[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Fwd: Polar stereo projection parameter name problem



Hi John and Robb,

This is a follow up on an error in a variable name in a file served by the NCDC NOMADS TDS.  It turns out the source file is from ncep in grib.    Perhaps the GRIB iosp for these files is putting the wrong variable name in for the polar stereographic case.  The THREDDS catalog for such datasets is at:

  http://nomads.ncdc.noaa.gov:8085/thredds/catalogServices?catalog=http://nomads.ncdc.noaa.gov:8085/thredds/catalog/radar/StIV/2006/catalog.xml

The NCDC folks are talking about using ncML to correct the problem, but it could be that the grib iosp is putting the wrong name in.  I thought this was worth checking because, if it is the iosp, it will pop up on any TDS that serves grib files in polar stereographic.

-- Ben

---------- Forwarded message ----------
From: Steve.Ansari <address@hidden>
Date: Oct 18, 2007 7:09 AM
Subject: Re: Polar stereo projection parameter name problem
To: "Glenn.Rutledge" <address@hidden>
Cc: Ben Domenico < address@hidden>, John Caron <address@hidden>, Nomads NCDC <address@hidden>, Brian Nelson < address@hidden>, Rich Baldwin <address@hidden>

Hello all,

The STIV (Stage-4 Multisensor Precip from NCEP) are in GRIB files from NCEP. 

John,
Is this a parameter that should be different in the GRIB file?  Can we use NcML to describe an 'alias' for this parameter?  If so, can you send a sample. 

Thanks,
Steve



Glenn.Rutledge said the following on 10/18/2007 8:24 AM:
Hi Ben,
This server data is populated and maintained (mostly) by Steve Ansari and Brian Nelson.  They are cc;ed to this and I'm certain they'll look into it. 

It turns out that this data, and some others (GOES),k and projected grids have some " incompatibility" issues for their datum description while being access with the GeoPortal Tooklit by ESRI (aka our ACCESS conversions of late)- as reported by Rich Baldwin here and he's also cc:ed just in case this might be germane. 

Regards, Glenn

Ben Domenico wrote the following on 10/17/2007 3:36 PM:
 Hi Glenn,

You may not be the right person for this note, but I'll start with you with the idea you can forward it to the appropriate person.  As the note below from John Caron indicates, there is a problem with the name being used to specify the latitude coordinate for the polar stereographic coordinate system being used to serve STIV radar data on the nomads server.  The prescribed CF name is "straight_vertical_longitude_from_pole"  but the netCDF file uses "longitude_of_projection_origin."  According to John, this is not an uncommon error, but it would be good to fix it.

Thanks.

-- Ben

---------- Forwarded message ----------
From: John Caron <address@hidden >
Date: Oct 17, 2007 1:08 PM
Subject: Re: attached file
To: Ben Domenico <address@hidden>
_onclick_="return top.js.OpenExtLink(window,event,this)">address@hidden >, address@hidden

Hi Noman:

Unfortunately its common for these files to not follow the conventions exactly.

"longitude_of_projection_origin" should be "straight_vertical_longitude_from_pole". Its a common error, and we tend to try to be lenient in these cases, so our software would probably look for both names.

Ben, can we notify the writer? Also, can I get a sample of the file for my tests?

John

Ben Domenico wrote:
> Noman,
>
> I'm forwarding this message to John Caron who can help you with the
> details of the projection in that netCDF file.
>
> -- Ben
>
> On 10/16/07, * Nawajish Noman* <address@hidden
> <mailto: address@hidden>> wrote:
>
>     Hi Ben,
>
>     We are working on the problem with Polar stereographic projection. I
>     am comparing the grid_mapping parameters in the file (see your email
>     below) and the parameters listed on the CF Convention page at _
>     http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.0/cf-conventions.html#appendix-grid-mappings_
>     Example F.5.
>
>     *Example F.5. Polar stereographic*
>
>     grid_mapping_name = polar_stereographic
>
>
>
>     */Map parameters:/*
>
>     straight_vertical_longitude_from_pole
>
>     latitude_of_projection_origin - Either +90. or -90.
>
>     Either standard_parallel or scale_factor_at_projection_origin
>
>     false_easting
>
>     false_northing
>
>     *Parameters in file are:***
>
>     char Polar_Stereographic_projection_Grid;
>
>          :grid_mapping_name = "polar_stereographic";
>
>          :longitude_of_projection_origin = - 105.0; // double
>
>          :scale_factor_at_projection_origin = 0.933; // double
>
>     Here are my questions:
>
>     Q1: Some of the parameters are missing in file. What do we do about
>     missing parameters?
>
>     Q2: You have " longitude_of_projection_origin " in file but the CF
>     convention says " latitude_of_projection_origin" - What do with
>     "longitude_of_projection_origin "?
>
>     We look for parameters listed in CF Conventions and map them to our
>     Spatial reference parameters. If parameters are missing in file we
>     assume default value. If incorrect parameters are specified - we
>     ignore them.
>
>     I want to make sure we are reading the parameters from your file
>     correctly. Please comment…
>
>     Thanks,
>
>     Noman
>
>     -----Original Message-----
>     From: address@hidden <mailto:address@hidden> [
>     mailto: address@hidden] On Behalf Of Ben Domenico
>     Sent: Tuesday, June 05, 2007 1:56 PM
>     To: Steve Kopp
>     Cc: Nawajish Noman
>     Subject: Re: attached file
>
>     Steve,
>
>     I'll attach jpegs of the dataset as displayed in arcMap and one from
>
>     the IDV.  In each case, you can see at the bottom of the screen, the
>
>     lat/lon values associated with the cursor position.  I'll also append
>
>     the ncDump output which shows the projection information -- in netCDF
>
>     terms (i.e., Polar_Stereographic_projection_Grid) anyway.
>
>     -- Ben
>
>     ncDump output
>
>     ===================================================
>
>     netcdf C:/Documents and
>     Settings/ben/Desktop/ST4.2006010100.06hWithLatLon.nc {
>
>      dimensions:
>
>        time = 1;   // (has coord.var)
>
>        y = 815;   // (has coord.var)
>
>        x = 1121;   // (has coord.var)
>
>      variables:
>
>        float Total_precipitation(time=1, y=815, x=1121);
>
>          :units = "kg/m^2";
>
>          :long_name = "Total precipitation @ surface";
>
>          :missing_value = -9999.0f; // float
>
>          :grid_mapping = "Polar_Stereographic_projection_Grid";
>
>          :GRIB_param_name = "Total precipitation";
>
>          :GRIB_center_id = 7; // int
>
>          :GRIB_table_id = 2; // int
>
>          :GRIB_param_number = 61; // int
>
>          :GRIB_param_id = 1, 7, 2, 61; // int
>
>          :GRIB_product_definition_type = "Accumulation";
>
>          :GRIB_level_type = 1; // int
>
>        int time(time=1);
>
>          :long_name = "forecast time";
>
>          :units = "hour since 2005-12-31T12:00:00Z";
>
>          :GRIB_orgReferenceTime = "2005-12-31T12:00:00Z";
>
>          :GRIB2_significanceOfRTName = "Start of forecast";
>
>          :_CoordinateAxisType = "Time";
>
>        double y(y=815);
>
>          :units = "km";
>
>          :long_name = "y coordinate of projection";
>
>          :standard_name = "projection_y_coordinate";
>
>          :grid_spacing = "4.763 km";
>
>          :_CoordinateAxisType = "GeoY";
>
>        double x(x=1121);
>
>          :units = "km";
>
>          :long_name = "x coordinate of projection";
>
>          :standard_name = "projection_x_coordinate";
>
>          :grid_spacing = "4.763 km";
>
>          :_CoordinateAxisType = "GeoX";
>
>        char Polar_Stereographic_projection_Grid;
>
>          :grid_mapping_name = "polar_stereographic";
>
>          :longitude_of_projection_origin = -105.0; // double
>
>          :scale_factor_at_projection_origin = 0.933 ; // double
>
>          :earth_shape = "spherical";
>
>          :GRIB_param_Dx = 4763.0; // double
>
>          :GRIB_param_Dy = 4763.0; // double
>
>          :GRIB_param_GDSkey = 1294122487; // int
>
>          :GRIB_param_La1 = 23.117; // double
>
>          :GRIB_param_Lo1 = -119.023; // double
>
>          :GRIB_param_LoV = -105.0; // double
>
>          :GRIB_param_Nx = 1121; // int
>
>          :GRIB_param_Ny = 881; // int
>
>          :GRIB_param_ProjFlag = 0; // int
>
>          :GRIB_param_ResCompFlag = 8; // int
>
>          :GRIB_param_ScanningMode = 64; // int
>
>          :GRIB_param_grid_name = "Polar Stereographic projection Grid";
>
>          :GRIB_param_grid_radius_spherical_earth = 6367.47; // double
>
>          :GRIB_param_grid_shape = "spherical";
>
>          :GRIB_param_grid_shape_code = 0; // int
>
>          :GRIB_param_grid_type = 5; // int
>
>          :_CoordinateTransformType = "Projection";
>
>          :_CoordinateAxisTypes = "GeoX GeoY";
>
>        double lat(y=815, x=1121);
>
>          :units = "degrees_north";
>
>          :long_name = "latitude coordinate";
>
>          :standard_name = "latitude";
>
>          :_CoordinateAxisType = "Lat";
>
>        double lon(y=815, x=1121);
>
>          :units = "degrees_east";
>
>          :long_name = "longitude coordinate";
>
>          :standard_name = "longitude";
>
>          :_CoordinateAxisType = "Lon";
>
>      :History = "GridDatatype extracted from dataset
>
>     /eclipse1a/ftp/pub/radar/StIV/2006/01/01/hr/ST4.2006010100.06h";
>
>      :Conventions = "CF-1.0";
>
>      :Originating_center = "US National Weather Service (NCEP) subcenter
>     = 4";
>
>      :Generating_Process_or_Model = "River Forecast Center Quantitative
>
>     Precipitation estimate mosaic generated by NCEP";
>
>      :Product_Type = "Accumulation";
>
>      :cdm_data_type = "Grid";
>
>      :creator_name = "US National Weather Service (NCEP) subcenter = 4";
>
>      :file_format = "GRIB-1";
>
>      :location =
>     "/eclipse1a/ftp/pub/radar/StIV/2006/01/01/hr/ST4.2006010100.06h";
>
>      :history = "Direct read of GRIB into NetCDF-Java 2.2 API";
>
>      :_CoordinateModelRunDate = "2005-12-31T12:00:00Z";
>
>     =====================================================
>
>     On 6/5/07, Steve Kopp < address@hidden <mailto:address@hidden>> wrote:
>
>     >
>
>     >  Ben, the dataset contains no projection information. Without this, we
>
>     >  won't know where else to draw anything.
>
>     >
>
>     >  Could you send us a screen shot of what you are seeing?
>
>     >
>
>     >  Thanks,
>
>     >
>
>     >  Steve
>
>     >
>
>     >
>
>     >  -----Original Message-----
>
>     >  From: address@hidden <mailto:address@hidden> [
>     mailto:address@hidden] On Behalf Of
>
>     >  Ben Domenico
>
>     >  Sent: Tuesday, June 05, 2007 11:32 AM
>
>     >  To: Steve Kopp
>
>     >  Subject: attached file
>
>     >
>
>     >  Hi Steve,
>
>     >
>
>     >  Don't know if this will work, but I'm attaching one of the CF-netCDF
>
>     >  files I got from that NCDC radar data server.  Let me know whether
>
>     >  this comes through OK.
>
>     >
>
>     >  -- Ben
>
>     >
>
>     >
>
>


-- 
Glenn K. Rutledge
Services Team Leader
Remote Sensing and Applications Division
NOMADS Project Manager
National Oceanic and Atmospheric Administration
National Climatic Data Center
Asheville NC 28801
Phone: (828) 271-4097
Fax: (828) 271-4328

NOMADS: http://nomads.ncdc.noaa.gov/

-- 
Steve Ansari
Physical Scientist
NOAA's National Climatic Data Center
Veach-Baley Federal Building
151 Patton Avenue
Asheville, NC 28801
Ph: 828-271-4611
Fax: 828-271-4022