EO X51.01 Navigation Theory

•By international agreement chart datum should be low enough that low waters do not fall very far below it

•Regional differences in tidal characteristics lead to different levels of Chart Datum (US vs CAN)

•Lower low water large tide(LLWLT) - Can

Mean lower low water(MLLW) - US

•Depths are measured from lowest water normally observed

•Heights of terrestrial objects are measured from highest water normally observed

• Higher High Water Large Tide(HHWLT) – Canada

 Mean High Water(MHW) - US

•Tide height times are NOT CORRECTED for DST

•For Canada and the USA, if the date you need falls between the 2nd Sunday in March and the 1st Sunday in November, you must correct for DST by ADDING 1 HOUR to the times listed in the table.

Disclaimer: Not every place in the world adjusts their local time for DST. Other nations adjust for DST during different times of the year. Consult the local Sailing Directions and Admiralty list of Radio Signals, Volume 2 to verify.

The next slide shows a Canadian Tide Table

The Reference Port is your location or closest approximate port that the table is created.

The time zone is the local time zone from GMT, there is no DST and you will have to correct

The Month is self explanatory

As described in the preceding videos, this is the values of your high and low tides for the day you have chosen. Using your student work book, complete the exercise questions and find the values on your given tide table. Proceed to the next slide when complete.

The fundamental navigation calculations involve speed, time and distance. If two of these factors are known,

the third can be calculated by using a formula. To remember the correct formula, a speed-time- distance triangle

(as illustrated in the next slide) can be used. When the needed factor is covered up on the triangle, the correct

formula can be pictured.