|
Hi Jian, We have been working over the last couple of Ferret releases on how Ferret defines grids. Previously we did not insist that a dimension had the same direction in all grids. This lead to inconsistencies, where a dimension would be the T axis in one grid and the X axis in another grid. In older versions we also did a lot with the names of coordinate axes, and that led to odd stuff too, such as TSTATION being assigned to the T direction where it really should have been an X axis. So we implemented changes where dimensions should have the same direction in all grids, and we don't use dimension names but rely on coordinate variable attributes to determine their directions. The axis attribute, or standard names that define a direction, or units that are unique to a direction let us assign the right direction. This means that files such as yours which have the dimensions declared, but do not have coordinate variables for some of the dimensions, sometimes give Ferret problems in defining the grids. Your NetCDF header is, netcdf svdpactp { dimensions: lat = 20 ; latitude = 20 ; longitude = 68 ; z = 10 ; time = 22 ; variables: double latitude(latitude) ; latitude:units = "degree_north" ; double lat(latitude) ; lat:units = "degree_north" ; double longitude(longitude) ; longitude:units = "degree_east" ; double lam(z) ; double lamt(z) ; double lamp(z) ; double txy(z, latitude, longitude) ; double pxy(z, lat, longitude) ; double tti(time, z) ; double pti(time, z) ; } Latitude, lat, and longitude are coordinate variables and their direction is determined by their units, but z and time are simply dimensions, so there aren't any attributes to use in setting their direction. In our next release we are backing off of the decision to not use dimension names. If the dimension name is a single letter x, y, z, t; or if it is time, date, layer, level, or starts with lon, lat, dep, elev, hei, or alt, we'll go ahead and put it in the appropriate direction. Here is how your file looks when I open it in the beta version of Ferret v6.85 (not yet released): NOAA/PMEL TMAP A further idea which we have not yet implemented is to allow the user to specify what dimension gets what direction, when opening the file. On 5/30/2013 11:57 AM, Jian Ma wrote:
|