Julian Date format -- interval not dateTime (my thought)

[David Blankman]

Don,

I am not sure what the correct representation of Julian dates would be. 
My sense is that the Julian date scale is actually an INTERVAL scale not 
a dateTIME scale; arithmetic calculations are consistent, that is, 
 2451919 - 2451819 gives the same value as 2351919 - 2351819.  It 
probably also makes sense to say that something that takes 200 julian 
days  = 2 * 100 julian days. My first thought was that it was a ratio 
scale, but it is more like the celcius scale than the kelvin scale in 
that the 0 on the julian scale is an arbitrary one.

The julian date scale does not suffer from the problems that are 
associated with a standard calendar scale, that is, the only unit is the 
day and the fraction of a day; there is nothing like Feb 20 - Jan 20 
representing a different number of days than Aug 20 - July 20.

I would appreciate enl-dev feedback on that.

David

Henshaw, Don wrote:

> David,
> I have reviewed the Andrews unit dictionary.  The following are units 
> of measurement that we have used at the Andrews that I did not find in 
> eml-2.0.0\eml-unitDictionary.xml, as well as a few other notes. 
>  
> Thanks,
> don
>  
> pressure: hectopascal (=100 pascals)
> volume: cubic centimeters
> volumetricArea: cubic meters per hectare               
> volumetricArea: cubic meters per square meter
> massDensity: megagrams per cubic meter
> arealMassDensity: grams per square centimeter
> arealMassDensity: megagrams per hectare
> arealMassDensityRate: grams per square meter per day
> amountOfSubstanceWeight:micromoles per gram
> amountOfSubstanceWeightFlux: micromoles per gram per day
> amountOfSubstanceWeightFlux:micromoles per gram per hour
> amountOfSubstanceWeightFlux:nanomoles per gram per day
> amountOfSubstanceWeightFlux:nanomoles per gram per hour
> speed: inches per hour (used more as a rate than a speed)
> energy?:  megajoule per square meter per day (solar radiation)
> energy?:  langley (1 langley=4.187joules per square centimeter, 41870 
> joules per square meter)
> energy?: langleys per day (solar radiation)
> conductance?: micro mhos per centimeter
>  
> I do not think there are unit types for the following (I assigned unit 
> type names):
> massPerMassRate: micrograms per gram per day
> massPerMassRate:micrograms per gram per hour
> massPerMassRate:micrograms per gram per week
> massPerMassRate:nanograms per gram per hour
> areaPerArea: square meters per hectare
> luminanceRate??: micromoles per square meter per second (light 
> measurement from LICOR instrument)
>  
> Not sure how these fit:
> milliequivalents per 100 grams
> pH units
> ppm (parts per million)
> ppb (parts per billion)
>  
> What about the following use of degrees, minutes, seconds?
> degrees azimuth
> decimal degrees of latitude or longitude
> degrees, minutes, seconds of latitude, longitude
>  
> On another topic:
> Can a julian date be represented in the format string 
> for measurementScale of datetime
> i.e., YYYYddd
>  
> Other notes (being rather picky): pertaining to eml-unitDictionary.xml 
> (2.0.0)
> following units seems to show wrong abbreviation and multiplier
> milliGramsPerMilliLiter
> cubicMicrometersPerGram
>  
> The following unit names seem contrary to the convention of showing 
> units in singular form:
> squareCentimeters
> squareMillimeters
> squareKilometers
> cubicMeterPerKilogram
>  
> Not all units show an abbreviation, even when an obvious one exists, 
> ie., kg/ha or g/g
> liter shows "L" as the abbreviation
>  
>
>     -----Original Message-----
>     *From:* David Blankman [mailto:dblankman at lternet.edu]
>     *Sent:* Monday, February 10, 2003 1:52 PM
>     *To:* Iml
>     *Cc:* Eml-Dev (E-mail)
>     *Subject:* Please review EML unit dictionary
>
>     *Request of LTER IM's *
>     Somehow two units that were supposed to have been in the
>     unitDictionary, numberPerMilliliter and numberPerLiter were
>     mistakenly omitted. Prior to releasing a supplement to the
>     unitDictionary and therefore to EML, we would like to see if there
>     are any other units that we missed.
>
>     In reviewing the unitDictionary, remember that the unit names in
>     the unitDictionary are often more abstract than the ones that you
>     actually use. For example, one of the units that we are in the
>     process of adding is numberPerMilliliter. The "number" portion is
>     an abstract representation of the unit "cells/milliliter".  A unit
>     like microgramsPerGram is an abstract representation of a class of
>     measurements like: micrograms of carbon per gram of soil.
>
>
>-- 
>David E. Blankman
>Database Integration Developer
>Long Term Ecological Research Network Office
>University of New Mexico
>801 University, SE #104
>Albuquerque, NM 87106
>(505) 272-7346 / (505) 272-7080 FAX
>    
>

-- 
David E. Blankman
Database Integration Developer
Long Term Ecological Research Network Office
University of New Mexico
801 University, SE #104
Albuquerque, NM 87106
(505) 272-7346 / (505) 272-7080 FAX

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