Navigation - Dead Reckoning (White Board Part 1)

Summary

The video script explains the concept of dead reckoning in navigation, starting with a known position given as a latitude and longitude. It emphasizes the importance of marking the time in military format. The script then details how to plot a course on a chart using a compass and parallel rulers, converting a given compass course to a true course if necessary. It also covers calculating the estimated position (DR) by using speed, time, and distance, and marking it on the chart with a specific symbol. The process involves converting time to a decimal, multiplying speed by time to find distance, and plotting the DR position with a half-moon symbol and the corresponding time.

Takeaways

• 🗺️ Dead reckoning is a method used to estimate one's current position based on a previously known position, course, and speed over time.
• 📍 The starting point is always a known position, which can be obtained through various navigational aids like latitude and longitude coordinates.
• ⏱️ Time is a crucial factor in dead reckoning, with positions and events often recorded in military time for precision.
• 🧭 If given a compass course, it must be converted to a true course before plotting on a chart, ensuring accuracy in navigation.
• 🚢 The course is plotted on the chart using a plotter or parallel rulers, and it's essential to label it with both the course number and speed.
• 📏 Speed is typically provided and is a key variable in calculating the distance traveled over a given time.
• ⏳ To find the estimated position at a future time, perform a distance-speed-time calculation, which involves multiplying speed by time.
• 𑥄 The calculation of time must account for the decimal equivalent, converting minutes into hours for accurate mathematical operations.
• 📐 Use a chart divider to measure the distance traveled and mark it on the chart from the known position.
• 🌙 The symbol for a dead reckoning position is a line with a half-moon, and it's labeled with the estimated time of arrival.
• 🔍 Dead reckoning is a fundamental navigation technique used by the Coast Guard and other maritime services to track and predict positions.

Q & A

What is the starting point for dead reckoning navigation?

The starting point for dead reckoning navigation is a known position, which is typically given as a latitude and longitude position.

How do you determine the known position in dead reckoning?

In Coast Guard exams or practice, a known position is provided, which can be obtained through methods like crossed bearings or radar bearings.

What is the significance of labeling the position with time in dead reckoning?

Labeling the position with time, preferably in military time, is crucial for tracking the progression of the vessel and calculating future positions accurately.

What is the first step after establishing a known position in dead reckoning?

The first step after establishing a known position is to draw a line representing the course on the chart using a plotter or parallel rulers.

How do you handle a course given in compass degrees for dead reckoning?

If a course is given in compass degrees, it needs to be converted to true degrees before plotting on the chart.

What information is typically provided for calculating the DR (Dead Reckoning) position?

For calculating the DR position, you are typically provided with a course, speed, and the time interval since the last known position.

How do you calculate the distance traveled in dead reckoning?

The distance traveled is calculated by multiplying the speed in knots by the time in hours since the last known position.

What symbol is used to represent a DR position on a chart?

A DR position on a chart is represented by a line with a half-moon symbol around it, along with the time标注 at the end of the line.

Why is it important to convert time to a decimal in dead reckoning calculations?

Converting time to a decimal allows for precise calculation of the distance traveled, especially when dealing with minutes and hours.

What is the final step in plotting a DR position on a chart?

The final step is to measure the calculated distance from the known position and mark it on the chart with the DR symbol and time.

How does the script ensure that the dead reckoning process is clear and understandable?

The script provides a step-by-step explanation, including the conversion of degrees, calculating distance, and plotting on the chart, to ensure clarity.