Bottom Time vs Total Duration

[Nick Barter]

I've noticed an occasional difference between the dive time my GEO 2 gives me and the total elapsed time MacDive calculates:

-MacDive appears to calculate dive time as the period between the first and last sample.

-My computer ignores any time at the surface (<2m) during a dive, e.g. on training dives with surface time, surfacing in caves, etc.

E.g. on a recent dive to Cathedral Cave in Gozo we spent 7 minutes inside the cave on the surface. The computer gives a dive time of 44 mins. MacDive calculates 51 mins (from 3060 seconds with 15 second sample rate).

I wouldn't bet my house on this but I think the way the computer handles it is closer to a diver's understanding of bottom time. I'd be interested to hear your views. I can see arguments both ways, e.g. after 7 minutes on the surface you are really starting a second dive with minimal surface interval (I believe my computer would register a second dive if more than 10 minutes was spent on the surface).

The main reason I would like a Dive Time Calculation that matches my computer is I use the computer stats after a dive for a paper log and for the Dive Marshall. My paper log is now out of sync with my MacDive log and the difference is growing. Any chance of a 'bottom time' type dive time as well as an overall elapsed time?

[nick]

This is correct, as some computers don't record a bottom time. It's done this way for consistency.

I can look at adding a further bottom time as specified by the computer, but in a lot of places it is better to use the actual duration.

[Nick Barter]

That would be great to see at some point. I think the GEO2 just ignores any sample where the depth is recorded as zero.

Love the programme.

thanks

Nick

[nakatomi]

As far as I can tell, the bottom time in MacDive also includes time spent at the surface.

This affects the AMV calculation since usually, once at the surface, one would most likely not breathe through the regulator.

Maybe it would make sense tweak this?

- Cut out the time spent at the surface (e.g above 0.5 meters) from the total bottom time
and
- Remove this surface time from AMV and average depth calculations

Oliver

[Jean-Francois]

I dove yesterday and my dive lasted 59 minutes on my OSTC and when I downloaded the dive in Mac dive, it recorded it at 63 minutes. I was wondering where the discrepancy came from ?
Just for a test I downloaded the exact same dive in JDivelog (I use it to upgrade the firmware on my OSTC) and 59 minutes was recorded.
Not a big deal really, I just wanted to understand why there was a difference in Mac-dive and not JDiveLog.

[nick]

Read this thread and others - Macdive records the total duration not the bottom time specified by the dive computer. Other software does this its own way.

[Jean-Francois]

Would it be possible to have a choice under preference wether you'd like bottom time or total duration ? or maybe it's too much work for what it would be worth (I don't know anything about programing so I have no clue how hard/easy it would)
Again it's no biggie.