Salinity vs. density of water

[Willem Ferguson]

Robert I would suggest let the user select either sea water or fresh
water.  I know of no dive computer that does not have only those two
options. For planning purposes keep the density as you have it but please
get the terminology right: density means g/ml or kg/l which is the same
number. Salinity means g of salt per litre of water. And even then the
concept of 'salt'  is vague. Definitely not only NaCl. I doubt if divers
really worry about that.
Kind regards,  willem
On 26 Feb 2016 2:45 PM, "Robert Helling" <helling at lmu.de> wrote:

> Hi,
>
> for those of you who do not follow the discussion in the google forum:
>
> A user reported a wrongly calculated SAC in
> https://groups.google.com/d/msgid/subsurface-divelog/583da598-2554-4309-9387-a150e47997fd%40googlegroups.com
> <https://groups.google.com/d/msgid/subsurface-divelog/583da598-2554-4309-9387-a150e47997fd%40googlegroups.com?utm_medium=email&utm_source=footer> and
> I could track it down to a line in the xml file that specifies the salinity
> to 35g/l. But salinity value in subsurface is actually treated as the
> density of water (in the conversion of depth to ambient pressure) and the
> UI only displays this value but there is no way to set it manually (outside
> the planner). So my guess is it came from the dive computer which happens
> to be an Oceanic Oci 279.
>
> My question is: what is the semantic of the salinity in libdivecomputer,
> is it “just the mass of salt per liter of water” (in which case we would
> need to change the translation in subsurface) or is it like in subsurface
> the density of water (i.e. mass of water plus salt per liter)? In the
> latter case, there needs to be a conversion when reading out this oceanic
> computer.
>
> Best
> Robert
>
> --
>
> .oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oOo.oO
> Robert C. Helling     Elite Master Course Theoretical and Mathematical
> Physics
>                       Scientific Coordinator
>                       Ludwig Maximilians Universitaet Muenchen, Dept.
> Physik
>                       Phone: +49 89 2180-4523  Theresienstr. 39, rm. B339
>                       http://www.atdotde.de
>
> Enhance your privacy, use cryptography! My PGP keys have fingerprints
> A9D1 A01D 13A5 31FA 6515  BB44 0820 367C 36BC 0C1D    and
> DCED 37B6 251C 7861 270D  5613 95C7 9D32 9A8D 9B8F
>
>
>
>
>
>
> _______________________________________________
> subsurface mailing list
> subsurface at subsurface-divelog.org
> http://lists.subsurface-divelog.org/cgi-bin/mailman/listinfo/subsurface
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.subsurface-divelog.org/pipermail/subsurface/attachments/20160226/c5807ea4/attachment.html>