[DDI-ADG] UNC document

[Ilona Einowski]

Dear all (I'm SURE I did "Reply All" this time...)

After another look at this it seems to me that we have discussed most of
these issues.  

I think there needs to be an agreement as to which elements go in which
section of the DDI.  Section 2 (study description and methodology) could
handle some of these elements but as I reread John's Project descriptions it
occurred to me that there are some questions....whether we need to answer
those questions right now is another matter...

We could assume that some of these elements might apply to the entire study.


For example, for "Collection personnel" could we assume you would start and
end the study with the same company or group of surveyors? ...seems logical,
and that would apply to the entire dataset and would belong up in Section
2....

But what about the element "Field collection description/limitations" where
he talks about difficulty getting GPS signal lock due to tree cover or high
buildings...that could vary for these agricultural plots or for the
residential locations...some plots or houses would be easy to lock on,
others would be difficult.  In that case, this element would need to be
associated with each particular plot or residence location.

Same thing with Field collection dates...on a particular study you might be
able to just give the range of dates at the study level but for some
agricultural plots where the survey took place over a period of several days
or weeks, it might be important to know that there was a heavy rain storm on
a particular date which "changed" the appearance of the crops...

I'm sure we can come up with additional wrinkles but this is just to say
that I think what we have already covers most cases...we already aware of
the fact that we needed to build in flexibility.


...just my 2 cents...

Ilona

-----Original Message-----
From: ddi-adg-bounces at icpsr.umich.edu
[mailto:ddi-adg-bounces at icpsr.umich.edu] On Behalf Of Wendy Thomas
Sent: Tuesday, November 08, 2005 1:57 PM
To: ddi-adg at icpsr.umich.edu
Subject: [DDI-ADG] UNC document

After reading this through it does seem like the vast majority of the
information items noted are in the collection methodology section. After
looking at the work that was done by the various working groups and the
content of DDI version 2.0, the SRG concluded that significant work needed
to be done on the structure of items currently in section 2 of the DDI
(study description and methodology). The need for improvement in these
sections touches on all types of data and should be conceptualized and
approached in a unified way. For that reason, major restructuring of this
section (aside from the instrumentation piece) will be scheduled for 3.x.

In fact, it looks like a lot of what they want is already in the DDI but
only as PCDATA buckets. It would be interesting to note what special needs
they have in each area and whether those need to be machine-actionable or
just captured.

That said, the spacial data requirements here are not that complex and
many are not unique to geographic based collection. We have addressed many
of the temporal pieces and the availability of reusable classes on agents
and roles should address some additional points.

The main geographic items are:

1) identifying the type of geography expressed by an observation (point,
line, or polygon)
2) uniquely identifying that within the observation
3) linking it to an appropriate geographic boundary file (if required)

To address each in turn:

1) refer to FGDC/ISO to obtain a controlled vocabulary list of geographic
types (there is also circle and arc that I know of) and provide an element
that allows identification of the most descrete geographic type

2) This can currently be done. A variable (or 2 variables) can be used to
identify the long/lat of a point thereby identifying it uniquely. A line
is simply a start and end point. A polygon is commonly linked to a
geographic file by its identifier (code or name). If you have unique
polygones such as self determined plots, it is best to describe the
polygon using a geography based system (FGDC/ISO etc) providing a unique
identifer to each polygon and then using that identify in the data record
as a link.

3) see 2

or am I missing something in this?

wendy

Wendy L. Thomas                          Phone: +1 612.624.4389
Data Access Core Director		 Fax:   +1 612.626.8375
Minnesota Population Center              Email: wlt at pop.umn.edu
University of Minnesota
50 Willey Hall
225 19th Avenue South
Minneapolis, MN 55455

_______________________________________________
DDI-ADG mailing list
DDI-ADG at icpsr.umich.edu
http://www.icpsr.umich.edu/mailman/listinfo/ddi-adg