[Auscope-geosciml] Proposed fix for GeologicEvent Numeric age

stephen richard steve.richard at azgs.az.gov
Sat Sep 26 08:40:17 EDT 2009


Thanks for sorting that out more completely Ollie!  Per Simon's 
question, it seems that the UnitOfMeasure element associated with 
Measure (CGI_NumericRange is based on ISO19103 Measure), can be used to 
describe the CRS with origin at 1950, positive older, measured in years?

So the proposal on the table is to change the data type for 
numericAgeDate on GeologicEvent from TM_Period  to CGI_NumericAge.  I'll 
wait til a week monday (Oct 5) for any other discussion, then make the 
change in the v3 trunk.

steve




Oliver.Raymond at ga.gov.au wrote:
> I agree. Time range for events is defined by 2 time positions, not a length of time.  This extract from the Nth American Stratigrapic Code suggests that the units (Ma) for these time positions are positive numbers with units = Ma:
>
> "The age of a stratigraphic unit or the time of a geologic event, as commonly determined by numerical dating or by reference to a calibrated time-scale, may be expressed in years before the present. The unit of time is the modern year as presently recognized worldwide. Recommended (but not mandatory) abbreviations for such ages are SI (International System of Units) multipliers coupled with "a" for annum: ka, Ma, and Ga for kilo-annum (103 years), Mega-annum (106 years), and Giga-annum (109 years), respectively. Use of these terms after the age value follows the convention established in the field of C-14 dating. The "present" refers to 1950 AD, and such qualifiers as "ago" or "before the present" are omitted after the value because measurement of the duration from the present to the past is implicit in the designation. In contrast, the duration of a remote interval of geologic time, as a number of years, should not be expressed by the same symbols. Abbreviations for numbers of years, without reference to the present, are informal (e.g., y or yr for years; my, m.y., or m.yr. for millions of years; and so forth, as preference dictates). For example, boundaries of the Late Cretaceous Epoch currently are calibrated at 63 Ma and 96 Ma, but the interval of time represented by this epoch is 33 m.y."
>
> I had a play with making a CGI_NumericTimeRange element, defined by an upper and lower TM_Coordinate. BUT... there is a mandatory association with TM_CoordinateSystem which involves defining a timescale based on clock and calendar. (See attached picture to see the TM classes involved). Not very applicable to defining the geological time frame.
>
> Another option was to utilise StratigraphicDateEstimate instead of TM_Coordinate, BUT... (i) the same problem with TM_CoordinateSystem arises and (ii) the StratigraphicDateEstimate inherits from TM_Position which allows more than just number age dates. (I think StratigraphicDateEstimate needs re-modelling.)
>
> In summary, given the limitations of TM elements, Steve's proposal to use CGI_NumericRange to deliver numeric age values using the geologic timescale seems to be a good solution.
>
> Cheers, Ollie
>
> -----Original Message-----
> From: auscope-geosciml-bounces at lists.arcs.org.au [mailto:auscope-geosciml-bounces at lists.arcs.org.au <mailto:auscope-geosciml-bounces at lists.arcs.org.au> ] On Behalf Of stephen richard
> Sent: Saturday, 26 September 2009 3:30 AM
> To: Simon Cox
> Cc: auscope-geosciml at lists.arcs.org.au
> Subject: Re: [Auscope-geosciml] boo-boo in GeologicEvent
>
> I think we're talking about position on a timeline, with a CRS set up such that origin is 1950, and positive is older steve
>
> Simon Cox wrote:
>   
>> Yes - TM_Period is about a discrete interval, not uncertainty.
>>
>> There is also the matter of whether 'age' means
>> - position on a timeline, a coordinate
>>    - the conventional origins make this a negative number for most
>> geological events
>> - amount of time embodied in (or 'since') the event, a quantity
>>
>> I.e. interval- vs. ratio-scale.
>>
>> Simon
>>
>>
>> --------------------------------------------------------
>> Simon Cox
>>
>>
>> -----Original Message-----
>> From: auscope-geosciml-bounces at lists.arcs.org.au
>> [mailto:auscope-geosciml-bounces at lists.arcs.org.au <mailto:auscope-geosciml-bounces at lists.arcs.org.au> ] On Behalf Of
>> stephen richard
>> Sent: Friday, 25 September 2009 14:00
>> To: auscope-geosciml at lists.arcs.org.au
>> Subject: [Auscope-geosciml] boo-boo in GeologicEvent
>>
>> There was some uncertainty on my part yesterday as to whether
>> TM_Period is the correct type for numericAgeDate. After studying the
>> ISO 19108 temporalSchema some more, I conclude its not; it only allows
>> a time coordinate specified by a single number, no uncertainty. I
>> recommend we change TM_Period to CGI_NumericRange; this is more
>> consistent with the rest of the model, represents what we want better,
>> and avoids another proxy for a
>> GML3.2 element for v. 3 testing.
>>
>> steve
>> _______________________________________________
>> Auscope-geosciml mailing list
>> Auscope-geosciml at lists.arcs.org.au
>> http://lists.arcs.org.au/cgi-bin/mailman/listinfo/auscope-geosciml <http://lists.arcs.org.au/cgi-bin/mailman/listinfo/auscope-geosciml>
>>
>>     
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