Setup: Difference between revisions

Setup (view source)

Revision as of 05:13, 2 September 2013

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→‎Units of measure panel: added suggested approach

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 Pay attention to the box labels, enter ''unsigned integers'' for degrees, minutes and seconds, then add either N or S for Latitude and either E or W for longitude.
 === Units of measure panel ===
-By far '''the biggest decision you will make''', and be held to, is the various units of measure.  ''Select these very carefully when you are setting up.''
+By far '''the biggest decision you will make''', and be held to, is the various units of measure.  ''Select these very carefully when you are setting up.''  Remember ''if you try to change your old data later'' it probably has already been rounded and applying a single conversion factor would cause inaccuracy.
-Remember ''if you try to change your old data later'' it probably has already been rounded and applying a single conversion factor would cause inaccuracy.  For instance in rainfall you can't get back exactly to millimetres to 1 decimal place from inches to 2 dp. For example, 0.01 inches is 0.254 millimetres, which rounds to 0.3 mm, but 0.02 inches is 0.508 mm, which rounds to 0.5 mm rather than 0.6.
+'''Conversion tactics''': For instance in rainfall, you can't get back exactly to millimetres to 1 decimal place from inches to 2 dp. To illustrate this, suppose your rainfall gauge has buckets that tip at multiples of 0.3mm but you choose to report in inches.  Then, one tip would report as 0.01 inches, that is 0.254 millimetres, this rounds correctly to 0.3 mm. However, two tips would record as 0.02 inches and applying a simple conversion factor that becomes 0.508 mm, but that rounds to 0.5 mm rather than the 0.6 mm that actually equates to two tips.
-To minimise rounding error, you need to convert the old data first into whatever precision [[:Category:StationSpecific| your weather station]] works in (e.g. Fine Offset rainfall bucket is 0.3mm,  its pressure measurement is in dPa (integer decaPascal), wind speed in tenths of metres/second and temperature in tenths of degrees Celsius), this may be different to how you have set its console display, and then convert into whatever future units you select for Cumulus before rounding. So devising suitable conversion tactics and applying to all old data could require hours of work. See discussions in support forum e.g. [http://sandaysoft.com/forum/viewtopic.php?f=13&t=10216&start=0 this Fine Offset rainfall thread], [http://sandaysoft.com/forum/viewtopic.php?f=6&t=10327&sid=653dc1eceb1c5a0591512b84578680bd this Vantage Vue wind speed thread] or search (specify ''station make'' or ''units you wish to change'') forum.
+To minimise rounding error, you need to:
+#First convert each old observation into whatever precision [[Supported_Devices| your weather station]] works in (e.g. a Fine Offset rainfall bucket is 0.3mm as per illustration above,  its pressure measurement is in dPa (integer decaPascal), wind speed in tenths of metres/second and temperature in tenths of degrees Celsius). You probably have set its console display to different units, but those units are irrelevent.
+#Next convert each figure into whatever future units you now want to use in Cumulus
+#Finally apply rounding.
+So devising suitable conversion tactics and applying to all old observations could require hours of work. See discussions in support forum e.g. [http://sandaysoft.com/forum/viewtopic.php?f=13&t=10216&start=0 this Fine Offset rainfall thread], [http://sandaysoft.com/forum/viewtopic.php?f=6&t=10327&sid=653dc1eceb1c5a0591512b84578680bd this Vantage Vue wind speed thread] or search (specify ''station make'' or ''units you wish to change'') forum.
+'''If you do need to change a unit''', here is a suggested approach:
+#Changing just after a new month has started simplifies the process
+#Exit Cumulus
+#Amend the appropriate parameter line in [[Cumulus.ini#Section:_Station]] to a value representing the new units.
+#Apply conversion tactics (see above) to figures that need to be in the new units in [[yesterday.ini]], [[today.ini]], [[month.ini]], [[year.ini]], [[monthlyalltime.ini]] and [[alltime.ini]].
+#Apply conversion tactics to figures in the (preferably) just started [[Monthly_log_files|current monthly log]].
+#Restart Cumulus
+#This procedure has ensured that all lows and highs can continue to be tracked by Cumulus, while preserving history of past extremes without being affected by change of units (e.g. a new observation of 31 kph is not higher than a past observation of 30 mph).
+#At leisure, use external editor to apply conversion tactics (as derived above) to appropriate observations in past [[Monthly_log_files]] and if appropriate [[Extra_Sensor_Files]].
+# Follow [[Dayfile.txt#Editing_in_Cumulus]] or [[Dayfile.txt#Manipulation_outside_Cumulus]] to apply conversion tactics (as derived above) to appropriate daily summary figures.
 === Further changes to settings ===