Navigation NAU 102 Lesson 20

From Deduced (ded.) Reckoning Dead Reckoning From Deduced (ded.) Reckoning Abbreviated DR

Dead Reckoning Definition The process of determining present position by projecting course and speed from a known past position. Or, the process of determining future position by projecting course and speed from a known present position.

Dead Reckoning Considers only course and speed. Does not take into account any other factor. Leeway (movement downwind) Current Steering errors Compass error

Determining course of advance Estimated Time of Arrival Dead Reckoning Uses Voyage planning Determining course of advance Speed of advance Estimated Time of Arrival

Approximate location between fixes. Dead Reckoning Uses Keeping track of location in the absence of other positional information. Out of piloting range. Overcast sky. GPS acting up. Approximate location between fixes.

Dead Reckoning Uses Determining outside forces. Wind Current Bad steering If you know the forces, you can compensate for them.

Plan future movements after a fix Compare position to desired location Dead Reckoning Uses Plan future movements after a fix Compare position to desired location DR to determine course and/or speed necessary to regain track or avoid a hazard

Dead Reckoning DR Symbology Use of standard symbols is important Anyone else (Captain/Relief) can instantly understand the situation.

Dead Reckoning Visual fix – circle Electronic fix – triangle GPS fix – diamond Running fix – circle labeled “R-fix R-fix Estimated position – square DR position – half circle

Written horizontally for fixes and EP’s Written diagonally for DR’s Dead Reckoning Times Written horizontally for fixes and EP’s 2000 0812 1932 R-fix 1447 Written diagonally for DR’s 1447

Dead Reckoning Courses Labeled “C” 3 digits True degrees unless otherwise marked Written above the track line Speeds Labeled “S” Written below the track line

Dead Reckoning

Dead Reckoning Rules of DR Plot a DR: 1. At least every hour on the hour 2. After every fix or running fix 3. After every course or speed change 4. After plotting a single line of position (LOP)

Dead Reckoning Constructing a DR Start from a known position (a ‘fix’) Draw a line in the direction of the course (Use True directions only) Calculate the distance to next DR point (using the Rules of DR) Using the mid-latitude, mark off the distance Label!

Dead Reckoning

Dead Reckoning

Between fixes, you may fall off your planned track. Dead Reckoning Departure from Plan Between fixes, you may fall off your planned track. Wind Current Bad steering From your latest fix, DR to regain track and/or avoid navigation hazards.

Dead Reckoning

Dead Reckoning

Dead Reckoning Fix Expansion A DR is an approximation of position based on very limited information. There will always be inaccuracy and positional error in every DR. The longer the time since your last fix, the greater the error.

Dead Reckoning Be extra vigilant when a navigational hazard falls within your error circle.

Alternative format for voyage planning. Dead Reckoning Alternative format for voyage planning. Each turn point (waypoint) is labeled with ETA to the point and distance to destination.

Introduction to Navigation Questions?