Support for Introduction to Electronic Chart Navigation


Note 1. To quote from Section 2.9 on Lights

Of frequent interest for navigation in the fog or twilight is the attribute called exhibition condition of light (EXCLIT). This can have values

(1) on 24h a day, called "light shown without change of character",

(2) daytime only,

(3) during restricted visibility only, and

(4) night light, meaning nighttime only. Most lights are night lights, but it can indeed be useful to know if a light is on 24h, ie EXCLIT = 1.

This property is listed in the Light List for some lights, but not many. Generally we have to assume it is night only, unless this is stated otherwise in the Light List. With ENCs, we have a nice place to check this for individual lights. Again, not many are en- coded at present, but this is easy information to know, so hopefully it will be filled in for all lights in the future.

What we forgot to add to the book is the defintion of nighttime. We find this in S-57, Section

Night lights are lights that are normally exhibited from about sunset to about sunrise, they are encoded with EXCLIT = 4 (night light).

Note 2. In passing we recommended downloading NOAA's US Chart No.1 to your phone, but that is not quite so transparent an operation without practice, and it is browser dependent. The problem is the pdf opens up in the browser and not all mobile devices have a way to save it. 

One solution is download it on a computer and then mail it to yourself and the mail program will do the interfacing for you—that is, it will ask how you want to open the attachment. Then choose to open in Kindle or Apple Books. (If you do not have one of those readers, they are all free downloads.) These readers then store it in their resprective libraries, and then you can make your own organized bookmarks and annotations, and it is easy to get to. There are no bookmarks in the original. The graphic index is the last page. With Apple products, Air drop is often an effective way to move files to a mobile device.

Note 3. We have an article online with links to Free ENC Viewers that can be used to read these charts and learn about them.

Note 4. Here are a couple packages of echarts for practice. Each set includes both RNC and ENC. (Pacific Northwest, 23MB) (New England, 12MB)

Note 5. New online course devoted to ENC that uses this book as the text: Electronic Chart Navigation


Internet links referenced in the book that we keep up to date here. If you find a link that does not work, please send notice to [email protected].

1. U.S. Chart No. 1

2. IHO ENC and ECDIS Standards in Force

3. IHO Catalog of International ENC... see also

4. Free ENC Viewers. qtVlm includes a versatile simulator, with live AIS interactions.

5. NOAA nautical chart inquires

6. UKHO H-Notes app for chart and pub discrepancies

7. Wikipedia on AIS. See also Introduction to AIS

8. AIS at USCG Navigation Center (navcen)

9. Caris S-57 Objects and Attributes Online Catalog

10. NMEA Revealed

11. IMO Documents (linked from USCG)

12. S-57 Appendix A, IHO Object catalog

13. Reserved

14. Air gap system for live air draft

15. Value of NOAA PORTS services

16. Accuracy of NOAA chart data

17. Starpath Pocket Navigation Rules Handbook

18. World Magnetic Model and geomag software

19. NZ ENC Guidelines

20. U.S. Coast Pilot

21. Bowditch, American Practical Navigator, NGA Pub. 9

23. S-66 Facts about ENC

24. High Resolution Rapid Refresh (HRRR) model and others described at

25. Grib files for meteorology and oceanography (Saildocs)

26. Download NOAA Charts and access Online ENC Viewer... see also

27. MACHC online ENC viewer

28. Free Inland ENCs

29. NOAA Custom Chart descriptions and app links

30. Printing NOAA Custom Charts (NCC)

31. NOAA Rescheming Program with links to program status

32. Implementing the National Charting Plan