nkw5
Contributor
Can someone give me a quick lesson on how to use the PADI Nav-Finder? I thought a quick verbal lesson would stick in mind, but now that I have a NF, I can't remember exactly how to use it. Thanks!
Nav-Finder Basics
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The Nav finder is a simple map maker. The idea is you must first understand your kick cycle or arm length (swing) cycles - or understand HOW to measure distance underwater with reasonable accuracy. You must also understand how to use a compass (track direction). With these two skills combined and the Nav-Finder ... you can correspond the grid with units of measure and rotate the grid to represent direction changes.
To give an illustration imagine you are in an large empty parking lot with a single school bus parked in the dead center. You are trying to navigate a straight line across the lot but the bus blocks your path. Unfortunately visibility is only 10 feet (or less) in the fog and the school bus is 3x longer than the vis and you can't climb over it. This can equate to low vis in the water and a similar reef too high to swim over without surfacing in 15 feet of salt water. Nevertheless your path is critical because your destination is far and you must find the exact destination you are looking for. Therefore, you can use the Nav-Finder to help you plot a course AROUND the bus, record this detour, and once you've completed your journey, use this map again to get back to your point of origin or dive exit.
In the parking lot illustration, you do this by marking the distance and direction you swim with each direction change (a box) as you navigate around the obstacle. With each change of direction you rotate the Nav Finder so you are still indicating your heading with respect to your body position. So you are walking along in the fog and suddenly the bus comes into view dead center of your path. Simply you indicate a course change by "turning right" 90 degrees (using cardinal direction orientation of course) and start noting your distance in paces (under water you'd be counting kick cycles till you reach the edge of the bus), then "turn left" 90 degrees and start a new heading on parallel with your original heading until again you come to another corner of the bus. Again you change direction by turning left again 90 degrees, but this time you travel the exact same distance you made on the first course correction, the one when you first encountered the obstacle, and turned right. When you reach the end of this distance you make your last course correction, right again 90 degrees, and you are now facing the exact same direction and in the same line of the course you started with and the bus is behind you. You may now proceed to your original destination, however with the added burden of counting your paces (or kick cycles).
Bottom line at each turn you rotate the finder and count then mark these lines on the Nav-Finder where the distance is scaled so that a given unit of measure is represented by each square on the grid to be consistent. The beauty of this is you can follow this same map on a reciprocal heading to again swim around the obstacle and safely return you to your dive exit point.
Once you are done with your parking lot swim ... the drawing on the nav finder will, if looked at from a certain angle, appear like a side view line drawing of a hat where the brim represents the line that you intended to swim the bump your head fits into, represents the path around the obstacle, or in this case the bus that was in your way.
This is a simplistic example, but using this technique you can see that even on a reef with a far more complex geography, marking the distance traveled along with directions, will show the necessary course corrections and allow you to navigate in poor visibility to find your way through the trickiest of reef or other obstructions.
To give an illustration imagine you are in an large empty parking lot with a single school bus parked in the dead center. You are trying to navigate a straight line across the lot but the bus blocks your path. Unfortunately visibility is only 10 feet (or less) in the fog and the school bus is 3x longer than the vis and you can't climb over it. This can equate to low vis in the water and a similar reef too high to swim over without surfacing in 15 feet of salt water. Nevertheless your path is critical because your destination is far and you must find the exact destination you are looking for. Therefore, you can use the Nav-Finder to help you plot a course AROUND the bus, record this detour, and once you've completed your journey, use this map again to get back to your point of origin or dive exit.
In the parking lot illustration, you do this by marking the distance and direction you swim with each direction change (a box) as you navigate around the obstacle. With each change of direction you rotate the Nav Finder so you are still indicating your heading with respect to your body position. So you are walking along in the fog and suddenly the bus comes into view dead center of your path. Simply you indicate a course change by "turning right" 90 degrees (using cardinal direction orientation of course) and start noting your distance in paces (under water you'd be counting kick cycles till you reach the edge of the bus), then "turn left" 90 degrees and start a new heading on parallel with your original heading until again you come to another corner of the bus. Again you change direction by turning left again 90 degrees, but this time you travel the exact same distance you made on the first course correction, the one when you first encountered the obstacle, and turned right. When you reach the end of this distance you make your last course correction, right again 90 degrees, and you are now facing the exact same direction and in the same line of the course you started with and the bus is behind you. You may now proceed to your original destination, however with the added burden of counting your paces (or kick cycles).
Bottom line at each turn you rotate the finder and count then mark these lines on the Nav-Finder where the distance is scaled so that a given unit of measure is represented by each square on the grid to be consistent. The beauty of this is you can follow this same map on a reciprocal heading to again swim around the obstacle and safely return you to your dive exit point.
Once you are done with your parking lot swim ... the drawing on the nav finder will, if looked at from a certain angle, appear like a side view line drawing of a hat where the brim represents the line that you intended to swim the bump your head fits into, represents the path around the obstacle, or in this case the bus that was in your way.
This is a simplistic example, but using this technique you can see that even on a reef with a far more complex geography, marking the distance traveled along with directions, will show the necessary course corrections and allow you to navigate in poor visibility to find your way through the trickiest of reef or other obstructions.
tiburon72157
Guest
buoy...nkw might need some aspirin after that, providing he isn't an engineer.
Bah, that's the SIMPLE explanation ... if you throw in a complete lesson with compass use, headings, reciprocals and how to measure distance underwater ... it's too much for a web posting.
OP
nkw5
Contributor
DiverBuoy,
Thanks for taking the time to give me a quick lesson. And yes, I did understand it, although I'm not an engineer. eyebrow However, maybe you can answer a specific question. Do I always hold N of the NF on the top and put in the direction I'm reading in the initial heading box and then draw the line towards the N of the NF?
Thanks for taking the time to give me a quick lesson. And yes, I did understand it, although I'm not an engineer. eyebrow However, maybe you can answer a specific question. Do I always hold N of the NF on the top and put in the direction I'm reading in the initial heading box and then draw the line towards the N of the NF?
That is preferred.
Just like using a compass where you orient the lubber line to your body, in fact your heading is only as accurate as your positioning of the compass to start with, being careful to align the compass with the center line of your body when taking readings or making compass adjustments. When you are navigating with a compass, you twist the bevel ring on the compass BEFORE each physical change in your body's direction such that after your body makes the heading change the compass needle is automatically realigned again with North. In a similar fashion the Nav-Finder grid rotates such that the grid always orients itself the same way.
Just like using a compass where you orient the lubber line to your body, in fact your heading is only as accurate as your positioning of the compass to start with, being careful to align the compass with the center line of your body when taking readings or making compass adjustments. When you are navigating with a compass, you twist the bevel ring on the compass BEFORE each physical change in your body's direction such that after your body makes the heading change the compass needle is automatically realigned again with North. In a similar fashion the Nav-Finder grid rotates such that the grid always orients itself the same way.
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