An attractive idea, Doug, but I suspect things are more complex. The water
medium seldom has a single temperature with a single associated lag. As we dive
through thermoclines the Dive computer is probably going through different lag
periods dependent on the delta t between computer and water. Furthermore there
are equipment limitations concerning the accuracy of temperature measurements
by dive computers, depending on the thermal mass of the computer and a miriad
of electronic characteristics of the equipment. Dive computers were just not
made for accurate temperature measurements (depending on one's definition of
'accurate'). For serious work, one would need a purpose built water temperature
logger. Then one can define Max and Min temperature in a way it makes sense
within the objectives of the work. Water temp is not an independent and
universal variable. It reflects the complex interaction between environment and
the water medium. To compare two water temperatures is therefore not a trivial
issue. Kind regards, willem.
Sent from Proton Mail mobile
-------- Original Message --------
On 14 Aug 2023, 22:21, Doug Junkins via subsurface wrote:
>> On Aug 14, 2023, at 11:58 AM, Robert Helling via subsurface
>> <subsurface@subsurface-divelog.org> wrote:
>>
>> Matt,
>>
>>> On 14. Aug 2023, at 19:24, Matt Wilbur via subsurface
>>> <subsurface@subsurface-divelog.org> wrote:
>>>
>>> I'm not sure this is a feasible request for mobile subsurface, but on mac I
>>> frequently use subsurface, and I'm also doing surveys on every dive
>>> for[reef.org](http://reef.org/)(I've done about 120 since may). We have to
>>> report max and min temps in our surveys so they can hopefully correlate
>>> temps with the critters and locations we find them in.
>>>
>>> Would it be possible to adjust the "Temp." displayed with the dives in the
>>> dive log and the "Water Temp." in the info display to show a min and max
>>> water temp? So I could just have my dive listing show me my min and max
>>> temps so I don't have to mouse over the dive profile plot to read the max
>>> temp on the dive?
>>>
>>> Whether this is doable or not, thank you SO MUCH for the fantastic open
>>> source dive logging app. I thought I might take a crack at adding a max
>>> temp field to display since the data is all in there - but lost my steam
>>> with the info "Water temp." display possibly needing to be changed too.
>>
>> the problem with this is that the typical temperature sensors on dive
>> computers are very slow. At the start of the dive, the dive computer
>> probably is at the surface air temperature and only slowly (except for dives
>> in mid winter freezing temperatures) cools down to the water temperature.
>> Thus I would not expect that for the first few minutes of the dive, the
>> recorded temperature is actually the ambient water temperature. So what you
>> would be recording as the max temperature is probably much more related to
>> the surface air temperature (which we log if the dive computer reports it).
>>
>> On the other hand, the dive temperature that is shown in the dive list (you
>> realise you can change the fields that are displayed there and their order)
>> is the minimum temperature.
>>
>> At some point, I tried plotting the temperature against depth (rather than
>> against time). I was hoping to see things there like thermoclines but that
>> did not work exactly for the reason of inertia of the temperature sensor.
>
> I was thinking about the lag issue as well. Maybe one way to do it is to cut
> off the first 5-10 minutes of temperature samples before doing the Min/Max
> calculation. It could even be a configuration option for how many minutes of
> temperature samples to ignore in the calculation so people that really want
> this info can customize it based on their own dive computer. Just my $0.02.
>
> -Doug
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