gps正用解算卫星个数或GSA语句上传问题
转载时请注明出处和作者文章出处：http://blog.csdn.net/lbmygf/archive/2011/06/28/6573036.aspx
作者：曼云-->孤峰
最近发现很多人都不知道，gps正用解算卫星个数或GSA语句数据上传给谁 ？
在GPGSA的数据中有：
a.GPS DOP and Active Satellites（GSA）当前卫星信息
$GPGSA,<1>,<2>,<3>,<3>,<3>,<3>,<3>,<3>,<3>,<3>,<3>,<3>,<3>,<3>,<4>,<5>,<6>*hh<CR><LF>
<1> 模式，M=手动，A=自动
<2> 定位类型，1=没有定位，2=2D定位，3=3D定位
<3> PRN码（伪随机噪声码），正在用于解算位置的卫星号（01~32，前面的0也将被传输）。
<4> PDOP位置精度因子（0.5~99.9）
<5> HDOP水平精度因子（0.5~99.9）
<6> VDOP垂直精度因子（0.5~99.9）
注意 3 部分，那就是 正在用于解算位置的卫星号 刚好32个标号， 现在看下gps.h中
GpsSvStatus结构体：
typedef struct {
/** set to sizeof(GpsSvInfo) */
size_t size;
/** Pseudo-random number for the SV. */
int prn;
/** Signal to noise ratio. */
float snr;
/** Elevation of SV in degrees. */
float elevation;
/** Azimuth of SV in degrees. */
float azimuth;
} GpsSvInfo;
/** Represents SV status. */
typedef struct {
/** set to sizeof(GpsSvStatus) */
size_t size;
/** Number of SVs currently visible. */
int num_svs;
/** Contains an array of SV information. */
GpsSvInfo sv_list[GPS_MAX_SVS];
/** Represents a bit mask indicating which SVs
* have ephemeris data.
*/
uint32_t ephemeris_mask;
/** Represents a bit mask indicating which SVs
* have almanac data.
*/
uint32_t almanac_mask;
/**
* Represents a bit mask indicating which SVs
* were used for computing the most recent position fix.
*/
uint32_t used_in_fix_mask;
} GpsSvStatus;
注意最后一项 uint32_t used_in_fix_mask ，32位的数据 ，刚好与卫星号（01-32）匹配，所以问题就解决了。
下面吧我代码贴出来给大家参考下：
else if ( !memcmp(tok.p, "GSA", 3) ) {
Token tok_use_prn1 = nmea_tokenizer_get(tzer, 3);
Token tok_use_prn2 = nmea_tokenizer_get(tzer, 4);
Token tok_use_prn3 = nmea_tokenizer_get(tzer, 5);
Token tok_use_prn4 = nmea_tokenizer_get(tzer, 6);
Token tok_use_prn5 = nmea_tokenizer_get(tzer, 7);
Token tok_use_prn6 = nmea_tokenizer_get(tzer, 8);
Token tok_use_prn7 = nmea_tokenizer_get(tzer, 9);
Token tok_use_prn8 = nmea_tokenizer_get(tzer, 10);
Token tok_use_prn9 = nmea_tokenizer_get(tzer, 11);
Token tok_use_prn10 = nmea_tokenizer_get(tzer, 12);
Token tok_use_prn11 = nmea_tokenizer_get(tzer, 13);
Token tok_use_prn12 = nmea_tokenizer_get(tzer, 14);
nmea_reader_update_use_prn(r, tok_use_prn1, tok_use_prn2, tok_use_prn3,
tok_use_prn4, tok_use_prn5, tok_use_prn6,
tok_use_prn7, tok_use_prn8, tok_use_prn9,
tok_use_prn10, tok_use_prn11, tok_use_prn12);
}
static int
nmea_reader_update_use_prn(NmeaReader* r,
Token tok_use_prn1, Token tok_use_prn2, Token tok_use_prn3,
Token tok_use_prn4, Token tok_use_prn5, Token tok_use_prn6,
Token tok_use_prn7, Token tok_use_prn8, Token tok_use_prn9,
Token tok_use_prn10, Token tok_use_prn11, Token tok_use_prn12)
{
if (tok_use_prn1.p +2 == tok_use_prn1.end) r->sv.used_in_fix_mask |= (1 <<( str2int(tok_use_prn1.p, tok_use_prn1.p+2) -1));
if (tok_use_prn2.p +2 == tok_use_prn2.end) r->sv.used_in_fix_mask |= (1 <<( str2int(tok_use_prn2.p, tok_use_prn2.p+2) -1));
if (tok_use_prn3.p +2 == tok_use_prn3.end) r->sv.used_in_fix_mask |= (1 <<( str2int(tok_use_prn3.p, tok_use_prn3.p+2) -1));
if (tok_use_prn4.p +2 == tok_use_prn4.end) r->sv.used_in_fix_mask |= (1 <<( str2int(tok_use_prn4.p, tok_use_prn4.p+2) -1));
if (tok_use_prn5.p +2 == tok_use_prn5.end) r->sv.used_in_fix_mask |= (1 <<( str2int(tok_use_prn5.p, tok_use_prn5.p+2) -1));
if (tok_use_prn6.p +2 == tok_use_prn6.end) r->sv.used_in_fix_mask |= (1 <<( str2int(tok_use_prn6.p, tok_use_prn6.p+2) -1));
if (tok_use_prn7.p +2 == tok_use_prn7.end) r->sv.used_in_fix_mask |= (1 <<( str2int(tok_use_prn7.p, tok_use_prn7.p+2) -1));
if (tok_use_prn8.p +2 == tok_use_prn8.end) r->sv.used_in_fix_mask |= (1 <<( str2int(tok_use_prn8.p, tok_use_prn8.p+2) -1));
if (tok_use_prn9.p +2 == tok_use_prn9.end) r->sv.used_in_fix_mask |= (1 <<( str2int(tok_use_prn9.p, tok_use_prn9.p+2) -1));
if (tok_use_prn10.p +2 == tok_use_prn10.end) r->sv.used_in_fix_mask |= (1 <<( str2int(tok_use_prn10.p, tok_use_prn10.p+2) -1));
if (tok_use_prn11.p +2 == tok_use_prn11.end) r->sv.used_in_fix_mask |= (1 <<( str2int(tok_use_prn11.p, tok_use_prn11.p+2) -1));
if (tok_use_prn12.p +2 == tok_use_prn12.end) r->sv.used_in_fix_mask |= (1 <<( str2int(tok_use_prn12.p, tok_use_prn12.p+2) -1));
return 0;
}
so 完工了