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Re: Accessing a GDS dataset with the LAS

Dave Brown wrote:
> The original dataset encodes the time dimension as days since the
> beginning of the year, in this case 1990. This means the 1 hour
> timestep is fractional --  0.0416666666 days. GDS adjusts the
> time unit to "days since 1-1-1 00:00:0.0", so the starting time,
> as presented by DODS, is 726469.0.

Hi, Dave -- 

My understanding is that the metadata accompanying a GDS
dataset is generated by GrADS, so it may be relevant how you
describe the original dataset to GrADS in order to serve it
with your GDS. It sounds like somewhere in there the time
zero got changed from 1-1-1990 to 1-1-1. Can you point me to
the DODS URL where this GDS data set is located? Would it be
possible for me to access the original data directly with
GrADS using my account on motherlode at NCAR? 

> The LAS xml for the time dimension, as generated by the addXml.pl
> script using the first file in the dataset as input,
> reads as follows:
> <h0001_nc_time units="hour" type="t">
>   <arange start="1990-01-01 00:00:00" step="1" size="8760"/>
> </h0001_nc_time>

It's been a while since I've thought about LAS xml coding,
but here the units are hours, so that may be one source of
error. Are you describing the original data set (in 365
separate files) or the GDS data set (1 DODS URL) to the LAS? 

> LAS 5.0 read the xml and generated the user interface for this
> dataset without problems (*), but when I try to access the data I get
> this error from Ferret:
>  *** NOTE: Coordinates out of order or missing on axis time at
> subscript 2163
>  *** NOTE: A dummy axis of subscripts will be used
> ...
>  **ERROR: illegal limits: "FOSSIL" is not in the range T=-8.082E+16
>           Axis extremes are T=0.5:8761

Does it change anything if you skip over the LAS and just
try to read the DODS URL with Ferret? 

Perhaps the LAS and Ferret experts from PMEL will have
additional insights... 


Jennifer Miletta Adams
Center for Ocean-Land-Atmosphere Studies
4041 Powder Mill Road, Suite 302
Calverton, MD 20705-3106
Phone: (301)902-1278 or (301)595-7000
Fax:   (301)595-9793
Email: jma@cola.iges.org

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