[Babase] rain gauge rounding
Jeanne Altmann
altj at Princeton.EDU
Wed Jul 29 13:25:58 EDT 2009
Sorry about not having caught this earlier, but please make it that the
data be in mm as is but that rounding is to nearest single decimal digit
(tenths of a mm). The period of English and of conversion is
historical, very historical and using the original plan involved more
work than seemed worthwhile in this case, but I somehow slipped a mental
cog when agreeing to only integer mm. We do not know for sure the
precision of any particular rain gauge, English or metric, that was used
at some point, but this is a good compromise. Again, I apologize for the
extra effort, am glad that it's caught now.
Unless Susan has other input, please make the change.
jeanne
-----Original Message-----
From: babase-bounces at eeblistserv.princeton.edu
[mailto:babase-bounces at eeblistserv.princeton.edu] On Behalf Of Karl O.
Pinc
Sent: Wednesday, July 29, 2009 12:39 PM
To: The Baboon Database Project
Subject: Re: [Babase] rain gauge rounding
On 07/29/2009 11:10:01 AM, Niki Learn wrote:
> For those out of the loop, we have been wondering why the rain gauge
> data
> (from the handwritten min-max data sheets) is recorded in integers in
> babase
> with no decimal places since this results in a loss of precision and,
> in
> some years, increases annual rainfall by as much as 5mm.
>
As long as we're revisiting this issue again....
As far as the database goes the significant issue is validation,
particularly with respect to values converted from english
to metric. If the value of a measurement taken in 100's
of an inch is 3.1415976 when converted to millimeters,
accurate to 1/100th of an inch, but we want to keep
data read in metric with a precision of a 10th of
a mm then we need different rules regarding how many
decimal places depending on weather the reading was
in english or metric units. This is why the original
design had an indication of the units of measurement
(Inches or mm, or in the case of temperature, F or C)
and the data was to be stored in the original units.
Automatic conversion could then be done to standard
units.
If you're not quite so interested in maximal precision
you can round everything out to a given number of
decimal places after conversion to metric and not
bother storing the original measurement. The only
question then becomes how many decimal places to keep.
Karl <kop at meme.com>
Free Software: "You don't pay back, you pay forward."
-- Robert A. Heinlein
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