On 12/7/2010 9:47 AM, Roy Mendelssohn wrote:
Hi Thomas:
Thanks. Your timing couldn't have been better. There is a lot of discussion in
NOAA right now on how to serve observational data. I am certain this will be
given a good look.
Hi Thomas,
I agree on the spirit of Roy's remark, though not entirely on the
details. It would have been nice if we had had "oceanotron" on our
radar during the UAF meeting a few weeks ago. We did discuss DAPPER,
but not in great detail. So lets open an email discussion how best to
pull the threads (no pun) together.
Our UAF group consensus was to focus on the simpler, non-nested ERDDAP
protocol, (and the ASCII equivalent, as well) rather than the DAPPER
protocol. One straight-forward direction to move from here is to
utilize the ERDDAP system as a gateway from your DAPPER offerings into
the ERDDAP protocol(s). What about the inverse? Can Oceanotron read
the single-level ERDDAP OPeNDAP protocol and re-assemble the 2-level
nesting in order to serve as a gateway into DAPPER? Granted, there are
some inefficiencies in taking this approach, but there are potentially
important interoperability gains.
And of course there are interoperability considerations (and implicit
development tasks) regarding ncStream, as well.
- Steve
=======================
Regards,
-Roy
On Dec 7, 2010, at 9:34 AM, Thomas LOUBRIEU wrote:
Dear Roy, dear all,
We've just published our in-situ data server at Ifremer. It is fully compliant
with what has been done with DAPPER (and Dchart can request our interface).
It disseminates vertical profiles datasets and soon it will disseminate
pointSeries (e.g. mooring datasets) and trajectories (e.g. drifting buoys or
ferry box).
The URL is : http://www.ifremer.fr/oceanotron/OPENDAP/
The request-able criteria are of course, x,y,z,t coordinates and id, but also
feature's metadata (platform code, institution) and phenomenons values (e.g.
temperatures). A session/pagination system is also implemented (with OPeNDAP
indices) to get big data subsets results with several requests each of them not
exceeding a quota.
The software is open-source and can be extended with modules to read datasets
(storage units), to transform datasets (transform unit) and disseminate the
datasets (front-desk). The communication between these modules, especially
observations features, is standardized with Value Objects (their description
is available at :
http://www.ifremer.fr/isi/oceanotron/umlVOReport/oceanotron_uml.html)
You can get the software documentation and source from our wiki :
https://gforge.ifremer.fr/wiki/doku.php?id=oceanotron:start
If you have any question or comment, please do not hesitate to send it.
Best regards,
Thomas
On 12/06/2010 05:53 PM, Roy Mendelssohn wrote:
Agreed. I said similar things at the meeting. But I was starting from the
discussions at the meeting, which was the CDM as implemented in THREDDS. So I
want to get clear in my mind what TDS will be able to do for observational data
first before looking for alternatives.
-Roy
On Dec 2, 2010, at 2:42 PM, Upendra Dadi wrote:
Roy,
With regard WODB, the users want to be able to search not just using physical
coordinates like lat-lon bounding box, but also using other attributes like
institution, project, platform etc which are usually not represented using
coordinate variables. So grouping the data based on physical coordinates might
cause performance issues when searching using other criteria. Would it be
possible to have some additional structures, something like a database index,
but without a full-fledge DBMS? Does TDS allow such structures?
Upendra
Roy Mendelssohn wrote:
Hi John:
Since the UAF meeting in Seattle I have been giving some thought about how to
serve some large, important datasets, such as the raw ICOADS observations or
the WODB observations. While reading over the PointObservation Conventions
proposal on the CF site, while the proposal makes it clear how I might put data
into a netcdf file, it doesn't make clear what the interplay might be with a
service in TDS, and how a possible service might be affected by a very large
dataset without further structure.
So it seems pretty clear that the ICOADS would be points. From the example:
dimensions:
obs = 1234 ;
variables:
double time(obs) ;
time:long_name = "time of measurement" ;
time:units = "days since 1970-01-01 00:00:00" ;
float lon(obs) ;
lon:long_name = "longitude of the observation";
lon:units = "degrees_east";
float lat(obs) ;
lat:long_name = "latitude of the observation" ;
lat:units = "degrees_north" ;
float alt(obs) ;
alt:long_name = "vertical distance above the surface" ;
alt:standard_name = "height" ;
alt:units = "m";
alt:positive = "up";
alt:axis = "Z";
float humidity(obs) ;
humidity:long_name = "specific humidity" ;
humidity:coordinates = "time lat lon alt" ;
float temp(obs) ;
temp:long_name = "temperature" ;
temp:units = "Celsius" ;
temp:coordinates = "time lat lon alt" ;
attributes:
:CF\:featureType = "point";
Now I am assuming that in a TDS implementation of a service, I will be able to
select on the coordinate variables, is that correct? Even so, for something
like ICOADS, obs is quite large and that extract could be quite slow unless
either there is additional structure or the TDS pre-fetches the coordinate
variables much as the present Dapper server does.
Other options would be to say have a file for each 10-degree block, and then
have TDS aggregate over the files - would this be possible. Then the search
would a lot faster when people want time series in a region as opposed to more
synoptic extractions. Would the TDS service be supporting such an option? Or,
as netcdf-4 supports groups, to have 10-degree groups with 2-degree subgroups,
which would work as far as netcdf-4 is concerned, but that is not the same as
TDS knowing what to do with the hierarchy or to take advantage of the structure.
My questions for Profiles (that is for the WODB) are pretty much the same. I
assume that the TDS service will be able to search on the coordinate variables,
is that correct? And I have the issue with the fact that the profile dimension
variable will get quite large and without further structure the search could be
very slow. Adding the same types of structures mentioned above would provide
possible solutions, but only if TDS, as opposed to netcdf4, supported them.
As you may have guessed, these are not theoretical questions - I would really
like to see ICOADS and WODB served as part of the year 2 UAF effort. So now is
a good time to start thinking about how to do it correctly and what the service
will be able to do.
Thoughts?
Thanks,
-Roy
**********************
"The contents of this message do not reflect any position of the U.S. Government or
NOAA."
**********************
Roy Mendelssohn
Supervisory Operations Research Analyst
NOAA/NMFS
Environmental Research Division
Southwest Fisheries Science Center
1352 Lighthouse Avenue
Pacific Grove, CA 93950-2097
e-mail:Roy.Mendelssohn@xxxxxxxx<mailto:Roy.Mendelssohn@xxxxxxxx> (Note new
e-mail address)
voice: (831)-648-9029
fax: (831)-648-8440
www:http://www.pfeg.noaa.gov/
"Old age and treachery will overcome youth and skill."
"From those who have been given much, much will be expected"
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**********************
"The contents of this message do not reflect any position of the U.S. Government or
NOAA."
**********************
Roy Mendelssohn
Supervisory Operations Research Analyst
NOAA/NMFS
Environmental Research Division
Southwest Fisheries Science Center
1352 Lighthouse Avenue
Pacific Grove, CA 93950-2097
e-mail:Roy.Mendelssohn@xxxxxxxx (Note new e-mail address)
voice: (831)-648-9029
fax: (831)-648-8440
www:http://www.pfeg.noaa.gov/
"Old age and treachery will overcome youth and skill."
"From those who have been given much, much will be expected"
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-------------------------------------------------------------
Thomas LOUBRIEU
IFREMER IDM/ISI
BP70
29280 Plouzane
FRANCE
email:Thomas.Loubrieu@xxxxxxxxxx
WWW :http://www.coriolis.eu.org/cdc
Tel.: (+33) (0)2 98 22 48 53
Fax: (+33) (0)2 98 22 46 44
-------------------------------------------------------------
**********************
"The contents of this message do not reflect any position of the U.S. Government or
NOAA."
**********************
Roy Mendelssohn
Supervisory Operations Research Analyst
NOAA/NMFS
Environmental Research Division
Southwest Fisheries Science Center
1352 Lighthouse Avenue
Pacific Grove, CA 93950-2097
e-mail: Roy.Mendelssohn@xxxxxxxx (Note new e-mail address)
voice: (831)-648-9029
fax: (831)-648-8440
www: http://www.pfeg.noaa.gov/
"Old age and treachery will overcome youth and skill."
"From those who have been given much, much will be expected"
