diff --git a/Inst_eddies/Analysis/plot_velocity.py b/Inst_eddies/Analysis/plot_velocity.py
index b7085b178cd1376def932e0ff3694fa22d214a6e..9e0d5c4fb4eedb8d9029ecf920db8055b1d5cbc2 100755
--- a/Inst_eddies/Analysis/plot_velocity.py
+++ b/Inst_eddies/Analysis/plot_velocity.py
@@ -16,6 +16,8 @@ parser.add_argument("-w", "--window", help = "choose a limited plot window",
                                "urcrnrlat"))
 parser.add_argument("--save", metavar = "format",
                     help = "Save file to specified format")
+parser.add_argument("-u", "--undefined", action = "store_true",
+                    help = "plot points where velocity is not defined")
 args = parser.parse_args()
 
 with netCDF4.Dataset("h.nc") as f:
@@ -52,15 +54,23 @@ projection = ccrs.PlateCarree()
 ax = plt.axes(projection = projection)
 
 with netCDF4.Dataset("uv.nc") as f:
-    quiver_return = ax.quiver(longitude[lon_mask],
-                              latitude[lat_mask],
-                              f["ugos"][0, lat_mask][:, lon_mask],
-                              f["vgos"][0, lat_mask][:, lon_mask],
-                              scale = args.scale,
-                              scale_units = "width",
-                              transform = src_crs)
-plt.quiverkey(quiver_return, 0.9, 0.9, 1, r"1 m s$^{-1}$",
-              coordinates = "figure")
+    if args.undefined:
+        undef_velocity = np.logical_or(f["ugos"][0].mask, f["vgos"][0].mask)
+        lon_2d, lat_2d = np.meshgrid(longitude[lon_mask],
+                                     latitude[lat_mask])
+        ax.plot(lon_2d[undef_velocity].reshape(-1),
+                lat_2d[undef_velocity].reshape(-1), transform = src_crs,
+                marker = "*", color = "violet", linestyle = "None")
+    else:
+        quiver_return = ax.quiver(longitude[lon_mask],
+                                  latitude[lat_mask],
+                                  f["ugos"][0, lat_mask][:, lon_mask],
+                                  f["vgos"][0, lat_mask][:, lon_mask],
+                                  scale = args.scale,
+                                  scale_units = "width",
+                                  transform = src_crs)
+        plt.quiverkey(quiver_return, 0.9, 0.9, 1, r"1 m s$^{-1}$",
+                      coordinates = "figure")
 
 ax.gridlines(draw_labels = True)
 ax.coastlines()