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SAC rate calculation problem (?)

Posted: Tue Aug 05, 2014 12:33 am
by msevestre
Hi

I'm getting some strange results on my two last dives.

Compared to previous ones, the difference comes from the fact that I created them under DiveLog & synced them with MacDive.

The problem is that the SAC rate displayed in Gases tab is OK, but the overall SAC rate displayed is more than double.

Note: the dive is with a single 15l tank, as usual.

A clue ? (see enclosed XML export)

Matt

Re: SAC rate calculation problem (?)

Posted: Tue Aug 05, 2014 4:03 am
by nick
The average depth of your dive is 0.0, so the calculation will be thrown off, while the tank-specific one will be correct.

In the case of one mix/tank, MacDive will calculate based on the main dives average depth as a performance optimisation, rather than counting the individual samples. Whereas in the gas tab, they are always calculated.

So - fix the invalid average depth and the SAC should be as you expect.

Cheers

Re: SAC rate calculation problem (?)

Posted: Tue Aug 05, 2014 4:52 am
by msevestre
Hi

Thanks for the analysis

Isn't the average depth estimated by macdive using the dive profile ?

The data seems correctly calculated on divelog side so that's curious that it is not sent during sync to macdive... No ?

Matt

Re: SAC rate calculation problem (?)

Posted: Tue Aug 05, 2014 5:01 am
by nick
MacDive calculates the average depth when a dive is imported from a device or filetype.

I'm not sure why it wasn't sent from Dive Log. What did the summary say for that particular dive? Did it choose the Dive Log or MacDive value? Either way, you can manually fix it and your issue is resolved.

Thanks.

Re: SAC rate calculation problem (?)

Posted: Tue Aug 05, 2014 5:07 am
by msevestre
The average is displayed on DiveLog side.

I may see with Greg about this.

Re: SAC rate calculation problem (?)

Posted: Tue Aug 05, 2014 5:35 am
by nick
As far as I recall, Dive Log does not calculate it on the fly. However maybe it does if no average depth is specified. Either way, you can fix this by simply specifying the average depth.

Thanks

Re: SAC rate calculation problem (?)

Posted: Tue Aug 05, 2014 1:41 pm
by msevestre
Hi

Divelog calculates it on the fly and does not sync this data

Macdive may calculate this information for a created dive on divelog synced with macdive from my point of view considering it is not synced, no ?

Matt

Re: SAC rate calculation problem (?)

Posted: Tue Aug 05, 2014 1:56 pm
by nick
Ok.

Re: SAC rate calculation problem (?)

Posted: Tue Aug 05, 2014 2:12 pm
by msevestre
Hi
Thanks taking this into account

In fact previously, there were rather no dives created from divelog I guess. A lot of people were doing like me : import dives from macdive then sync with divelog... This way, the lack of average depth was never met.

Now that devices such as DCbuddy (I'm using it and helping on divelog side (I'd be happy to help for macdive if needed)) exists, new dives can easily created from divelog and synced to macdive in a second step, creating a new workflow and making appear the average depth drawback.

Matt

Re: SAC rate calculation problem (?)

Posted: Tue Aug 05, 2014 2:41 pm
by nick
I see. You're using an unreleased version that has different behaviour in this case, from the current Dive Log. It sounds like you've found a bug. I've not had any beta versions or contact from Greg on this matter, so I think you need to get him to address it on the Dive Log side.

Greg is very good about contacting me when things are changing, so that we can ensure they work smoothly. Given this behaviour is different, I expect he just forgot to store it, even if only for compatibility.

Certainly MacDive doesn't make any promises about supporting unreleased versions of Dive Log, as I said I'd expect to hear from Greg if there were actual changes like this being planned. I'm sure he can fix up the Dive Log side easily for you.

Thanks!