Applying Notices to Mariners (NTMs)

[r.fairman]

I hope opening a new thread about this subject meets with the forums approval. Aplying NTM's to existing calibrated charts is such a big, and important subject it warrants its own thread.

As a starter here is a general outline of my method of applying NTM's to a NGA chart of Marmaris Turkey

1. Navigate to the NTM for your chart on the NGA Site
2. Copy and paste the complete list of NTM changes into Excel
3. Unmerge all cells
4. Add a row at the top of the table with the appropriate headings Name, Desc latitude, longitude
5. Save the spreadsheet
6. Use GPS Visualizer to convert the Excel file to a gpx file
7. Open the GPX file in OpenCPN
8. The NTM changes are displayed on the chart as waypoints.
9. If you just want to use the GPX file to apply the NTM go though the waypoints and apply the appropriate waypoint symbol
10. If you want to apply the NTM graphically to the chart proceed as below
11. Using imgkap extract a header file and a png file from the chart .kap file
12. Open the png image in program such as photo paint or photoshop and display at 100%
13. Display the calibrated chart in OpenCPN at 100%
14. Use a utility such as Exact Mouse to display the x y coordinates of the mouse pointer
15. In photosop adjust the display to show an area where a ntm change or addition is needed
16. Position the mouse cursor over a distinctive land mark or lat long crossing point and note the x y coodinated of the pointer
17. Alt tab to OpenCPN and position the mouse cursor over the same landmark Drag the chart so that the x y coodinates are the same as the one you noted.
18. Open CPN and Photoshop are now displaying the chart and the image at the same zoom level and same position on the screen
19. Position the mouse cursor over a GPX way point created for the NTM as described earlier
20. Alt tab to Photoshop and the cursor will be at the correct position on the chart image.Note the xy coodinates.
21. You can now open or import an image file for the nav object and place it exactlty at the correct position on the cahrt image
22. Repeat this for all the NTM changes or additions
23. Save the file
24. Convert the png back to a kap file using the header previously created by Imgkap
25. To QA your results open the chart in OpenCPN
26. Display the GPX waypoints and ensure they overlay the nav obeact you have added to the image file
27. With care you an achieve an accurcey of 2.5 meters using this method

This may appear long winded but I applied a 30 point NTM in GPX and the chart image in 1 hour.
This procedure is crying out for automation but that is beyond me I have already suggested a NTM plugin that could use imgkap and imagemagick to do a lot of the tasks

regards

Richard