[Babase] rain gauge rounding

Niki Learn nlearn at princeton.edu
Wed Jul 29 12:10:01 EDT 2009


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.

 

I have been looking through the babase list archives to see where this
decision might have come from.  So far I have found the following but do not
yet understand where the assumption that the rain data in mm is supposed to
be an integer value came from -  the data is in fact entered with one
decimal place (looking at Tabby's data file it looks like we started using
mm in the middle of 1984; thereafter there is only one nonzero decimal
entered).  

 

Beyond that it seems that it was decided only to round the data that was
converted from inches, which had previously had two decimal places included.
It seems that this decision was based partly on the assumption that rain
data in mm was recorded as an integer (this is only true of weatherhawk rain
data!).  I will look farther back and see if I can find earlier references
to the rain gauge being read only in whole integers but it seems to me at
this point like there should be one decimal throughout the dataset
(including for inches to match mm.unless the old rain gauges in inches were
really not as precise or something?).

 

Niki

 

kfenn kfenn at princeton.edu
<mailto:babase%40www.eco.princeton.edu?Subject=%5BBabase%5D%20Rain%20units%2
0and%20other%20weather%20leftovers&In-Reply-To=1238127564l.30163l.4l%40mofo>

Fri Mar 27 15:26:50 EDT 2009 

  _____  

Karl O. Pinc wrote:

> Note that RAINGAUGES.Rain is (supposedly) an

> integral number of millimeters, no decimal point allowed.

> If we really need fractions of a millimeter then

> the original measurement was probably in inches

> and was converted.  In that case we could consider

> doing for the rain units what was originally designed

> for the temperature measurements, store the

> value as read, have another column

> for the units, and have a function/view that automatically

> converts the units and makes them consistent.

> 

I see what you are saying.  I looked up one decimal values (21.84 on 

23/2/77)  The values were recorded in inches on our hard copies.  Jeanne 

should say how she wants to deal with the decimal resulting from these 

conversions.

 

Karl O. Pinc kop at meme.com
<mailto:babase%40www.eco.princeton.edu?Subject=%5BBabase%5D%20Rain%20units%2
0and%20other%20weather%20leftovers&In-Reply-To=D6A894F6502BDF43AF0C4A59BB974
04F03B1DB3F%40EXCLUSTER.pu.win.princeton.edu> 
Sat Mar 28 13:47:21 EDT 2009

On 03/27/2009 04:19:43 PM, Jeanne Altmann wrote:
> Thanks Karl.  As you know, Tabby won't be back until Tuesday.
> However,
> if you need me to try to handle something before then, alert me.  :-)
 
I don't need you to handle it, but you're probably the one who's
going to handle it anyway.  "It" being the question of
the fractional millimeters of rain measurement that are
currently present in the data.  (There's 2 decimal points
of precision (1/100th of a mm!) in the data Tabby sent.)
See the thread:
 
Subject: [Babase] Rain units and other weather leftovers
On 03/26/2009 11:19:24 PM, Karl O. Pinc wrote:
 
> Note that RAINGAUGES.Rain is (supposedly) an
> integral number of millimeters, no decimal point allowed.
> If we really need fractions of a millimeter then
> the original measurement was probably in inches
> and was converted.  In that case we could consider
> doing for the rain units what was originally designed
> for the temperature measurements, store the
> value as read, have another column
> for the units, and have a function/view that automatically
> converts the units and makes them consistent.
 
Or we just do something like round the data to the
nearest even mm.
 
Karl <kop at meme.com <http://www.eco.princeton.edu/mailman/listinfo/babase>
>
Free Software:  "You don't pay back, you pay forward."
                  -- Robert A. Heinlein

 

 

Jeanne Altmann altj at Princeton.EDU
<mailto:babase%40www.eco.princeton.edu?Subject=%5BBabase%5D%20Rain%20units%2
0and%20other%20weather%20leftovers&In-Reply-To=1238262441l.17575l.0l%40mofo>

Sat Mar 28 14:42:26 EDT 2009 

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  _____  

Susan, I would say round to the nearest mm for the records that have

decimal values from inches conversion; your thoughts? 

 

 

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