Adds only calculation mode.

plot_gps.py

             "{}{}".format(args.pcap_csv_folder, csv),
             dtype=dict(is_retranmission=bool, is_dup_ack=bool),
         )
-        tmp_df["datetime"] = pd.to_datetime(tmp_df["datetime"]) - pd.Timedelta(hours=1)
+        #tmp_df["datetime"] = pd.to_datetime(tmp_df["datetime"]) - pd.Timedelta(hours=1)
+        tmp_df["datetime"] = pd.to_datetime(tmp_df["datetime"])
         tmp_df = tmp_df.set_index("datetime")
         tmp_df.index = pd.to_datetime(tmp_df.index)
         if transmission_df is None:
     parser.add_argument("-l", "--label", help="Label above the plot.")
     parser.add_argument("--no_legend", action="store_false", default=True, help="Do not show legend.")
     parser.add_argument("--save", default=None, help="Location to save pdf file.")
+    parser.add_argument("--time_offset", default=None, type=int, help="Minutes added to GPS datetime.")
+    parser.add_argument("--no_plot", default=False, type=bool, help="Only calculations without plotting.")
 
     parser.add_argument(
         "--show_providerinfo",
     # load dataframe an put it into geopandas
     df = pd.read_csv(args.gps_file)
     df["kmh"] = df["speed (knots)"].apply(lambda x: x * 1.852)
+    if args.time_offset:
+        df["datetime"] = pd.to_datetime(df["datetime"]) + pd.Timedelta(minutes=args.time_offset)
+    else:
+        df["datetime"] = pd.to_datetime(df["datetime"])
     df = df.set_index("datetime")
     df.index = pd.to_datetime(df.index)
 
 
     # read serial csv
     serial_df = pd.read_csv(args.serial_file)
-    serial_df["datetime"] = pd.to_datetime(serial_df["datetime"]) - pd.Timedelta(hours=1)
+    #serial_df["datetime"] = pd.to_datetime(serial_df["datetime"]) - pd.Timedelta(hours=1)
+    serial_df["datetime"] = pd.to_datetime(serial_df["datetime"])
     serial_df = serial_df.set_index("datetime")
     serial_df.index = pd.to_datetime(serial_df.index)
 
         left_index=True,
     )
 
-    print(gdf)
-
-    print("Start plotting...")
     # format to needed format and add basemap as background
     df_wm = gdf.to_crs(epsg=3857)
     #df_wm.to_csv("debug-data.csv")
     # ax2 = df_wm.plot(figsize=(10, 10), alpha=0.5, edgecolor='k')
-    print(df_wm)
+    if args.no_plot:
+        df_wm.to_csv("{}gps_plot.csv".format(args.save))
+        print("Saved calculations to: {}gps_plot.csv".format(args.save))
+        exit(0)
+
+    print("Start plotting...")
+
     ax2 = df_wm.plot()
     ax2 = df_wm.plot(args.column, cmap="hot", legend=args.no_legend, ax=ax2)
     # ax2 = df_wm.plot.scatter(x="longitude", y="latitude", c="kmh", cmap="hot")