[gradsusr] 回復: How to read latitude/longitude data from background map

[yaqiang.wang at gmail.com]

The following is Java code to read GrADS map data, which should be useful for understanding the format.

String fileName = "../hires"
DataInputStream br = new DataInputStream(new BufferedInputStream(new FileInputStream(new File(fileName))));
int i, lineNum; 
byte b; 
short N, lType; 
double lon, lat; 
byte[] bytes;

lineNum = 0; 
do { 
    b = br.readByte(); // 1-data, 2-skip 
    if ("2".equals(Byte.toString(b))) { 
        br.skipBytes(18); 
        continue; 
    } 
    b = br.readByte(); // Line type: country, river ... 
    lType = (short) DataConvert.byte2Int(b); 
    b = br.readByte(); // Point number 
    N = (short) DataConvert.byte2Int(b); 
    for (i = 0; i < N; i++) { 
        bytes = new byte[3]; 
        br.read(bytes); //Longitude 
        int val = 0; 
        for (int bb = 0; bb < 3; bb++) { 
            val <<= 8; 
            val |= (int) bytes[bb] & 0xFF; 
        } 
        lon = val / 10000.0; 

        bytes = new byte[3]; 
        br.read(bytes); //Latitude 
        val = 0; 
        for (int bb = 0; bb < 3; bb++) { 
            val <<= 8; 
            val |= (int) bytes[bb] & 0xFF; 
        } 
        lat = val / 10000.0 - 90.0; 
    } 

    lineNum++; 
} while (br.available() > 0); 

br.close();

Regards
Yaqiang


*************************************************
Dr. Yaqiang Wang
Chinese Academy of Meteorological Sciences (CAMS)
46, Zhong-Guan-Cun South Avenue
Beijing, 100081
China
　　　　　　　　　　　　　
yaqiang.wang at gmail.com

http://www.meteothinker.com
**************************************************
 
發件人： Tsai Ray
發送時間： 2014-08-15 03:06
收件人： gradsusr at gradsusr.org
主題： [gradsusr] How to read latitude/longitude data from background map
Dear GrASD users,

I already have a high-resolution regional backgruond map data(same formation as hires and lowres), and

now I'm trying to read the latitude/longitude from it by fortran program.

But I'm not sure about the formation of background map data, and still can't get the correct latitude/longitude information.

Is there any way to solve this problem, please~~~~


Thanks,

Ray
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