ -35,6 +35,7 @@
 
     var_non_gridded = 'non-gridded'
     var_gridded = 'gridded'
+    var_original_scale = 'original_scale'
     var_station_key = 'station'
     var_time_key = 'time'
     var_lat_key = 'lat'
@@ -566,7 +567,7 @@
         #     geo_variable.dtype.str[1:]]
         geo_variable[:] = self.__data_dict[variable_name]
         geo_variable.original_scale = \
-            np.diff(self.__data_dict[variable_name]).mean()
+            abs(np.diff(self.__data_dict[variable_name]).mean())
 
         return geo_variable