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How to compare dives?

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jvoets

New Member
Sep 4, 2001
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I'm playing around with the divelog from my suunto stinger.
Each record in this logfile contains Average Depth for that dive and the total time of the dive.

For the fun of it, I'm comparing dives based on the product of these 2 numbers. Now I'm wondering of this is a valid way of determining which dive was 'tougher'.

Is 60 seconds at an average depth of 10 meters (60 * 10 = 600)
a better achievement than 30 second dive with 15 meters average (30 * 15 = 450)?

Any thoughts on this?
 

jvoets

New Member
Sep 4, 2001
180
19
0
48
Still playing around with the dive profiles
Your remark on the derivative of the profile made me think about fitting a theoretical curve.
Did you ever do something like that? Most of my dives look pretty similar, almost parabolic shaped. Would be interesting to find out your 'personal dive profile' parameters.
The dive speed & the area under the profile would follow directly from such a formula .
 

jvoets

New Member
Sep 4, 2001
180
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48
I just found a great tool Advanced Grapher that could do a best fit of one of my profiles. The best one is 9th order polynomial. I settled for a 5th order.

Turns out that my dive followed this formula (x being time in seconds and y the depth in meters):

y= 8.6 *10^-8 * x^5 - 1.9 * 10^-5 * x^4 + 1.5 * 10^-3 * x^3 - 4.1 * 10^-2 * x^2 - 0.19 *x -0.93

Better to see the graphs themselves .

Interesting to see the almost constant ascent rate in the 50-70 second interval and then the sudden acceleration of it towards the end of the dive :duh
 
Last edited:

jvoets

New Member
Sep 4, 2001
180
19
0
48
I made an ASCII export from the Dive Manager software. This will give you 4 CSV files. For example calling the export 'divelog' results in:

divelog.csv -> most of the information per dive
divelog$DGE.csv -> the gear you added for a dive
divelog$NOT.csv -> the notes you added for a dive
divelog$PRO.csv -> dive profiles!!!

this last one contains rows with:
dive number, measurement number, depth, a lot of bogus ....

I extracted the profile for this graph from this last file copied the numbers into the grapher program and let it fit.
A lot of my profiles look like a steep descent parabola on the left and a broader (slow ascent) parabola glued to it on the right.

I was just rethinking the derivative. In it's simplest form it should be a straight line going through y=0 at your max depth point. Or 2 straight lines with a slightly different angle that connect in that point. The graph from this fit might be too fancy due to the 5th order polynomial coming out of the fit.
 
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