..... and I thought I was a pedant !!!!!!!!!!!!! most stations with a tipping cup measuring device provide the rain measurements in metric and/or imperial as being measured in units of .3 or .2 mm or .01" per tip - which means there is probably already a rounding error before the floats even begin to have an effect depending on whether the measuring cup was actually manufactured to imperial standards, metric standards or is just somewhere in-between!!!! Davis uses .2, Fineoffset use .3 .......... The implication is that an error of .01" over a month is probably (possibly) insignificant given the likely error in the initial reading anyway!!!!
I limit the digits in my MySQL database by setting the datatype to double(5,2) for rain and rainrate and double(5 or 6,1) for other fields so that I at least do not have to look at masses of decimal digits when viewing the tables with phpmyadmin. I've never checked to see if this beneficial change (to me) affects any calculations though!!! On Sunday, 18 December 2016 07:50:05 UTC+2, Josh Smith wrote: > Sorry if this as been discussed before but after searching through the > discussions I couldn't find one that matches my issue exactly. I noticed > the month rainfall total for my station was off by 0.01". After some > testing, I figured out this was due to the conversion of rainfall data from > mm to inches. The data is stored as a float with 16 significant digits > (i.e. 0.04 is stored as 0.0405511811023656) in the database. Thus, when > using the sum tag like $month.rain.sum, it returns a float with two decimal > place rounded up. So a raw monthly rainfall sum produces 0.3251968503937174 > which becomes 0.33 inch using the $month.rain.sum. I noticed this was an > issue when sending data to Wunderground in 2013 which requires data in US > units.This has been fixed > <https://groups.google.com/forum/#!searchin/weewx-user/US$20conversion$20rain%7Csort:relevance/weewx-user/h7entGBwgRk/WAdYgZldR8QJ>. > > I checked my data on Wunderground and it is reporting the correct amount of > 0.32 inches so I am thinking a similar change needs to be made to the > StdReport. I am running the latest version of WeeWx 3.6.2. Let me know if > you need more info or I missed a fix for this. Thanks. > > -- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to weewx-user+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
