ucar.nc2.dt.grid.gis.GridBoundariesExtractor Maven / Gradle / Ivy
/*
* Copyright 1998-2014 University Corporation for Atmospheric Research/Unidata
*
* Portions of this software were developed by the Unidata Program at the
* University Corporation for Atmospheric Research.
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package ucar.nc2.dt.grid.gis;
import java.util.ArrayList;
import java.util.List;
import ucar.nc2.dataset.CoordinateAxis1D;
import ucar.nc2.dataset.CoordinateAxis2D;
import ucar.nc2.dt.GridCoordSystem;
import ucar.nc2.dt.GridDataset;
import ucar.nc2.dt.GridDataset.Gridset;
import ucar.unidata.geoloc.LatLonPoint;
import ucar.unidata.geoloc.ProjectionImpl;
/**
*
* Provides methods for extracting the grid boundaries in standard GIS text formats: WKT and GeoJSON
*
* @author mhermida
*
*/
public final class GridBoundariesExtractor {
private GridDataset gridDataset;
private double minLon=0;
private double maxLon=0;
private double maxDiff =0;
private boolean crossesDateLine = false;
private GridBoundariesExtractor(){}
private GridBoundariesExtractor(GridDataset gridDataset){
this.gridDataset = gridDataset;
}
/**
*
* Takes a GridDataset and returns the boundary for the first gridset in the dataset in as a polygon in WKT
*
*
* @return WKT
*/
public String getDatasetBoundariesWKT(){
StringBuilder polygonWKT = new StringBuilder( "POLYGON((");
List polLons = new ArrayList<>();
List polLats = new ArrayList<>();
getLatLonsForPolygon(polLons, polLats );
//Build string from lists
//Crosses dateLine?
//Assuming grid cells don't extend more than 270 deg.
if( (maxLon > 0 && minLon < 0) && maxDiff > 270 ){
//either crosses 0 or -180
crossesDateLine = true;
}
int nPoints = polLats.size();
for( int i=0; i< nPoints; i++ ){
double lon = polLons.get(i);
if(crossesDateLine && lon < 0) lon+=360;
if(i < nPoints -1)
polygonWKT.append( lon ).append(" ").append( polLats.get(i) ).append(",");
else
polygonWKT.append( lon ).append(" ").append( polLats.get(i) );
}
polygonWKT.append("))");
return polygonWKT.toString();
}
public String getDatasetBoundariesGeoJSON(){
StringBuilder polygonJSON = new StringBuilder( "{\"type\":\"Polygon\", \"coordinates\":[ [ " );
List polLons = new ArrayList<>();
List polLats = new ArrayList<>();
getLatLonsForPolygon(polLons, polLats );
//Build string from lists
//Crosses dateLine?
//Assuming grid cells don't extend more than 270 deg.
if( (maxLon > 0 && minLon < 0) && maxDiff > 270 ){
//either crosses 0 or -180
crossesDateLine = true;
}
int nPoints = polLats.size();
for( int i=0; i< nPoints; i++ ){
double lon = polLons.get(i);
if(crossesDateLine && lon < 0) lon+=360;
if(i < nPoints -1)
polygonJSON.append("[").append( lon ).append(", ").append( polLats.get(i) ).append("],");
else
polygonJSON.append("[").append( lon ).append(", ").append( polLats.get(i) ).append("]");
}
polygonJSON.append(" ] ]}");
return polygonJSON.toString();
}
private void getLatLonsForPolygon( List polLons, List polLats){
Gridset gridset = gridDataset.getGridsets().get(0);
GridCoordSystem coordSystem = gridset.getGeoCoordSystem();
ProjectionImpl fromProj = coordSystem.getProjection();
coordSystem.getLatLonBoundingBox();
if( coordSystem.getYHorizAxis() instanceof CoordinateAxis1D && coordSystem.getXHorizAxis() instanceof CoordinateAxis1D ){
CoordinateAxis1D xAxis = (CoordinateAxis1D) coordSystem.getXHorizAxis();
CoordinateAxis1D yAxis =(CoordinateAxis1D) coordSystem.getYHorizAxis();
if(coordSystem.isGlobalLon()) {
double maxy = yAxis.getMaxValue();
double miny = yAxis.getMinValue();
polLons.add(0.0);
polLats.add(miny);
polLons.add(360.0);
polLats.add(miny);
polLons.add(360.0);
polLats.add(maxy);
polLons.add(0.0);
polLats.add(maxy);
polLons.add(0.0);
polLats.add(miny);
//polygonWKT.append("-180 "+ miny +", 180 "+ miny +", 180 "+ maxy +", -180 "+ maxy +", -180 "+ miny +"] ))");
//polygonWKT.append("0 "+ miny +", 360 "+ miny +", 360 "+ maxy +", 0 "+ maxy +", 0 "+ miny +"] ))");
//return polygonWKT.toString();
}else{
double[] xCoords = xAxis.getCoordValues();
double[] yCoords = yAxis.getCoordValues();
LatLonPoint prev = fromProj.projToLatLon(xCoords[0], yCoords[0]);
//Bottom edge
for( double x : xCoords ){
LatLonPoint point = fromProj.projToLatLon(x, yCoords[0]);
if( point.getLongitude() < minLon ) minLon = point.getLongitude();
if( point.getLongitude() > maxLon ) maxLon = point.getLongitude();
if( Math.abs(prev.getLongitude() - point.getLongitude() ) > maxDiff )
maxDiff = Math.abs(prev.getLongitude() - point.getLongitude() );
polLons.add(point.getLongitude());
polLats.add(point.getLatitude());
prev = point;
}
//Right edge
for( double y : yCoords ){
LatLonPoint point = fromProj.projToLatLon(xCoords[xCoords.length-1], y);
if( point.getLongitude() < minLon ) minLon = point.getLongitude();
if( point.getLongitude() > maxLon ) maxLon = point.getLongitude();
if( Math.abs(prev.getLongitude() - point.getLongitude() ) > maxDiff )
maxDiff = Math.abs(prev.getLongitude() - point.getLongitude() );
polLons.add(point.getLongitude());
polLats.add(point.getLatitude());
prev = point;
}
//Top
for( int i = xCoords.length-1; i>=0; i-- ){
LatLonPoint point = fromProj.projToLatLon(xCoords[i], yCoords[yCoords.length-1]);
if( point.getLongitude() < minLon ) minLon = point.getLongitude();
if( point.getLongitude() > maxLon ) maxLon = point.getLongitude();
if( Math.abs(prev.getLongitude() - point.getLongitude() ) > maxDiff )
maxDiff = Math.abs(prev.getLongitude() - point.getLongitude() );
polLons.add(point.getLongitude());
polLats.add(point.getLatitude());
prev = point;
}
//Left edge
for( int i = yCoords.length-1; i>=0; i-- ){
LatLonPoint point = fromProj.projToLatLon(xCoords[0], yCoords[i]);
if( point.getLongitude() < minLon ) minLon = point.getLongitude();
if( point.getLongitude() > maxLon ) maxLon = point.getLongitude();
if( Math.abs(prev.getLongitude() - point.getLongitude() ) > maxDiff )
maxDiff = Math.abs(prev.getLongitude() - point.getLongitude() );
polLons.add(point.getLongitude());
polLats.add(point.getLatitude() );
prev = point;
}
}
}else if( coordSystem.getYHorizAxis() instanceof CoordinateAxis2D && coordSystem.getXHorizAxis() instanceof CoordinateAxis2D ){
//Get boundaries from 2d axis...
CoordinateAxis2D xAxis = (CoordinateAxis2D) coordSystem.getXHorizAxis();
CoordinateAxis2D yAxis =(CoordinateAxis2D) coordSystem.getYHorizAxis();
int[] xShape = xAxis.getShape();
int[] yShape = yAxis.getShape();
LatLonPoint prev = fromProj.projToLatLon(xAxis.getCoordValue(0, 0), yAxis.getCoordValue(0, 0));
for(int i = 0; i < xShape[0]; i++ ){
double x = xAxis.getCoordValue(i, 0);
double y = yAxis.getCoordValue(i, 0);
LatLonPoint point = fromProj.projToLatLon(x, y);
if( point.getLongitude() < minLon ) minLon = point.getLongitude();
if( point.getLongitude() > maxLon ) maxLon = point.getLongitude();
if( Math.abs(prev.getLongitude() - point.getLongitude() ) > maxDiff )
maxDiff = Math.abs(prev.getLongitude() - point.getLongitude() );
polLons.add(point.getLongitude());
polLats.add(point.getLatitude());
prev = point;
}
for(int i = 0; i < xShape[1]; i++ ){
double x = xAxis.getCoordValue(xShape[0]-1, i);
double y = yAxis.getCoordValue(xShape[0]-1, i);
LatLonPoint point = fromProj.projToLatLon(x, y);
if( point.getLongitude() < minLon ) minLon = point.getLongitude();
if( point.getLongitude() > maxLon ) maxLon = point.getLongitude();
if( Math.abs(prev.getLongitude() - point.getLongitude() ) > maxDiff )
maxDiff = Math.abs(prev.getLongitude() - point.getLongitude() );
polLons.add(point.getLongitude());
polLats.add(point.getLatitude());
prev = point;
}
for(int i = xShape[0]-1 ; i >= 0; i-- ){
double x = xAxis.getCoordValue(i, xShape[1]-1);
double y = yAxis.getCoordValue(i, xShape[1]-1);
LatLonPoint point = fromProj.projToLatLon(x, y);
if( point.getLongitude() < minLon ) minLon = point.getLongitude();
if( point.getLongitude() > maxLon ) maxLon = point.getLongitude();
if( Math.abs(prev.getLongitude() - point.getLongitude() ) > maxDiff )
maxDiff = Math.abs(prev.getLongitude() - point.getLongitude() );
polLons.add(point.getLongitude());
polLats.add(point.getLatitude());
prev = point;
}
for(int i = xShape[1]-1 ; i >= 0; i-- ){
double x = xAxis.getCoordValue(0, i);
double y = yAxis.getCoordValue(0, i);
LatLonPoint point = fromProj.projToLatLon(x, y);
if( point.getLongitude() < minLon ) minLon = point.getLongitude();
if( point.getLongitude() > maxLon ) maxLon = point.getLongitude();
if( Math.abs(prev.getLongitude() - point.getLongitude() ) > maxDiff )
maxDiff = Math.abs(prev.getLongitude() - point.getLongitude() );
polLons.add(point.getLongitude());
polLats.add(point.getLatitude());
prev = point;
}
}
}
public static GridBoundariesExtractor valueOf(GridDataset gds){
return new GridBoundariesExtractor(gds);
}
}
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