Short video on reading charts...

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richg99

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Pretty good. Only thing that I noticed was that he only mentioned degrees, minutes and seconds. A lot of GPS's use the decimal system.

richg99

https://www.youtube.com/watch?v=8w1eUOUpYNM
 
Good video with an overview of the chart. Of course, being a hydro-nerd, I have to comment.

If you're looking for a quick reference on your charts, I'd suggest investing in a copy of Chart No. 1 (https://www.amazon.com/Chart-No-Symbols-Abbreviations-Terms/dp/0939837560/ref=tmm_pap_swatch_0), which is an index of all charting symbols (both paper and electronic) that are used on official NOAA charts.

With respect to the difference between DMS (degrees-minutes-seconds) and decimal degrees; I think that most GPS units have an option to change the display between decimal degrees, degrees and decimal minutes, and DMS. By and large, most charts will have Latitude and Longitude in degrees and decimal minutes (e.g. 74-deg 37.6' N 132-deg 19.9' W), but you will find some very large scale charts with DMS. If you're actually plotting you position, it's worth changing your GPS to match the chart you're using (unless you like multiplying by 6 a lot).

One item that he doesn't discuss that I think is critical to using the chart is the Source Diagram. There's a quick explanation of them with a sample image here on the NOAA website (https://www.nauticalcharts.noaa.gov/mcd/learnnc_sourcediagrams.html). Basically, they will tell you when and how the information was collected for that chart and, in turn, how accurately charted that area is (i.e. how much should you trust the chart to be right). Some areas (particularly in Alaska) are based on data that was collected before 1900 with lead lines.

Another note of caution; the charts are primarily geared towards commercial traffic and while shallow areas are charted, they are often not compiled at the scale to show the detail a small boat might need. 1:40,000 is the best scale you're likely to find outside of a major harbor and at that scale my 14-ft boat wouldn't even show up as a speck of ink (0.0042" long); so that rock symbol scaled up would be over 400-ft in diameter and could be representing anything from a single 3-ft rock to a reef that is 100-ft long to 8-rocks that all fit within that one rock symbol.

Also, if you are plotting positions or measuring distances, I never use the scale; one minute of latitude, which can be pulled off of either side of the chart, is equal to one nautical mile (~1.15-statute miles). Having decimal minutes means that you can get decimal miles as well.
 

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