I recall many, many threads on this mailing list that point out that editing salinity isn't really useful. At least when diving with a dive computer you are almost CERTAIN to make things worse by doing so. Your dive computer records pressure, not depth.
I won't try to rehash all of these discussions here, just point out that I wonder if this is a good direction to go. /D > On May 17, 2019, at 4:12 AM, Willem Ferguson > <[email protected]> wrote: > > I have code to make the salinity editable on the Information tab. See > attached two screenshots. The motivation is twofold: > > 1) Frequently the salinity is not provided when logging a dive. There can be > two reasons: > > a) Either the dive computer does not report on salinity or > libdivecomputer does not know how to extract that information. > > b) The dive is entered by hand. > > 2) To make the salinity datum more immediately user friendly. Most users do > not know the density of the water they dive and, in the end, it is treated as > one of the main categories of water: fresh/sea/EN13319. For any user it is > not intuitive to provide a water density. My current code is > backwards-compatible and does not affect the dive or dc structures or the way > any of the calculations are done. > > However, there are few issues to be decided on. > > 1) The density of sea water is not standardised. My Galileo reports a sea > water density of 1025 g/l because this is what the libdivecomputer parser > provides. However, in the rest of the software, as far as I can see, sea > water density is 1030 g/l because that is the value of SEAWATER_SALINITY in > units.h. We should probably move towards more consistency in this. As far as > I can see it does not affect the computations at all but it is not ideal, > especially with data where no explicit water density measurements were taken > but where the dives only indicates a category. > > 2) I am undecided about the utility of EN13319. This is a European standard > for the certification of dive computers, using a water density of 1.0198 for > calibrating dc depth sensors. This standard density is used to make the > calibration of depth sensors across dive computers comparable. I have not > found out why the chose this specific density. The utility of the EN13319 > water density is questionable for divers that log dives after a dive. The > numeric value is pretty close to the density of sea water (some authorities > quote the density of sea water as low as 1.023, less than a half a percent > different from that of EN13319. I do not think that EN13319 is a > halfway-value between sea water and fresh water. Although the use of EN13319 > is likely to be confusing to divers and it clutters the UI, I actually have > no strong opinion on this. > > Kind regards, > > willem > > > > > > > > -- > This message and attachments are subject to a disclaimer. > > Please refer to > http://upnet.up.ac.za/services/it/documentation/docs/004167.pdf > <http://upnet.up.ac.za/services/it/documentation/docs/004167.pdf> for > full details. > _______________________________________________ > subsurface mailing list > [email protected] > http://lists.subsurface-divelog.org/cgi-bin/mailman/listinfo/subsurface
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