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rtklib学习——读取观测文件和导航电文

萌宠菠菠乐园
2025-07-20 10:06

rinex文件放在一起读取，主要是分为头部和body两部分读取。opt为prcopt->rnxopt[2][256] (rinex options {rover,base})

头文件读取(END OF HEADE标识作为收尾)

RINEX VERSION / TYPE:类型ver、格式type、系统sys、时间tsys

通过不同的读取文件格式进入子函数内（重点分析O和N，遇到c文件直接跳出头文件读取）

switch (*type) {

case 'O': decode_obsh(fp,buff,*ver,tsys,tobs,nav,sta); break;

case 'N': decode_navh (buff,nav); break;

case 'G': decode_gnavh(buff,nav); break;

case 'H': decode_hnavh(buff,nav); break;

case 'J': decode_navh (buff,nav); break;

case 'L': decode_navh (buff,nav); break;

}

观测文件（decode_obsh）

观测值信息存入此结构体内

typedef struct { /* station parameter type */

char name [MAXANT]; /* marker name */

char marker [MAXANT]; /* marker number */

char antdes [MAXANT]; /* antenna descriptor */

char antsno [MAXANT]; /* antenna serial number */

char rectype[MAXANT]; /* receiver type descriptor */

char recver [MAXANT]; /* receiver firmware version */

char recsno [MAXANT]; /* receiver serial number */

int antsetup; /* antenna setup id */

int itrf; /* ITRF realization year */

int deltype; /* antenna delta type (0:enu,1:xyz) */

double pos[3]; /* station position (ecef) (m) */

double del[3]; /* antenna position delta (e/n/u or x/y/z) (m) */

double hgt; /* antenna height (m) */

int glo_cp_align; /* GLONASS code-phase alignment (0:no,1:yes) */

double glo_cp_bias[4]; /* GLONASS code-phase biases {1C,1P,2C,2P} (m) */

} sta_t;

接收机名字name、编号marker、列号recsno、类型rectype、版本号recver、天线序列号antsno、天线类型antdes、接收机近似坐标pos、天线中心相对于天线标志位的下表面高度东向北向的偏心del、时间系统tsys、跳秒数nav->utc_gps。GLONASS略

重点在于读取观测类型char tobs[][MAXOBSTYPE][4]，只考虑rinex3以上的版本。

C 28 C1X C2I C5X C6I C7I C7Z C8X D1X D2I D5X D6I D7I D7Z SYS / # / OBS TYPES
D8X L1X L2I L5X L6I L7I L7Z L8X S1X S2I S5X S6I S7I SYS / # / OBS TYPES
S7Z S8X SYS / # / OBS TYPES

用于修改观测类型第三位不能读取问题——frqcodes[]="1256789"和*defcodes[]={ "CWX ", GPS: L125____ "CCXX X ", GLO: L1234_6_ "C XXXX ", GAL: L1_5678_,"CXXX ", QZS: L1256___ "C X ", SBS: L1_5____ "XIXIIX ", BDS: L125678_ " A A" IRN: L__5___9 。

tobs[i][MAXOBSTYPE][4]中 i：系统； MAXOBSTYPE：观测数目，最大读取64，上例读取28； [4]：型号，例如C1X。tobs[5][0][0]表示北斗的第一个观测类型的第一个元素C。tobs[5][0]表示C1X。

在3.02版本中对北斗观测类型修改，x1x变为x2x

if (!(p=strchr(syscodes,buff[0]))) {

trace(2,"invalid system code: sys=%cn",buff[0]);

return;

}

i=(int)(p-syscodes); //属于什么系统

n=(int)str2num(buff,3,3);

for (j=nt=0,k=7;j<n;j++,k+=4) {

if (k>58) {

if (!fgets(buff,MAXRNXLEN,fp)) break;

k=7;

}

if (nt<MAXOBSTYPE-1) setstr(tobs[i][nt++],buff+k,3); /* 观测类型，i代表不同的系统，nt为不同的频点,后面的表示频点的字符组成如c1c */

}

*tobs[i][nt]='';

/* change BDS B1 code: 3.02 */

if (i==5&&fabs(ver-3.02)<1e-3) {

for (j=0;j<nt;j++) if (tobs[i][j][1]=='1') tobs[i][j][1]='2';

}

/* if unknown code in ver.3, set default code */

for (j=0;j<nt;j++) {

if (tobs[i][j][2]) continue;

if (!(p=strchr(frqcodes,tobs[i][j][1]))) continue;

tobs[i][j][2]=defcodes[i][(int)(p-frqcodes)];

trace(2,"set default for unknown code: sys=%c code=%sn",buff[0],

tobs[i][j]);

}

导航电文

IONOSPHERIC CORR_____各个系统的电离层参数nav->ion_gps/gal/qzs.....

TIME SYSTEM CORR_____GNSS系统时间与UTC或其他时间系统的差异nav->utc_gps/glo/gal......

LEAP SECONDS_________跳秒时间差nav->utc_gps

body部分读取(END OF HEADE标识作为收尾)

观测文件

信号索引读取，设置信号的tobs读取顺序、频点、优先级及优先级

typedef struct { /* signal index type */
int n; /* number of index */
int idx[MAXOBSTYPE]; /* signal freq-index */
int pos[MAXOBSTYPE]; /* signal index in obs data (-1:no) */
uint8_t pri [MAXOBSTYPE]; /* signal priority (15-0) */
uint8_t type[MAXOBSTYPE]; /* type (0:C,1:L,2:D,3:S) */
uint8_t code[MAXOBSTYPE]; /* obs-code (CODE_L??) */
double shift[MAXOBSTYPE]; /* phase shift (cycle) */
} sigind_t;

1.索引代码段（set_index）

for (i=n=0;*tobs[i];i++,n++) { /*存储的是观测值类型，CIC、C1W 在obscodes什么位置上*/

ind->code[i]=obs2code(tobs[i]+1); /*code存储的是观测值频率信号通道类型，映射为频率。L1、L2、L3、L4 code为在什么位置*/

ind->type[i]=(p=strchr(obscodes,tobs[i][0]))?(int)(p-obscodes):0; /*观测值类型0伪距1载波2多普勒3载噪比*/

ind->idx[i]=code2idx(sys,ind->code[i]); /*频点索引，记录频点信息，例如L1/L2/L3/L4*/

ind->pri[i]=getcodepri(sys,ind->code[i],opt); /*频率编号优先级，返回*/

ind->pos[i]=-1; /*有效标志位,先全部无效-1，后面优先级用哪个*/

}

static char *obscodes[]={ /* observation code strings */

"" ,"1C","1P","1W","1Y", "1M","1N","1S","1L","1E", /* 0- 9 */

"1A","1B","1X","1Z","2C", "2D","2S","2L","2X","2P", /* 10-19 */

"2W","2Y","2M","2N","5I", "5Q","5X","7I","7Q","7X", /* 20-29 */

"6A","6B","6C","6X","6Z", "6S","6L","8L","8Q","8X", /* 30-39 */

"2I","2Q","6I","6Q","3I", "3Q","3X","1I","1Q","5A", /* 40-49 */

"5B","5C","9A","9B","9C", "9X","1D","5D","5P","5Z", /* 50-59 */

"6E","7D","7P","7Z","8D", "8P","4A","4B","4X","" /* 60-69 */

};

优先级顺序codeepris中的[7][MAXFREQ][16] 15为最高优先级，最低为1，0为错误--------------例如gps频点为：C优先级14 ；P优先级13；Y优先级12；W优先级11

static char codepris[7][MAXFREQ][16]={ /* code priority for each freq-index */

/* L1/E1/B1 L2/E5b/B2 L5/E5a/L3 E6/LEX E5(a+b) */

{"CPYWMNSL","CPYWMNDLSX","IQX" ,"" ,"" ,""}, /* GPS */

{"CPABX" ,"CPABX" ,"IQX" ,"" ,"" ,""}, /* GLO */

{"CABXZ" ,"IQX" ,"IQX" ,"ABCXZ" ,"IQX" ,""}, /* GAL */

{"CLSXZ" ,"LSX" ,"IQXDPZ" ,"LSXEZ" ,"" ,""}, /* QZS */

{"C" ,"IQX" ,"" ,"" ,"" ,""}, /* SBS */

{"IQXDPAN" ,"IQXDPZ" ,"DPX" ,"IQXA" ,"DPX" ,""}, /* BDS */

{"ABCX" ,"ABCX" ,"" ,"" ,"" ,""} /* IRN */

};

系统频点代码段L1/L2/L3/L4，例子作为北斗频点的信息读取，主要通过观测类型的数字进行判断频点信息，例如C1X中的1

extern int code2idx(int sys, uint8_t code)

{

double freq;

switch (sys) {

case SYS_GPS: return code2freq_GPS(code,&freq);

case SYS_GLO: return code2freq_GLO(code,0,&freq);

case SYS_GAL: return code2freq_GAL(code,&freq);

case SYS_QZS: return code2freq_QZS(code,&freq);

case SYS_SBS: return code2freq_SBS(code,&freq);

case SYS_CMP: return code2freq_BDS(code,&freq);

case SYS_IRN: return code2freq_IRN(code,&freq);

}

return -1;

}

switch (obs[0]) {

case '1': *freq=FREQL1; return 0; /* B1C */

case '2': *freq=FREQ1_CMP; return 0; /* B1I */

case '7': *freq=FREQ2_CMP; return 1; /* B2I/B2b */

case '5': *freq=FREQL5; return 2; /* B2a */

case '6': *freq=FREQ3_CMP; return 3; /* B3 */

case '8': *freq=FREQE5ab; return 4; /* B2ab */

}

优先级排序，只对NFREQ个频点排序，选最高优先级，标志pos位作为选择，pos是信号标志位，-1表示该频点观测量不选择，有数据的话表示频点，即L1、L2等。

for (i=0;i<NFREQ;i++) {

for (j=0,k=-1;j<n;j++) {

if (ind->idx[j]==i&&ind->pri[j]&&(k<0||ind->pri[j]>ind->pri[k])) {

k=j;

}

if (k<0) continue;

for (j=0;j<n;j++) {

if (ind->code[j]==ind->code[k]) ind->pos[j]=i;

}

2.代码段

代码段以历元为单位，对于rinex3以上，先读卫星数目decode_obsepoch，然后读取历元内的数据，

typedef struct { /* observation data record */
gtime_t time; /* receiver sampling time (GPST) */
uint8_t sat,rcv; /* satellite/receiver number */
uint16_t SNR[NFREQ+NEXOBS]; /* signal strength (0.001 dBHz) */
uint8_t LLI[NFREQ+NEXOBS]; /* loss of lock indicator */
uint8_t code[NFREQ+NEXOBS]; /* code indicator (CODE_???) */
double L[NFREQ+NEXOBS]; /* observation data carrier-phase (cycle) */
double P[NFREQ+NEXOBS]; /* observation data pseudorange (m) */
float D[NFREQ+NEXOBS]; /* observation data doppler frequency (Hz) */

int timevalid; /* time is valid (Valid GNSS fix) for time mark */
gtime_t eventime; /* time of event (GPST) */
uint8_t qualL[NFREQ+NEXOBS]; /* quality of carrier phase measurement */
uint8_t qualP[NFREQ+NEXOBS]; /* quality of pseudorange measurement */
uint8_t freq; /* GLONASS frequency channel (0-13) */

} obsd_t;

注意：（1）有一块关于rinex2.11及以下的版本需要选择优先级。

（2）在数据分配位置时rinex2.11以上的以pos作为标志位，实际上也已经对优先级选择完成了。写入时pos标志位为-1时已经舍弃

分配方式：

for (i=n=m=q=0;i<ind->n;i++) {

p[i]=(ver<=2.11)?ind->idx[i]:ind->pos[i];

if (ind->type[i]==0&&p[i]==0) k[n++]=i; /* C1? index */

if (ind->type[i]==0&&p[i]==1) l[m++]=i; /* C2? index */

if (ind->type[i]==0&&p[i]==2) r[q++]=i; /* C3? index */

}

导航文件

这部分读取略，主要是对于文件的逐个读取