Fixing a Position Flashcards
How many arrows does a transferred position line get?
Two on each end.
How can you estimate leeway?
Compare the angle of the wake to your heading.
How many arrows does a tide line have?
3
If you are close-hauled or reaching in winds up to an F4, how much leeway should you use?
5 degrees
How many arrows does a water track have?
1
How do you do a Running Fix?
- Take a bearing on the charted mark.
- Draw line from charted mark out and note the time and log (AB). Put arrows on each end because it’s a position line.
- After an hour, take a bearing on the charted mark again and note the time and log (BC).
- Using anywhere on line AB, plot your course steered and length using your log readings.
- Add the effect of the tide to that line.
- From the end of the tide line, make a line from it to line BC that is parallel to line AB. Where it intersects is your position.
Mark it with a dot in a circle with the time.
How can you use a charted mark and a depth sounding to determine where you are?
Take the bearing of a charted mark.
Use the depth sounding to determine where you are on the map. Best if you can position yourself on a contour.
Be sure you include the height of tide in the total depth.
If you can take a bearing of a second charted mark, you have a good fix.
Name 8 ways to fix your position.
- Come along side a charted mark = Good
- Single point fix & depth = Average
- Two point fix & depth = Good
- Three point fix = BEST
- Transit and cross bearing = Good
- Radar range = Average
- Sector light and depth = Average
- Doubling the angle on the bow = Poor
How many arrows does a position line get?
One on each end
What is a Running Fix?
It’s a fix we determine by using one charted mark.
How do you calculate your Estimated Position?
- Covert magnetic course to true.
- If wind is on the port side, add leeway to course. If wind is on the starboard side, subtract leeway from course.
- Plot your course with one arrow for your water track. Use your log to see how far you’ve traveled within the past hour to know low long the line should be.
- Calculate the direction and speed of the tide. Add the line with 3 arrows to where your left off on #3.
- Mark the end of this line with a dot and triangle. This is your estimated position.
- If you join the start position to the EP, this is the course over the ground track and should be marked with 2 arrows. This is your COURSE OVER THE GROUND (COG).
- Measure the length of the COG. This is your SPEED OVER THE GROUND.
If you are close-hauled or reaching in winds more than an F4, how much leeway should you use?
10 degrees
How do you take a 3 point fix?
Take a bearing on 3 charted marks, ideally spread evenly.
TAKE THE BEARING OF THE MARK ABEAM LAST!
Where they cross is where you are.
Odds are that the lines won’t meet at a single point. They will instead create a “cocked hat” (triangle). You are somewhere in that cocked hat.
If the wind is on your starboard, should you add or subtract your leeway to determine your estimated position (EP)?
Subtract the leeway
What is a sector light fix?
When you use where a lighthouse light changes color and the depth sounding to determine where you are.
If the wind is on your port, should you add or subtract your leeway to determine your estimated position (EP)?
Add the leeway
What is an Estimated Position (EP)?
It’s the position you estimated you are after you’ve traveled from a known position.
What is Dead Reckoning (DR)?
The position obtained from the true course steered and the speed through the water (log). Does NOT include allowances for leeway or tide.
If the wind is on your port, should you add or subtract your leeway to determine your course to steer (CTS)?
Subtract the leeway from your CTS
How do you mark a fix on the chart?
A dot with a circle around it and the time the fix was taken
Mark the bearing lines with arrows on one end
Erase the bearing lines except for the parts right around the bearing.
How can you use a charted mark to determine your fix?
Come along side it and use the map to get the coordinates. Good way to get your fix.
What is Doubling the Angle on the Bow?
Take a bearing on a charted mark. Make note of your log reading.
When the charted mark bearing becomes 2x’s the original bearing, make note of your log reading.
Plotting these will show an isosceles triangle. The difference between the two log readings gives you the distance of two sides of the triangle.
USE WITH CAUTION because this does not include leeway or tidal data!
REALLY ONLY USED AT NIGHT WHEN THERE IS ONLY ONE CHARTED MARK TO USE
How many arrows does a ground track have?
2
If the wind is on your starboard, should you add or subtract your leeway to determine your course to steer (CTS)?
Add the leeway to your CTS
How can you use a transit to determine your position?
Sail down a transit bearing.
Look for another charted mark. When it is 90 degrees to your bearing, you mark it on the chart.
