Re: Help with ncML for aggregation

• To: mrehbein@xxxxxxxxxxx
• Subject: Re: Help with ncML for aggregation
• From: John Caron <caron@xxxxxxxxxxxxxxxx>
• Date: Fri, 01 Aug 2003 16:47:48 -0600

mrehbein@xxxxxxxxxxx wrote:

Hi John,

I have had a bit of a break from the netcdf project I had been working on, but now I am back on the trail :)

My geoTiff writer needs a bit of work, but it uses JAI to create a tiff:

JAI.create("filestore", bufferedImage, filepath, "TIFF", null);

and then a write a text "world file" to match the tiff image.

The only problem I came across was that the numbers in the world file needed to be in the following format:

DecimalFormat format=new DecimalFormat(".00000000000000");

The numbers in the world file (in order) needed to be:

xscale
brotation
crotation
yscale
xOriginCentre
yOriginCentre

In any case, when I tidy up the code into a neat little API, I will forward it on to you.

great, id like to see it.

---

I have a question or two about NcML.

I am using NcML to aggregate netcdf files that hold data for a particular month. Below is a copy of my test NcML file.

<netcdf xmlns="http://www.ucar.edu/schemas/netcdf"; xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"; xsi:schemaLocation="http://www.unidata.ucar.edu/schemas/netcdf.xsd http://www.unidata.ucar.edu/schemas/netcdfDataset.xsd";>

<dimension name="lat" length="2100" /> <dimension name="lon" length="1600" /> <dimension name="time" length="61"/>

 <variable name="SST_AVE" type="float" shape="time lat lon"/>

 <netcdf uri="file://\\moon\risdev\ferret\data\mar.nc">
   <dimension name="time" length="31" />
 </netcdf>

 <netcdf uri="file://\\moon\risdev\ferret\data\apr.nc">
   <dimension name="time" length="30" />
 </netcdf>

</netcdf>

I could get the java NetCDF API to read it and aggregate, using the following code segment:

<code>

NetcdfFile ncfile = NetcdfDataset.factory("C:\\sst_ncml.xml",null);

NetcdfDataset nDataset = ucar.nc2.dataset.conv.Convention.factory(ncfile); // find the coordinate system used in this netcdf file

List systems=nDataset.getCoordinateSystems();
Iterator iSys=systems.iterator();
while (iSys.hasNext()) {
 CoordinateSystem sys=(CoordinateSystem)iSys.next();
 GridCoordSys grid=new GridCoordSys(sys);

Date fromDate=aims.util.StringUtilities.convert2Date("11/03/2003");

 Date thruDate=aims.util.StringUtilities.convert2Date("26/04/2003");

int minT=grid.findTimeCoordElement(fromDate);

 int maxT=grid.findTimeCoordElement(thruDate);

System.out.println("date indexs:" + minT + " " + maxT);

}

</code>

However, there are zero coordinates systems, so the code within the while loop never executes. I assume I must define a coordinate system within the NcML file, which I have done and the XML is shown in the attachment. The code within the while loop still does not execute. Can you tell me what am I doing wrong?

Thanks for your time,

Mark

the dataset aggregation is very "alpha" quality, so it may be a bug.

thanks,

John