Hi Steve,
Yes, we've seen this problem before and have it on our list
(https://www.unidata.ucar.edu/jira/browse/TDS-250) but somehow it hasn't
floated to the top yet. We currently have it scheduled for TDS 4.4
(we're working on 4.3 currently).
Ethan
On 7/11/2012 12:54 PM, Steve Ansari wrote:
> Hello John (and all),
>
> We've run into a problem using the 'As Point Dataset' time series
> request with Polar Stereographic data on the TDS (version 4.2.10). For
> some requests we are getting the message:
>
> Requested Lat/Lon Point (+80.33N 138.6W) is not contained in the Data
> Data Bounding Box = lat= [30.92,90.00] lon= [-80.73,168.34]
>
> as seen in this request:
> http://data.ncdc.noaa.gov/thredds/ncss/grid/cdr/seaice/seaice_north.ncml?var=seaice_conc_cdr&latitude=80.33203&longitude=-138.69141&temporal=range&time_start=2007-01-31T00:00:00Z&time_end=2007-12-31T00:00:00Z&vertCoord=0&accept=xml&point=true
>
>
> The underlying issue seems to be in how the GridDataset CDM class
> calculates the bounding box for this Polar Stereographic dataset. The
> bounding box should be something like lat=[31, 90], lon=[-180, 180].
> Has anyone else run into problems with the Bounding Box calculations
> for projected datasets? Perhaps the NetCDF-Java API is only sampling
> the corners (and perhaps some points in between) of the coordinate axes
> to determine the bounding box. I would think this works for the other
> NetCDF-Java supported projections, but might cause issues with the
> Stereographic projections.
>
> I'm pasting some sample code below to show that brute force reading of
> each coordinate axis element value produces the correct bounding box:
>
> Thanks for your help!
>
> Steve
>
>
>
> package steve.test;
>
> import ucar.ma2.Array;
> import ucar.nc2.dt.GridDatatype;
> import ucar.nc2.dt.grid.GridDataset;
> import ucar.unidata.geoloc.LatLonPoint;
> import ucar.unidata.geoloc.LatLonPointImpl;
> import ucar.unidata.geoloc.Projection;
> import ucar.unidata.geoloc.ProjectionPoint;
> import ucar.unidata.geoloc.ProjectionPointImpl;
>
> public class TestGridAsPointSubsetService {
>
> public static void main(String[] args) {
> try {
> String dodsURL =
> "http://data.ncdc.noaa.gov/thredds/dodsC/cdr/seaice/seaice_north.ncml";;
> GridDataset gds = GridDataset.open(dodsURL);
> System.out.println(gds.getBoundingBox());
>
> GridDatatype grid = gds.findGridDatatype("seaice_conc_cdr");
> System.out.println(grid.getCoordinateSystem().getLatLonBoundingBox());
> double minX = grid.getCoordinateSystem().getXHorizAxis().getMinValue();
> double maxX = grid.getCoordinateSystem().getXHorizAxis().getMaxValue();
> double minY = grid.getCoordinateSystem().getYHorizAxis().getMinValue();
> double maxY = grid.getCoordinateSystem().getYHorizAxis().getMaxValue();
> System.out.println("min x: "+minX);
> System.out.println("max x: "+maxX);
> System.out.println("min y: "+minY);
> System.out.println("max y: "+maxY);
> Projection proj = grid.getProjection();
> ProjectionPoint projPointLL = new ProjectionPointImpl(minX, minY);
> LatLonPoint llPointLL = proj.projToLatLon(projPointLL, new
> LatLonPointImpl());
> ProjectionPoint projPointUR = new ProjectionPointImpl(maxX, maxY);
> LatLonPoint llPointUR = proj.projToLatLon(projPointUR, new
> LatLonPointImpl());
> System.out.println(llPointLL + " , "+llPointUR);
> Array xAxisData = grid.getCoordinateSystem().getXHorizAxis().read();
> Array yAxisData = grid.getCoordinateSystem().getYHorizAxis().read();
> double minLat = Double.POSITIVE_INFINITY;
> double maxLat = Double.NEGATIVE_INFINITY;
> double minLon = Double.POSITIVE_INFINITY;
> double maxLon = Double.NEGATIVE_INFINITY;
> LatLonPointImpl llp = new LatLonPointImpl();
> ProjectionPointImpl ppt = new ProjectionPointImpl();
> float[] xData = (float[])xAxisData.copyTo1DJavaArray();
> float[] yData = (float[])yAxisData.copyTo1DJavaArray();
>
> for (float y : yData) {
> for (float x : xData) {
> ppt.setLocation(x, y);
> llp = (LatLonPointImpl) proj.projToLatLon(ppt, llp);
> minLat = (llp.getLatitude() < minLat) ? llp.getLatitude() : minLat;
> maxLat = (llp.getLatitude() > maxLat) ? llp.getLatitude() : maxLat;
> minLon = (llp.getLongitude() < minLon) ? llp.getLongitude() : minLon;
> maxLon = (llp.getLongitude() > maxLon) ? llp.getLongitude() : maxLon;
> }
> }
> // brute force range
> System.out.println("brute force lat range: "+minLat+" , "+maxLat + " |
> lon range: " + minLon + " , " + maxLon);
> // subset service TDS URL:
> //
> http://data.ncdc.noaa.gov/thredds/ncss/grid/cdr/seaice/seaice_north.ncml?var=seaice_conc_cdr&latitude=80.33203&longitude=-138.69141&temporal=range&time_start=2007-01-31T00:00:00Z&time_end=2007-12-31T00:00:00Z&vertCoord=0&accept=xml&point=true
> } catch (Exception e) {
> e.printStackTrace();
> }
> }
> }
>
>
>
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--
Ethan Davis UCAR Unidata Program
edavis@xxxxxxxxxxxxxxxx http://www.unidata.ucar.edu
