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
>
>
