Hi Rich,
...
>
> Denis -- It seems that you are doing something slightly different than
> ESRI. Are you using ESRI WKT, OpenGIS WKT in your NetCDF files, or
> something different. It would be nice to see an example of these as
> well. Is your primary objective to have a NetCDF file that can be used
> as input and output from GDAL, but able to handle any georeferencing
> information that GDAL is capable of producing?
My primery objective is indeed to have a NetCDF file that can be used as
input and ouput from GDAL. And I want the NetCDF driver to handle any
georeferencing information that GDAL is capable of producing.
I am using OpenGIS WKT in my NetCDF files. I can easily support ESRI PE
strings, but I do not know at this point if ESRI PE strings is equivalent to
ESRI WKT. Here is an example of GDAL NetCDF file. It is still a prototype
at this point and needs to be polished.
I used NetCDF CF-1 convention to create the file.
netcdf CratedNetcdf {
dimensions:
x = 515 ;
y = 515 ;
variables:
char lambert_conformal_conic ;
lambert_conformal_conic:Northernmost_Northing =
15448.6987687312
;
lambert_conformal_conic:Southernmost_Northing = -
15451.301231268
8 ;
lambert_conformal_conic:Easternmost_Easting =
15488.384688517 ;
lambert_conformal_conic:Westernmost_Easting = -
15411.615311483 ;
lambert_conformal_conic:spatial_ref = "PROJCS[\"LCC
E000
\",GEOGCS[\"NAD27\",DATUM[\"North_American_Datum_1927\",SPHEROID[\"Clarke
1866\",6378206.4,294.9786982139006
,AUTHORITY[\"EPSG\",\"7008\"]],AUTHORITY[\"EPSG\",\"6267\"]],PRIMEM[\"Greenwich\",0],UNIT[\"degree\",
0.0174532925199433],AUTHORITY[\
"EPSG\",\"4267\"]],PROJECTION[\"Lambert_Conformal_Conic_2SP\"],PARAMETER[\"standard_parallel_1\",
33.90363402777778],PARAMETER[\"standard_parallel_2\",33.6252900
2777778],PARAMETER[\"latitude_of_origin\",33.76446202777778
],PARAMETER[\"central_meridian\",-117.4745428888889
],PARAMETER[\"false_easting\",0],PARAMETER[\"false
_northing\",0],UNIT[\"metre\",1,AUTHORITY[\"EPSG\",\"9001\"]]]" ;
lambert_conformal_conic:GeoTransform = "-15411.6 60 0
15448.70-60 " ;
lambert_conformal_conic:grid_mapping_name =
"lambert_conformal_conic" ;
lambert_conformal_conic:standard_parallel_1 = 33.90363f ;
lambert_conformal_conic:standard_parallel_2 = 33.62529f ;
lambert_conformal_conic:latitude_of_projection_origin =
33.76446f ;
lambert_conformal_conic:central_meridian = -117.4745f ;
lambert_conformal_conic:false_easting = 0.f ;
lambert_conformal_conic:false_northing = 0.f ;
byte Band1(y, x) ;
Band1:coordinates = "lon lat" ;
Band1:grid_mapping = "lambert_conformal_conic" ;
Band1:long_name = "GDAL Band Number 1" ;
Band1:_FillValue = -9999. ;
// global attributes:
:Conventions = "CF-1.0" ;
:AREA_OR_POINT = "Area" ;
}
> John -- how does this stuff relate to Unidata's "Coordinate System
> Object Model"?
>
> Thanks,
>
> -Rich
>
> --
> Richard P. Signell
> U.S. Geological Survey Phone: (508) 457-2229
> 384 Woods Hole Road Fax: (508) 457-2310
> Woods Hole, MA 02543-1598
>
>
>
> Denis Nadeau wrote:
> > Steve,
> >
> > I have finished the projection part of NetCDF with the same approach.
> > It is not checked in yet, but I am planning to do so today. I have
> > created and computed the following metadata.
> >
> > Attributes:
> > Northernmost_Northing (These attributes are used only if there is no
> > GeoTransform array.)
> > Southernmost_Northing
> > Easternmost_Easting
> > Westernmost_Easting
> >
> > GeoTransform (this is the GDAL adfGeoTransform array )
> >
> > spatial_ref (this is the WKT you called esri_pe_string );
> >
> > Denis
> >
> > 2006/4/28, Steve Kopp <skopp at esri.com <mailto:skopp at esri.com>>:
> >
> > Denis,
> >
> >
> >
> > After discussions with John last year, this is the same approach we
> > have taken with ArcGIS when exporting to netCDF, and so far it is
> > working well for us.
> >
> >
> >
> > When we export to a netCDF file we write projection information as
> > an attribute of a variable. We call the attribute "esri_pe_string".
> > Of course we are reading and writing the CF standard projection
> > information when it is a coordinate system supported by CF.
> >
> >
> >
> > Steve
> >
> >
> >
> > float wdemclputm(y, x) ;
> >
> > wdemclputm:long_name = "wdemclputm" ;
> >
> > wdemclputm:esri_pe_string =
> >
> "PROJCS[\"Clarke_1866_UTM_Zone_12N\",GEOGCS[\"GCS_Clarke_1866\",DATUM[\"D_Clarke_1866\",SPHEROID[\"Clarke_1866\",
> 6378206.4,294.9786982]],PRIMEM[\"Greenwich\",0.0],UNIT[\"Degree\",
> > 0.0174532925199433
> ]],PROJECTION[\"Transverse_Mercator\"],PARAMETER[\"False_Easting\",
> 500000.0],PARAMETER[\"False_Northing\",0.0
> ],PARAMETER[\"Central_Meridian\",-111.0],PARAMETER[\"Scale_Factor\",
> > 0.9996],PARAMETER[\"Latitude_Of_Origin\",0.0],UNIT[\"Meter\",1.0]]"
> ;
> >
> >
> >
> >
> >
> >
> ------------------------------------------------------------------------
> >
> > *From:* owner-galeon at unidata.ucar.edu
> > <mailto:owner-galeon at unidata.ucar.edu> [mailto:
> > owner-galeon at unidata.ucar.edu
> > <mailto:owner-galeon at unidata.ucar.edu>] *On Behalf Of *Denis Nadeau
> > *Sent:* Thursday, April 27, 2006 6:51 AM
> > *To:* John Caron
> > *Cc:* galeon at unidata.ucar.edu <mailto:galeon at unidata.ucar.edu>; CF
> > *Subject:* Re: GDAL NetCDF driver and projection.
> >
> >
> >
> > Hi John,
> >
> > Thank you for taking the time to write this email. Your points are
> > very clear, and they are very helpful. I must tell you that you
> > give me information and that you sure taught me about CF-1
> > convention community . I will keep your email as a reference when
> > coding the GDAL NetCDF driver.
> >
> > I have decided to use WKT to encode projections and if I see a new
> > governance structure from CF checked in, I will update the driver.
> > As well, I think for this time being I will relax the lat,lon array
> > requirements. If needed by the community, it would be very easy to
> > compute, but I do not want the driver to be expensive in CPU and
> space.
> >
> > Thanks again,
> >
> > Regards,
> > Denis
> >
> > 2006/4/26, John Caron <caron at unidata.ucar.edu
> > <mailto:caron at unidata.ucar.edu>>:
> >
> > Hi Denis:
> >
> > 1) CF has unfortunately not yet dealt with datum and spheroid
> > encoding (not sure what "authority" is), but its on our list to
> > tackle. CF does specify a list of known projections and how to
> > encode those (Appendix F).
> >
> > 2) You can, of course, add any metadata you want, eg GeoTransform
> > values, from the CF POV, which CF readers are likely to ignore.
> >
> > 3) Frank Warmerdam and I talked a while ago about using WKT to
> > encode projection info. At the moment, it seems as good as any, with
> > the proviso that the CF group may decide to do it another way (when
> > we eventually decide).
> >
> > 4) Calculating the lat,lon arrays for projections is currently
> > required under CF. I have proposed that this requirement be relaxed,
> > perhaps as a CF profile, for the case where this is unneeded and
> > burdonsome. Issues like this are awaiting a new CF governence
> structure.
> >
> > 5) Unidata's software maps OPeNDAP datasets into the NetCDF data
> > model (aka "Common Data Model"), so we strongly encourage everyone
> > to use the NetCDF metadata conventions such as CF in their OPeNDAP
> > Servers. We think of OPeNDAP datasets as remote NetCDF datasets, and
> > make access to them as transparent as possible.
> >
> > 6) BTW, CF is an organization independent of Unidata. It grew out of
> > "climate and forecasting" modelers using NetCDF files, but is now
> > broader than that, and is an exemplar "community of practice" around
> > scientific metadata.
> >
> > I am cc'ing to the CF list in case anyone there wants to add more,
> > and so the list can hear about what you are trying to do. In case
> > anyone doenst know, GDAL is an excellent C library for geospatial
> > work, kind of a "Common Data Model" for C .
> >
> >
> > Denis Nadeau wrote:
> >> Hi,
> >>
> >> I have looked at the DODS OpeNDAP site and I could use the same
> > metadata
> >> structure to store NetCDF projection information. This way if
> > somebody
> >> needs to convert from GTIFF to NetCDF, all projecton information could
> >> be used by GRADS, Openev or other applications. I guess my main
> > problem
> >> is related on how the CF-1 convention from Unidata handle
> > projections.
> >> This bring me to a main question:
> >>
> >> What are the needs for projections in the GALEON projects?
> >>
> >> I am the current GDAL NetCDF driver programmer, and would like to make
> >> the driver as useful as it can be to the community.
> >>
> >> Thanks,
> >> Denis
> >>
> >>
> >> Here are some notes on what was planned for storing projection,
> > etc in
> >> other parts of GDAL drivers. To my knowledge, the never really
> >> propogated
> >> through to the OPeNDAP driver. If the NetCDF or HDF direct
> > access GDAL
> >> driver is updated that those changes propogate through to the
> > OPeNDAP
> >> driver so that the same NetCDF/HDF datasets are accessible via
> > native
> >> OPeNDAP server, Grads GDS and THREDDS.
> >>
> >> At this point, a lot more support is there for local NetCDF/HDF
> >> files than
> >> for support of those files through OPeNDAP. Its on my rather
> > large
> >> to do
> >> list, but somewhere in the 2 year timeframe.
> >>
> >> http://home.gdal.org/~warmerda/gdal_opendap_design.html
> > <http://home.gdal.org/%7Ewarmerda/gdal_opendap_design.html>
> (GeoTiff)
> >> http://gdal.maptools.org/frmt_dods.html
> >> <http://gdal.maptools.org/frmt_dods.html
> > <http://gdal.maptools.org/frmt_dods.html>> (DODS/OPeNDAP)
> >>
> >> Thanks!
> >> Rob
> >>
> >> On Wed, April 26, 2006 5:32 am, Denis Nadeau wrote:
> >> > Hi All,
> >> >
> >> > I would like to have suggestions from the community on the
> >> current needs
> >> > for the GDAL NetCDF driver. I am currently writing the
> > CreateCopy
> >> method to
> >> > allow people to convert from any GDAL supported format to
> > NetCDF CF-1
> >> > convention format.
> >> >
> >> > At this point I am stuck with projection issues. How should
> > I handle
> >> > DATUM,
> >> > SPHEROID and AUTHORITY? I can produce a lat lon arrays to
> >> reproject the
> >> > projected coordinates to lat/lon space but that may be expensive
> >> in cpu
> >> > and
> >> > space.
> >> >
> >> > I am thinking as well to create an array containning the
> >> GeoTransform
> >> > values
> >> > if found in the source file.
> >> >
> >> > adfGeoTransform[0] /* top left x */
> >> > adfGeoTransform[1] /* w-e pixel resolution */
> >> > adfGeoTransform[2] /* rotation, 0 if image is "north up" */
> >> > adfGeoTransform[3] /* top left y */
> >> > adfGeoTransform[4] /* rotation, 0 if image is "north up" */
> >> > adfGeoTransform[5] /* n-s pixel resolution */
> >> >
> >> >
> >> > Thanks for your suggestion,
> >> >
> >> > Best Regards,
> >> > Denis Nadeau
> >> >
> >>
> >>
> >> --
> >> Alaska Ocean Observing System
> >> Database Manager
> >> 907-474-7948
> >>
> >>
> >
> ===============================================================================
> >
> >>
> >> To unsubscribe galeon, visit:
> >> http://www.unidata.ucar.edu/mailing-list-delete-form.html
> >>
> >
> ===============================================================================
> >
> >>
> >>
> >>
> >
> >
> >
> >
> >
> > ------------------------------------------------------------------------
> >
> > _______________________________________________
> > CF-metadata mailing list
> > CF-metadata at cgd.ucar.edu
> > http://www.cgd.ucar.edu/mailman/listinfo/cf-metadata
>
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