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NOTICE: This version of the NSF Unidata web site (archive.unidata.ucar.edu) is no longer being updated.
Current content can be found at unidata.ucar.edu.
To learn about what's going on, see About the Archive Site.
Hi Jon, Whoops! Sorry about that. A few possibilities: 1) It would be pretty easy to change the TDS to give you back a NetcdfDataset instead of a GridDataset. You could use that for the enhancement information and convert it to a GridDataset to get all the grid goodness out of it. 2) We could (probably should) expose the enhancement information in GridDataset. 3) Yuck! Dipping into implementation details. -- The only implementation of ucar.nc2.dt.GridDataset is by ucar.nc2.dt.grid.GridDataset which has a public getNetcdfDataset() method. Number 2 would be my first choice. Though I'm trying to think of any other reasons it would be useful for the WMS code to have a NetcdfDataset instead of GridDataset. Ethan On 2/11/2010 1:46 PM, Jonathan Blower wrote: > Hi Ethan, > > Thanks but there's no public getEnhanceMode() method on VariableDS > (http://www.unidata.ucar.edu/software/netcdf-java/v4.1/javadoc/ucar/nc2/ > dataset/VariableDS.html). There's a similar method on NetcdfDataset > though: > http://www.unidata.ucar.edu/software/netcdf-java/v4.1/javadoc/ucar/nc2/d > ataset/class-use/NetcdfDataset.Enhance.html. > > But I can't get a handle to the NetcdfDataset if all I have is a > GridDataset (I think). > > Along similar lines, is there a way to get the underlying file type of a > GridDataset/GridDatatype (so I can optimise data-reading algorithms > based on what sort of file I'm reading from)? > NetcdfDataset.getFileTypeId() works for a NetcdfDataset, but again I > can't get this if all I have is a GridDataset. > > In case you hadn't guessed, this is all part of my effort to refactor > ncWMS to be more integrable with TDS. From our previous conversations I > believe that TDS will give me GridDataset objects, so that's why I'm > trying to work at this level, but if there's a way that the TDS config > system could pass me higher-level objects that could work too. Any > thoughts? > > Cheers, Jon > > > > -----Original Message----- > From: Ethan Davis [mailto:edavis@xxxxxxxxxxxxxxxx] > Sent: 11 February 2010 18:34 > To: Jonathan Blower > Cc: netcdf-java@xxxxxxxxxxxxxxxx > Subject: Re: Can I tell if a GridDatatype is "enhanced"? > > Hi Jon, > > Not very straight forward and there may be some loopholes I'm missing > that John can comment on when he returns. > > If you call getVariable() on your GridDataype, you will get the backing > VariableDS. Call getEnhanceMode() on that and you'll get an > EnumSet<NetcdfDataset.Enhance>. If that Set contains > Enhance.ScaleMissing, the data you get back will have already had the > scale/offset/missing applied. If that set contains > Enhance.ScaleMissingDefer, you can directly use > VariableDS.convertScaleOffsetMissing() to convert the data. > > VariableDs also implements VariableEnhance.enhance(Set<Enhance>) but the > comments say "DO NOT USE DIRECTLY. public by accident". I'll leave it to > John to explain that and comment on the possibility of exposing any of > this directly through the GridDatatype. > > Ethan > > On 2/8/2010 8:05 AM, Jonathan Blower wrote: >> Hi, >> >> I'm writing a method along the lines of: >> >> double[] extractDataFrom(GridDatatype grid); >> >> where the GridDatatype is being passed to me by "foreign" code out of > my >> control. Do I have any way of telling whether the GridDatatype is >> "enhanced", i.e. whether scale/offset/missing attributes are >> automatically applied when I extract data? >> >> And does it matter? Can I program defensively to take care of both >> situations (enhanced and not enhanced)? I'm worried that simply >> applying convertScaleOffsetMissing() to a value from an enhanced >> GridDatatype might actually apply the enhancements twice and hence > give >> me the wrong answer. >> >> Thanks, >> Jon
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