Changes between Initial Version and Version 1 of ArcNetCDF_examples


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Timestamp:
09/13/07 20:45:41 (14 years ago)
Author:
rsignell
Comment:

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  • ArcNetCDF_examples

    v1 v1  
     1Examples of ArcGIS 9.2 NetCDF output for a 2D topographic grid using the  "RasterToNetCDF" command.   Here three different coordinate systems were used: Geographic, UTM, and Miller. ArcGIS encodes the Coordinate System Specification in a variable attribute called "esri_pe_string" that contains a complete specification in ESRI WKT (similar but not the same as OGC WKT).
     2
     3For Geographic, we get something that is CF compliant:
     4
     5{{{
     6[rsignell@ricsigdtlx cf]$ ncdump -h test36_arc.nc
     7netcdf test36_arc {
     8dimensions:
     9        lon = 151 ;
     10        lat = 80 ;
     11variables:
     12        double lon(lon) ;
     13                lon:long_name = "longitude coordinate" ;
     14                lon:standard_name = "longitude" ;
     15                lon:units = "degrees_east" ;
     16        double lat(lat) ;
     17                lat:long_name = "latitude coordinate" ;
     18                lat:standard_name = "latitude" ;
     19                lat:units = "degrees_north" ;
     20        float topo(lat, lon) ;
     21                topo:long_name = "topo" ;
     22                topo:esri_pe_string = "GEOGCS[\"GCS_WGS_1984\",DATUM[\"D_WGS_1984\",SPHEROID[\"WGS_1984\",6378137.0,298.257223563]],PRIMEM[\"Greenwich\",0.0],UNIT[\"Degree\",0.0174532925199433]]" ;
     23                topo:coordinates = "lon lat" ;
     24                topo:units = "Degree" ;
     25                topo:missing_value = 0.f ;
     26
     27// global attributes:
     28                :Conventions = "CF-1.0" ;
     29                :Source_Software = "ESRI ArcGIS" ;
     30}
     31
     32}}}
     33
     34For non-geographic projections, if known to CF, it adds the "grid_mapping" variable.  So for UTM, we get:
     35
     36{{{
     37
     38[rsignell@ricsigdtlx cf]$ ncdump -h test36_utm_arc.nc
     39netcdf test36_utm_arc {
     40dimensions:
     41        x = 141 ;
     42        y = 101 ;
     43variables:
     44        double x(x) ;
     45                x:long_name = "x coordinate of projection" ;
     46                x:standard_name = "projection_x_coordinate" ;
     47                x:units = "Meter" ;
     48        double y(y) ;
     49                y:long_name = "y coordinate of projection" ;
     50                y:standard_name = "projection_y_coordinate" ;
     51                y:units = "Meter" ;
     52        float topo(y, x) ;
     53                topo:long_name = "topo" ;
     54                topo:esri_pe_string = "PROJCS[\"NAD_1983_UTM_Zone_19N\",GEOGCS[\"GCS_North_American_1983\",DATUM[\"D_North_American_1983\",SPHEROID[\"GRS_1980\",6378137.0,298.257222101]],PRIMEM[\"Greenwich\",0.0],UNIT[\"Degree\",0.0174532925199433]],PROJECTION[\"Transverse_Mercator\"],PARAMETER[\"False_Easting\",500000.0],PARAMETER[\"False_Northing\",0.0],PARAMETER[\"Central_Meridian\",-69.0],PARAMETER[\"Scale_Factor\",0.9996],PARAMETER[\"Latitude_Of_Origin\",0.0],UNIT[\"Meter\",1.0]]" ;
     55                topo:coordinates = "x y" ;
     56                topo:grid_mapping = "transverse_mercator" ;
     57                topo:units = "Meter" ;
     58                topo:missing_value = 0.f ;
     59        int transverse_mercator ;
     60                transverse_mercator:grid_mapping_name = "transverse_mercator" ;
     61                transverse_mercator:longitude_of_central_meridian = -69. ;
     62                transverse_mercator:latitude_of_projection_origin = 0. ;
     63                transverse_mercator:scale_factor_at_central_meridian = 0.9996 ;
     64                transverse_mercator:false_easting = 500000. ;
     65                transverse_mercator:false_northing = 0. ;
     66
     67// global attributes:
     68                :Conventions = "CF-1.0" ;
     69                :Source_Software = "ESRI ArcGIS" ;
     70}
     71}}}
     72
     73For a projection that isn't Geographic, and isn't defined one of the accepted "grid_mapping" projections in CF, just the esri_pe_string is written, as in this Miller Projection:
     74
     75{{{
     76[rsignell@ricsigdtlx cf]$ ncdump -h test36_miller_arc.nc
     77netcdf test36_miller_arc {
     78dimensions:
     79        x = 144 ;
     80        y = 92 ;
     81variables:
     82        double x(x) ;
     83                x:long_name = "x coordinate of projection" ;
     84                x:standard_name = "projection_x_coordinate" ;
     85                x:units = "Meter" ;
     86        double y(y) ;
     87                y:long_name = "y coordinate of projection" ;
     88                y:standard_name = "projection_y_coordinate" ;
     89                y:units = "Meter" ;
     90        float topo(y, x) ;
     91                topo:long_name = "topo" ;
     92                topo:esri_pe_string = "PROJCS[\"Miller Cylindrical\",GEOGCS[\"GCS_North_American_1983\",DATUM[\"D_North_American_1983\",SPHEROID[\"GRS_1980\",6378137.0,298.257222101]],PRIMEM[\"Greenwich\",0.0],UNIT[\"Degree\",0.0174532925199433]],PROJECTION[\"Miller_Cylindrical\"],PARAMETER[\"False_Easting\",0.0],PARAMETER[\"False_Northing\",0.0],PARAMETER[\"Central_Meridian\",-70.0],UNIT[\"Meter\",1.0]]" ;
     93                topo:coordinates = "x y" ;
     94                topo:units = "Meter" ;
     95                topo:missing_value = 0.f ;
     96
     97// global attributes:
     98                :Conventions = "CF-1.0" ;
     99                :Source_Software = "ESRI ArcGIS" ;
     100}
     101}}}
     102