Re: [netcdf-java] Problem with findXYindexFromLatLon() on a Geogrid subset

• To: franck.reinquin@xxxxxxx
• Subject: Re: [netcdf-java] Problem with findXYindexFromLatLon() on a Geogrid subset
• From: John Caron <caron@xxxxxxxx>
• Date: Wed, 11 Mar 2015 12:57:12 -0600

Hi Franck:

I have a fix for this checked into both 4.5.6 and 6.0. I can build a
snapshot release for you if you want.

John

On Wed, Mar 11, 2015 at 10:40 AM, John Caron <caron@xxxxxxxx> wrote:

> Hi Franck:
>
> yes, its a bug in GeoGrid.makeSubset(). Im working on a fix.
>
> thanks for the nice unit test, made it easy to find.
>
> John
>
> On Wed, Mar 11, 2015 at 6:15 AM, <franck.reinquin@xxxxxxx> wrote:
>
>> Hello,
>>
>> I have problems with the findXYindexFromLatLon() method used with a
>> Geogrid subset.
>> gcs.getLatLon(0,0) gives me lat/long coordinates that I try to convert
>> back to XY coordinates.
>> But I get -1 for the X coordinate.
>> On the original grid, everything is fine.
>>
>> The attached example reads one of the sample netCDF files from the
>> Unidata website. I'm using netcdfAll-4.5.jar dated March, 6 (v 4.5.5).
>>
>> Does anyone see what I did wrong ? Code and output below. The "start"
>> members look strange.
>>
>> Thanks,
>> Franck
>>
>> ------------------------------
>> *Output :*
>>
>> Grid name =area
>> WHOLE GRID
>> is lat/lon system ? true
>> gcs bounding box : latmin=-88.927734375 latmax=88.927734375 lonmin=0.0
>> lonmax=358.59375
>> projection       : LatLonProjection
>> width =256, height=128
>> X is regular     ? true
>> X is contiguous  ? true
>> X start          : 0.0
>> X increment      : 1.40625
>> Y is regular     ? false
>> Y is contiguous  ? true
>> Y start          : -88.927734375
>> Y increment      : 1.4004367618110236
>> index (0,0) --> lat/lon : -88.927734375 ; 0.0
>> index (1,1) --> lat/lon : -87.53870391845703 ; 1.40625
>> looking up lat=-87.53870391845703  lon=1.40625
>> index= (1, 1)
>>
>> SUBGRID (latmin=-20.0  latmax=-10.0  lonmin=35.0  lonmax=45.0)
>> is lat/lon system ? true
>> gcs bounding box : latmin=-20.31112289428711 latmax=-10.505756378173828
>> lonmin=35.15625 lonmax=45.0
>> projection       : LatLonProjection
>> width =8, height=8
>> X is regular     ? true
>> X is contiguous  ? true
>> X start          : 0.0
>> X increment      : 1.40625
>> Y is regular     ? false
>> Y is contiguous  ? true
>> Y start          : 0.0
>> Y increment      : 1.4004367618110236
>> index (0,0) --> lat/lon : -20.31112289428711 ; 35.15625
>> index (1,1) --> lat/lon : -18.910356521606445 ; 36.5625
>> looking up lat=-18.910356521606445  lon=36.5625
>> index= (-1, 1)
>>
>> -------------------------
>> try {
>> GridDataset dataset = GridDataset.open("
>> http://www.unidata.ucar.edu/software/netcdf/examples/sresa1b_ncar_ccsm3_0_run1_200001.nc
>> ");
>>
>> GridDatatype firstGridInfo = dataset.getGrids().get(0);
>>
>> System.out.println("Grid name ="+firstGridInfo.getName());
>>
>> GeoGrid firstGrid = (GeoGrid) dataset.getGrids().get(0);
>>
>>
>> System.out.println("WHOLE GRID");
>> GridCoordSystem gcs    = firstGrid.getCoordinateSystem();
>> System.out.println("is lat/lon system ? "+gcs.isLatLon());
>>
>> LatLonRect rect = gcs.getLatLonBoundingBox();
>> System.out.println("gcs bounding box : latmin="+rect.getLatMin()+"
>> latmax="+rect.getLatMax()+" lonmin="+rect.getLonMin()+"
>> lonmax="+rect.getLonMax());
>> System.out.println("projection       : "+gcs.getProjection());
>> System.out.println("width ="+gcs.getXHorizAxis().getSize()+",
>> height="+gcs.getYHorizAxis().getSize());
>> System.out.println("X is regular     ? "+((CoordinateAxis1D)
>> gcs.getXHorizAxis()).isRegular());
>> System.out.println("X is contiguous  ?
>> "+gcs.getXHorizAxis().isContiguous());
>> System.out.println("X start          : "+((CoordinateAxis1D)
>> gcs.getXHorizAxis()).getStart()) ;
>> System.out.println("X increment      : "+((CoordinateAxis1D)
>> gcs.getXHorizAxis()).getIncrement()) ;
>> System.out.println("Y is regular     ? "+((CoordinateAxis1D)
>> gcs.getYHorizAxis()).isRegular());
>> System.out.println("Y is contiguous  ?
>> "+gcs.getYHorizAxis().isContiguous());
>> System.out.println("Y start          : "+((CoordinateAxis1D)
>> gcs.getYHorizAxis()).getStart()) ;
>> System.out.println("Y increment      : "+((CoordinateAxis1D)
>> gcs.getYHorizAxis()).getIncrement()) ;
>>
>> LatLonPoint p = gcs.getLatLon(0,0);
>> System.out.println("index (0,0) --> lat/lon : "+p.getLatitude()+" ;
>> "+p.getLongitude());
>> p = gcs.getLatLon(1,1);
>> System.out.println("index (1,1) --> lat/lon : "+p.getLatitude()+" ;
>> "+p.getLongitude());
>>
>> System.out.println("looking up lat="+p.getLatitude()+"
>>  lon="+p.getLongitude());
>> int[] xy = gcs.findXYindexFromLatLon(p.getLatitude(), p.getLongitude(),
>> null);
>> System.out.println("index= ("+xy[0]+", "+xy[1]+")");
>>
>>
>> //
>> --------------------------------------------------------------------------
>> double latMin=-20.D, latMax=-10.D, lonMin=35.D, lonMax=45.D ;
>> System.out.println("\nSUBGRID (latmin="+latMin+"  latmax="+latMax+"
>>  lonmin="+lonMin+"  lonmax="+lonMax+")");
>>
>> LatLonRect    latLonRect = new LatLonRect(
>>                     new LatLonPointImpl(latMin, lonMin),
>>                     new LatLonPointImpl(latMax, lonMax)) ;
>>
>> GeoGrid   gridSubset = firstGrid.subset(null, null, latLonRect, 0, 1, 1) ;
>>
>> GridCoordSystem gcs2    = gridSubset.getCoordinateSystem();
>>
>> rect = gcs2.getLatLonBoundingBox();
>> System.out.println("is lat/lon system ? "+gcs2.isLatLon());
>> System.out.println("gcs bounding box : latmin="+rect.getLatMin()+"
>> latmax="+rect.getLatMax()+" lonmin="+rect.getLonMin()+"
>> lonmax="+rect.getLonMax());
>> System.out.println("projection       : "+gcs.getProjection());
>> System.out.println("width ="+gcs2.getXHorizAxis().getSize()+",
>> height="+gcs2.getYHorizAxis().getSize());
>> System.out.println("X is regular     ? "+((CoordinateAxis1D)
>> gcs2.getXHorizAxis()).isRegular());
>> System.out.println("X is contiguous  ?
>> "+gcs2.getXHorizAxis().isContiguous());
>> System.out.println("X start          : "+((CoordinateAxis1D)
>> gcs2.getXHorizAxis()).getStart()) ;
>> System.out.println("X increment      : "+((CoordinateAxis1D)
>> gcs2.getXHorizAxis()).getIncrement()) ;
>> System.out.println("Y is regular     ? "+((CoordinateAxis1D)
>> gcs2.getYHorizAxis()).isRegular());
>> System.out.println("Y is contiguous  ?
>> "+gcs2.getYHorizAxis().isContiguous());
>> System.out.println("Y start          : "+((CoordinateAxis1D)
>> gcs2.getYHorizAxis()).getStart()) ;
>> System.out.println("Y increment      : "+((CoordinateAxis1D)
>> gcs2.getYHorizAxis()).getIncrement()) ;
>>
>> p = gcs2.getLatLon(0,0);
>> System.out.println("index (0,0) --> lat/lon : "+p.getLatitude()+" ;
>> "+p.getLongitude());
>> p = gcs2.getLatLon(1,1);
>> System.out.println("index (1,1) --> lat/lon : "+p.getLatitude()+" ;
>> "+p.getLongitude());
>>
>> System.out.println("looking up lat="+p.getLatitude()+"
>>  lon="+p.getLongitude());
>> xy = gcs2.findXYindexFromLatLon(p.getLatitude(), p.getLongitude(), null);
>> System.out.println("index= ("+xy[0]+", "+xy[1]+")");
>>
>> } catch (IOException e) {
>> // TODO Auto-generated catch block
>> e.printStackTrace();
>> } catch (InvalidRangeException e) {
>> // TODO Auto-generated catch block
>> e.printStackTrace();
>> }
>>
>> _______________________________________________
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>>
>
>

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  • Re: [netcdf-java] Problem with findXYindexFromLatLon() on a Geogrid subset
    • From: franck . reinquin

• References:
  • [netcdf-java] Problem with findXYindexFromLatLon() on a Geogrid subset
    • From: franck . reinquin
  • Re: [netcdf-java] Problem with findXYindexFromLatLon() on a Geogrid subset
    • From: John Caron