使用C++对himawari8（9）卫星数据的读取

        本人刚学C/C++不到半年，然后想用C++来写点东西，于是便有了本文的内容。 

himawari 系列卫星

        himawari8是日本发射的在西太平洋赤道上空的新一代静止轨道气象卫星，配备了16个不同的波段和5个观测区（1：FLDK圆盘，2:JP日本区域高频，3：目标观测区，台风吧常称为机动观测区，4：校准用高频区，不开放，5：未开放高频区）可用于多种观测，本文主要提到的是第8号和第9号所用的HSD格式卫星数据。

        数据可以在JAXA Himawari Monitor | Registration申请访问。

前期准备

        要想读取文件那首先得了解结构。数据使用指南在以下链接可以下载：https://www.data.jma.go.jp/mscweb/en/himawari89/space_segment/hsd_sample/HS_D_users_guide_en_v13.pdfhttps://www.data.jma.go.jp/mscweb/en/himawari89/space_segment/hsd_sample/HS_D_users_guide_en_v13.pdf        HSD为二进制存储的数据文件，文件分为12个块。块1：基本信息，块2：数据信息，块3：投影信息，块4：导航信息，块5：校准信息，块6：校准间信息，块7：段信息，块8：导航校正信息，块9：观测时间信息，块10：错误信息，块11：空白块，块12：数据，这里就不展开赘述。

程序设计

        处理信息头的时候我们将先使用结构体来定义11个块。

typedef struct{
	unsigned char	BlockNum;
	unsigned short	BlockLen;
	unsigned short	HeaderNum;
	char			ByteOrder;
	char			SatName[17];
	char			ProName[17];
	char			ObsType1[5];
	char			ObsType2[3];
	unsigned short	TimeLine;
	double			ObsStartTime;
	double			ObsEndTime;
	double			FileCreationMjd;
	unsigned		HeaderLen;
	unsigned		DataLen;
	unsigned char	qflag1;
	unsigned char	qflag2;
	unsigned char	qflag3;
	unsigned char	qflag4;
	char			DataVer[33];
	char			FileName[129];
	char			Spare[41];
}  Basic_info;

typedef struct{
	unsigned char	BlockNum;
	unsigned short	BlockLen;
	unsigned short	BitPix;
	unsigned short	nPix;
	unsigned short	nLin;
	unsigned char	comp;
	char			Spare[41];
}Data_info;

typedef struct{
	unsigned char	BlockNum;
	unsigned short	BlockLen;
	double			subLon;
	unsigned		cfac;
	unsigned		lfac;
	float			coff;
	float			loff;
	double			SatDis;
	double			eqtrRadius;
	double			polrRadius;
	double			projParam1;
	double			projParam2;
	double			projParam3;
	double			projParamSd;
	unsigned short	resampleKind;
	unsigned short	resampleSize;
	char			Spare[41];
} Proj_info;

typedef struct{
	unsigned char	BlockNum;
	unsigned short	BlockLen;
	double			navMjd;
	double			sspLon;
	double			sspLat;
	double			SatDis;
	double			nadirLon;
	double			nadirLat;
	double			SunPos_X;
	double			SunPos_Y;
	double			SunPos_Z;
	double			MoonPos_X;
	double			MoonPos_Y;
	double			MoonPos_Z;
	char			Spare[41];
} Navi_info;

typedef struct {
	unsigned char	BlockNum;
	unsigned short	BlockLen;
	unsigned short	Band;
	double			waveLen;
	unsigned short	bitPix;
	unsigned short	ErrorCount;
	unsigned short	OutCount;
	double			gain_cnt2rad;
	double			cnst_cnt2rad;
	double			rad2btp_c0;
	double			rad2btp_c1;
	double			rad2btp_c2;
	double			rad2btp_c3;
	double			btp2rad_c0;
	double			btp2rad_c1;
	double			btp2rad_c2;
	double			c;	//光速 lightSpeed
	double			h;	//普朗克常数 planckConst
	double			p;	//黑体常数 bolzConst
	double			Spare[41];
	double			rad2albedo;
	double			Coeff_mjd;
	double			gain_cnt2rad_mod;
	double			cnst_cnt2rad_mod;
	char			SpareV[105];
} Calib_info;

typedef struct{
	unsigned char	BlockNum;
	unsigned short	BlockLen;
	double			gsicsCorr_C;
	double			gsicsCorr_C_er;
	double			gsicsCorr_1;
	double			gsicsCorr_1_er;
	double			gsicsCorr_2;
	double			gsicsCorr_2_er;
	double			gsicsBias;
	double			gsicsUncert;
	double			gsicsStscene;
	double			gsicsCorr_StrMJD;
	double			gsicsCorr_EndMJD;
	char			gsicsCorrInfo[65];
	float			gsicsUpperLimit;
	float			gsicsLowerLimit;
	char			gsicsFilename[129];
	char			Spare[129];
} InterCalib_info;

typedef struct{
	unsigned char	BlockNum;
	unsigned short	BlockLen;
	char			totalSegNum;
	char			segSeqNo;
	unsigned short	strLineNo;
	char			Spare[41];
} Segm_info;

typedef struct{
	unsigned char	BlockNum;
	unsigned short	BlockLen;
	float			RoCenterColumn;		
	float			RoCenterLine;		
	double			RoCorrection;		
	unsigned short	correctNum;		
	unsigned short* lineNo;			
	float*			columnShift;	
	float*			lineShift;	
	char			Spare[41];		

} NaviCorr_info;

typedef struct{
	unsigned char	BlockNum;
	unsigned short	BlockLen;
	unsigned short	obsNum;
	unsigned short* lineNo;
	double*			obsMJD;
	char			Spare[41];
} ObsTime_info;

typedef struct{
	unsigned char	BlockNum;
	unsigned int	BlockLen;
	unsigned short	errorNum;
	unsigned short* lineNo;
	unsigned short* errPixNum;
	char			Spare[41];
} Erro_info;

typedef struct{
	unsigned char	BlockNum;
	unsigned short	BlockLen;
	char			Spare[257];
} Spare;

        随后我们使用一个类进行封装：

using namespace std;

class HSD
{private:
    FILE* fp;
    double planck_c1, planck_c2, lambda, effective_temperature, phi, re, r1, r2, r3, rn,     x, y, Sd, Sn, S1, S2, S3, Sxy;
    char byteFlag;
    bool ER_FLAG,Read_State;
	float c, l, version;
    int byteOrder(void) {
		int i = 1;
		if (*((char*)&i)) return 0;	/*  Little */
		else if (*((char*)&i + (sizeof(int) - 1))) return 1; /* Big */
		else return -1;
	}

    void swapBytes(void* buf, int size, int nn){
    	char* ba, * bb, * buf2;
    	buf2 = (char*)buf;
	    while (nn--) {
		    bb = (ba = buf2) + size - 1;
		    do {
		    	char a;
		    	a = *ba;
		    	*ba = *bb;
		    	*bb = a;
		    } while (++ba < --bb);
		    buf2 += size;
    	}
    }
public:
	Basic_info		basic;
	Data_info		data;
	Proj_info		proj;
	Navi_info		nav;
	Calib_info		calib;
	InterCalib_info interCalib;
	Segm_info		seg;
	NaviCorr_info	navcorr;
	ObsTime_info	obstime;
	Erro_info		error;
	Spare			spare;
	Correct_Table	correct_table;
    
    bool ReadData(char* filename);
    bool lonlat_topixlin(double lon, double lat, double & pix, double & lin);
    bool pixlin_to_lonlat( float pix, float lin, double & lon, double & lat);
	double RadianceToTBB(unsigned short radiance);
	double RadianceToReflectivity(unsigned short radiance);
};

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