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CDM Validator


Common Data Model Coordinate System Validation Help

last updated Feb 07, 2006

Dataset= ecmwf_era-40_subset.nc

This is the name of the uploaded file.

Summary

No CoordSysBuilder found - using default (GDV). No 'Conventions' global attribute.

If there are problems that the Validator was able to recognize, a summary of them is here. The absence of any diagnostic message here may mean that your file is ok, or it may mean that the Validator simply didnt recognize the problem(s).

In this example, the global attribute "Convention" was not found, and no other CoordSysBuilder was found that understood this file, so the Validator is using the default. Each different Convention, such as CF-1.0, COARDS, etc. has its own CoordSysBuilder class in the NetCDF-Java library.

Convention=CF-1.0

This is the name of the CoordSysBuilder used by the Validator.

Coordinate Axes

Name Declaration AxisType units udunits regular
latitude float latitude(latitude=73) Lat degrees_north 0.0174533 rad 1.003
longitude float longitude(longitude=144) Lon degrees_east 0.0174533 rad 2.005
time int time(time=62) Time hours since 1900-01-01 00:00:0.0 date 12

These are the Coordinate Axes found in this file. Coordinate Systems are built from these.

Grid Coordinate Systems

Name X Y Vertical Time
time-latitude-longitude longitude latitude time

These are the Coordinate Systems found in the file. This version of the Validator is only looking for gridded, georeferencing Coordinate Systems, which have an X, Y, and optional Z and T coordinate axes.

Grid variables

Name Declaration units udunits CoordSys
blh double blh(time=62, latitude=73, longitude=144) m m time-latitude-longitude
lcc double lcc(time=62, latitude=73, longitude=144) (0 - 1) false time-latitude-longitude
p10u double p10u(time=62, latitude=73, longitude=144) m s**-1 false time-latitude-longitude
p2d double p2d(time=62, latitude=73, longitude=144) K K time-latitude-longitude

This is the list of data variables that have georeferencing Coordinate Systems, and are viewable through the IDV. If this list is empty, then either this dataset does not have any grids in it, or the Validator was unable to recognize them, possibly because the file does not properly implement the Convention.

In this example, note that "(0 - 1)" and "m s**-1" are not valid udunits. It is recommended that data variables use udunits, but its not necessarily fatal if they don't. "(0 - 1)" probably indicates a dimensionless flag whose value is 0 or 1. The "correct" udunit would be an empty string. The "m s**-1" unit should be changed to"m s-1" or "m/s"

Non-Grid variables

Name Declaration units udunits CoordSys

Any variables that are not Coordinate Axes or Grid variables are listed here.


Example Problem Datasets

Summary:

Convention=CF-1.0

Coordinate Axes

Name Declaration AxisType units udunits
lat float lat(lat=182) degrees north 0.017453292519943295 rad
lon float lon(lon=362) degrees east 0.017453292519943295 rad
time float time(time=12) Time days since 0000-01-01 00:00:00 date

Grid Coordinate Systems

Name X Y Vertical Time

Grid variables

Name Declaration units udunits CoordSys

Non-Grid variables

Name Declaration units udunits CoordSys
date int date(time=12) yyyymmdd time
datesec int datesec(time=12) seconds time
ifrac float ifrac(time=12, lat=182, lon=362) lat-lon-time
sst float sst(time=12, lat=182, lon=362) degrees C 0.017453292519943295 A.rad.s lat-lon-time

This is supposed to be CF-1.0, but no grid variables are being found. The problem is a bit subtle, but is indicated by the fact that the lat and lon Coordinate Axes do not have an assigned AxisType. The units look good, dont, they? On closer inspection, one sees that "degrees north" should be "degrees_north", and "degrees east" should be "degrees east", according to CF-1.0 sections 4.1 and 4.2. Fixing that will make this dataset correctly conform to the CF-1.0 specification.

The other problem here is that "degrees C" is being misinterpeted as a unit of Radian - Coulombs (Ampere-second)! The correct udunit for this is Celsius.


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