diff --git a/doc/grid_decimation.md b/doc/grid_decimation.md
index 1dd8451..66ce58c 100755
--- a/doc/grid_decimation.md
+++ b/doc/grid_decimation.md
@@ -15,8 +15,9 @@ This example transform highest points of classification 5 in classification 9, o
      "file-input.las",
     {
         "type": "filters.gridDecimation",
-		"output_type":"max",
-        "output_name_attribut": "grid"
+	"output_type":"max",
+        "output_name_attribut": "grid",
+	"output_wkt":"file-output.wkt"
     },
     {
           "type":"writers.las",
@@ -34,4 +35,6 @@ Options
 **resolution** :
   The resolution of the cells in meter. [Default: 1.]
 
-**output_name_attribut**: The name of the new attribut. [Default: grid]
\ No newline at end of file
+**output_name_attribut**: The name of the new attribut. [Default: grid]
+
+**output_wkt**: the name of the export grid file as wkt polygon. If none, no export [Default:""]