气象NC扇形经纬网格转换成前端要求的等经纬网格

气象NC扇形经纬网格转换成前端leaflet-vector-scalar.js要求的等经纬网格
背景：最近从气象局拿到文件格式为NC的气象文件(包括温度、湿度、风、气压、雨量等)，需要读取其中的温度数据并在前端展示。用专业软件打开一看，图是扇形的，经纬度间隔也不相等,如下图：

问题：需要读文件格式为NC的气象文件中的温度数据，并转换为leaflet-vector-scalar.js要求的等经纬网格JSON数据。
解决：通过JAVA调用netcdf包读取NC文件，将NC扇形经纬网格转换成等经纬网格，转换思路如下：
将扇形经纬网格1、2、3、4(红色格)数值相加求平均值，赋值给等经纬网格a(黑色格)实现JAVA代码如下：

import java.io.File;
import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Date;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import ucar.ma2.ArrayFloat;
import ucar.ma2.DataType;
import ucar.nc2.*;public class CreateNetCDF_2D_TEMP {public final static float MISSING_VALUE = -9.96921E36f;public final static String TMP_DIR = "D:/";public static void main(String[] args) throws Exception {//last 'aa' is 'AM' or 'PM'. 'HH' is 24 hour system. if you change it to 'hh', it means 12 hour systemSimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss aa");NetcdfFile ncfile = null;NetcdfFileWriter writer = null;//自定义等间距网格数int xGridsNum = 350;int yGridsNum = 300;try {ncfile = NetcdfFile.open("d:/temp.nc");// Get the latitude and longitude Variables.Variable latVarO = ncfile.findVariable("NLAT");Variable lonVarO = ncfile.findVariable("ELON");// Get the temperature Variables.Variable tmpVariable = ncfile.findVariable("TMP");ArrayFloat.D2 latArray;ArrayFloat.D2 lonArray;ArrayFloat.D2 tmpArray;latArray = (ArrayFloat.D2) latVarO.read();lonArray = (ArrayFloat.D2) lonVarO.read();tmpArray = (ArrayFloat.D2) tmpVariable.read();//Calculate latitude and longitude rangefloat minLat = 99999f, maxLat = 0f;float minLon = 99999f, maxLon = 0f;int latGridsNumO = latVarO.getDimension(0).getLength();int lonGridsNumO = latVarO.getDimension(1).getLength();//使用原始NC数据中网格数//xGridsNum = latGridsNumO;//yGridsNum = lonGridsNumO;//Calculate temperature rangefloat minTmp = 99999f, maxTmp = 0f;for(int j=0;j<lonGridsNumO;j++) {for(int i=0; i<latGridsNumO; i++) {float fLat = latArray.get(i,j);float fLon = lonArray.get(i,j);float fTemp = tmpArray.get(i,j);//latData.set(i,j, f);//lonData.set(i,j, f);if(maxLat<fLat) maxLat = fLat;if(minLat>fLat) minLat = fLat;if(maxLon<fLon) maxLon = fLon;if(minLon>fLon) minLon = fLon;if(maxTmp<fTemp) maxTmp = fTemp;if(minTmp>fTemp) minTmp = fTemp;}}System.out.println("lo1:" + minLon);System.out.println("lo2:" + maxLon);System.out.println("la1:" + maxLat);System.out.println("la2:" + minLat);System.out.println("nx:" + xGridsNum);System.out.println("ny:" + yGridsNum);System.out.println("minTEMP:" + minTmp);System.out.println("maxTEMP:" + maxTmp);//定义新的NC文件String varname = "temp0";writer = NetcdfFileWriter.createNew(NetcdfFileWriter.Version.netcdf3, TMP_DIR+varname+".nc");//经度纬度维度定义Dimension latDimension = writer.addDimension(null, "lat", yGridsNum);Dimension lonDimension = writer.addDimension(null, "lon", xGridsNum);//纬度变量属性设置Variable latVar = writer.addVariable(null, "lat", DataType.FLOAT, Arrays.asList(lonDimension,latDimension));latVar.addAttribute(new Attribute("units", "Degrees_north"));latVar.addAttribute(new Attribute("description", "Latitude"));latVar.addAttribute(new Attribute("long_name", "Latitude"));latVar.addAttribute(new Attribute("standard_name", "latitude"));latVar.addAttribute(new Attribute("axis", "Y"));latVar.addAttribute(new Attribute("coordinate_defines", "center"));latVar.addAttribute(new Attribute("actual_range",Arrays.asList(minLat, maxLat)));//经度变量属性设置Variable lonVar = writer.addVariable(null, "lon", DataType.FLOAT, Arrays.asList(lonDimension,latDimension));lonVar.addAttribute(new Attribute("units", "Degrees_east"));lonVar.addAttribute(new Attribute("description", "Longitude"));lonVar.addAttribute(new Attribute("long_name", "Longitude"));lonVar.addAttribute(new Attribute("standard_name", "longitude"));lonVar.addAttribute(new Attribute("axis", "X"));lonVar.addAttribute(new Attribute("coordinate_defines", "center"));lonVar.addAttribute(new Attribute("actual_range",Arrays.asList(minLon, maxLon)));//温度变量属性设置Variable tempVar = writer.addVariable(null, varname, DataType.FLOAT, Arrays.asList(lonDimension,latDimension));tempVar.addAttribute(new Attribute("units", "degK"));tempVar.addAttribute(new Attribute("description", "Temperature temp"));tempVar.addAttribute(new Attribute("missing_value", MISSING_VALUE));tempVar.addAttribute(new Attribute("dataset", "NOAA/NCEP GHCN CAMS"));tempVar.addAttribute(new Attribute("var_desc", "Air Temperature"));tempVar.addAttribute(new Attribute("valid_range", Arrays.asList(150.0f,400.0f)));//add global attributeswriter.addGroupAttribute(null, new Attribute("SOUTH-NORTH_GRID_DIMENSION", latDimension.getLength()));writer.addGroupAttribute(null, new Attribute("WEST-EAST_GRID_DIMENSION", lonDimension.getLength()));writer.addGroupAttribute(null, new Attribute("TITLE", "NOAA/NCEP GHCN CAMS Monthly Temperature"));writer.addGroupAttribute(null, new Attribute("Conventions", "CF-1.0"));//定义新NC文件中经度、纬度、温度变量数组ArrayFloat.D2 latData = new ArrayFloat.D2(lonDimension.getLength(), latDimension.getLength());ArrayFloat.D2 lonData = new ArrayFloat.D2(lonDimension.getLength(), latDimension.getLength());ArrayFloat.D2 tempData = new ArrayFloat.D2(lonDimension.getLength(), latDimension.getLength());//纬度网格间距float latLen = Math.abs(maxLat-minLat)/latDimension.getLength();//经度网格间距float lonLen = Math.abs(maxLon-minLon)/lonDimension.getLength();System.out.println("dy:" + latLen);System.out.println("dx:" + lonLen);//创建一个线程池ExecutorService pool = Executors.newCachedThreadPool();for(int j=0; j<latDimension.getLength(); j++) {for(int i=0; i<lonDimension.getLength(); i++) {float tempLat = minLat + j*latLen;float tempLon = minLon + i*lonLen;latData.set(i,j, tempLat);lonData.set(i,j, tempLon);//Date date0 = new Date();//System.out.println("线程" + i + "," + j + "开启时间" + sdf.format(date0));//计算等经纬网格中J，I网格的值Callable c = new MyCallable(latGridsNumO,lonGridsNumO,latArray,lonArray,tmpArray,tempLat,tempLon,latLen,lonLen);//执行任务并获取 Future 对象Future future = pool.submit(c);float f = Float.parseFloat(future.get().toString());tempData.set(i,j, f);}}tempVar.addAttribute(new Attribute("actual_range", Arrays.asList(minTmp, maxTmp)));// 关闭线程池pool.shutdown();//将数组中的数据组装成字符串。数据之间','间隔String TEMPData = "";for(int j=latDimension.getLength()-1;j>-1;j--){for(int i=0;i<lonDimension.getLength();i++) {if(j==0&&i==lonDimension.getLength()-1){TEMPData += tempData.get(i,j) + "";}else{TEMPData += tempData.get(i,j) + ",";}}}//将温度数据写入txtFile file = new File("d:\\outTmp.txt"); //存放数组数据的文件java.io.FileWriter out = new  java.io.FileWriter(file); //文件写入流out.write(TEMPData);out.close();//创建新的NC文件，并写入值writer.create();writer.write(latVar, latData);writer.write(lonVar, lonData);writer.write(tempVar, tempData);//打印温度值总数量System.out.println("Temperature value number:" + tempData.getSize());//System.out.println(tempData.get(tempData.getSize()-1).toString());writer.close();//前端需要返回的参数
//          float lo1 = minLon;
//          float lo2 = maxLon;
//          float la1 = maxLat;
//          float la2 = minLat;
//          int nx = xGridsNum;
//          int ny = yGridsNum;
//          float dy = latLen;
//          float dx = lonLen;
//          String data = TEMPData;
//          float minTEMP = minTmp;
//          float maxTEMP = maxTmp;} finally {ncfile.close();}}}class MyCallable implements Callable<Object> {//参数定义int latGridsNumO;int lonGridsNumO;ArrayFloat.D2 latArray;ArrayFloat.D2 lonArray;ArrayFloat.D2 tmpArray;float tempLat;float tempLon;float latLen;float lonLen;MyCallable(int latGridsNumO,int lonGridsNumO,ArrayFloat.D2 latArray,ArrayFloat.D2 lonArray,ArrayFloat.D2 tmpArray,float tempLat,float tempLon,float latLen,float lonLen) {this.latGridsNumO = latGridsNumO;this.lonGridsNumO = lonGridsNumO;this.latArray = latArray;this.lonArray = lonArray;this.tmpArray = tmpArray;this.tempLat = tempLat;this.tempLon = tempLon;this.latLen = latLen;this.lonLen = lonLen;}public Object call() throws Exception {float tempTmps = 0f;int tempNum = 0;for(int jLat=0; jLat<this.lonGridsNumO; jLat++) {for (int iLon = 0; iLon < this.latGridsNumO; iLon++) {if(this.latArray.get(iLon,jLat)>=(tempLat-latLen) &&this.latArray.get(iLon,jLat)<=(tempLat+latLen) &&this.lonArray.get(iLon,jLat)>=(tempLon-lonLen) &&this.lonArray.get(iLon,jLat)<=(tempLon+lonLen)){tempNum++;tempTmps += this.tmpArray.get(iLon,jLat);}}}float f = 0f;if(tempNum>0){f = tempTmps/tempNum;}return f;}
}

最终leaflet-vector-scalar.js展示结果如下：

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气象NC扇形经纬网格转换成前端要求的等经纬网格

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