手机gps信息提取并储存到本地_文件读写以及NMEA码中GPS信息的提取

首先先了解下什么是NMEA码，这里有很好的解释，就不直接搬运了

首先要找到包含GPS信息的文本行，即字符串GPGGA所在行

$GPGGA,052551.00,3409.341502,N,10853.663318,E,1,05,1.2,459.4,M,-28.0,M,,*4E

在实际的工程应用中，可能由于各种原因(比如设备在室内时就无法获取GPS信息)，GPS信息并不是实时都可以获取准确的完整的值，因此在GPS.log文件内，会存在一些不完整的GPS信息。

$GPGGA,,,,,,0,,,,,,,,*66　　//这是我在室内定位的GPS信息

所以要确定一个文本行确实存在完整的GPS信息，必须确认GPGGA, N/S, W/E 三个字符串均存在。然后再定位纬度所在位置，提取数值即可。

实现代码如下

#include

#include

#include

#include

#include

#include

#include

#include

#include

#define FILE_PATH "/home/mr_han/code/exp/GPS.log"

#define READ_MAX 150

#define GPS_DATA 15

#define GPS_KEY "GPGGA"

#define bool char

#define true 1

#define false 0

void gps_cal(double p, char q, int *angle, float *min)//将原始GPS信息转换为度分形式

{

*angle = p/100;

*min = (p-*angle*100)/60;

}

int Search_comma(char *p, int L)//由GPGGA纬度字段前的逗号即可找到得到纬度GPS信息

{

while(p[L-1]!=',')

{

--L;

}

return L;

}

/*从文件中c查找完整GPS信息，参数依次为， 文件路径(名)，纬度值，经度值， 经度，纬度*/

bool get_gps_data(const char *file_name, double *p, double *q, char *longitude, char *latitude)

{

char *rw = NULL;

int location = 0, i = 0, N=0,S=0,E=0,W=0;

char read_line_buff[READ_MAX], gps[GPS_DATA];

memset(gps, 0, GPS_DATA);

FILE *fd = fopen(FILE_PATH, "r");

if(fd == NULL)

{

printf("Open file error!n");

return false;

}

while(!feof(fd))

{

memset(read_line_buff, 0, READ_MAX);

rw = fgets(read_line_buff, READ_MAX, fd);//每次从文件读取一行，

if(rw == NULL)

return false;

if(strstr(read_line_buff, GPS_KEY)!=NULL)

{

N = (strchr(read_line_buff,'N')==NULL ? 0 : 1);

S = (strchr(read_line_buff, 'S')==NULL ? 0 : 2);

E = (strchr(read_line_buff, 'E')==NULL ? 0 : 4);

W = (strchr(read_line_buff, 'W')==NULL ? 0 : 7);/

i = N+S+E+W;

/*完整的GPS,信息只可能存在 NE东经北纬、NW西经北纬、SE东经南纬、SW西经南纬，分别给四种组合不同的权值，用以确定是那种情况*/

switch(i)//这里case可以调用函数用来代替goto语句

{

case 5:

*longitude = 'E';

*latitude = 'N';

i = 0;

fclose(fd);

goto NE;

case 6:

*longitude = 'E';

*latitude = 'S';

i = 0;

fclose(fd);

goto SE;

case 8:

*longitude = 'W';

*latitude = 'N';

i = 0;

fclose(fd);

goto NW;

case 9:

*longitude = 'W';

*latitude = 'S';

i = 0;

fclose(fd);

goto SW;

default: continue;

}

}

}

NE:

rw = strchr(read_line_buff, 'N');//strchr函数会在第一个参数字符串内找第二个参数字符，找到返回一个地址，找不到返回空

location = rw - read_line_buff - 1;//地址相减，得到数字，这一步主要是定位到纬度前的逗号，$GPGGA,052551.00,3409.341502,N location即N前的逗号

location = Search_comma(read_line_buff,location);//再向前定位上一个逗号即可找到GPS信息

while(read_line_buff[location+1] != 'N')

gps[i++] = read_line_buff[location++];

*p = atof(gps);

memset(gps, 0, GPS_DATA);

i = 0;

location = location+3;//3409.341502,N,10853.663318,E,纬度赋值完成后，location在N前逗号出，只需向后跳三位即可找到经度信息

while(read_line_buff[location+1] != 'E')

gps[i++] = read_line_buff[location++];

*q = atof(gps);

return true;

SE:

rw = strchr(read_line_buff, 'S');

location = rw - read_line_buff - 1;

location = Search_comma(read_line_buff, location);

while(read_line_buff[location+1] != 'S')

gps[i++] = read_line_buff[location++];

*p = atof(gps);

memset(gps, 0, GPS_DATA);

i = 0;

location = location + 3;

while(read_line_buff[location+1] != 'E')

gps[i++] = read_line_buff[location++];

*q = atof(gps);

return true;

NW:

rw = strchr(read_line_buff, 'N');

location = rw - read_line_buff - 1;

location = Search_comma(read_line_buff, location);

while(read_line_buff[location+1] != 'N')

gps[i++] = read_line_buff[location++];

*p = atof(gps);

memset(gps, 0, GPS_DATA);

i = 0;

location =location + 3;

while(read_line_buff[location+1] != 'W')

gps[i++] = read_line_buff[location++];

*q = atof(gps);

return true;

SW:

rw = strchr(read_line_buff, 'S');

location = rw - read_line_buff - 1;

location = Search_comma(read_line_buff, location);

while(read_line_buff[location+1] != 'S')

gps[i++] = read_line_buff[location++];

*p = atof(gps);//atof函数可将字符串转为double后返回，转换失败返回0

memset(gps, 0, GPS_DATA);

i = 0;

location =location + 3;

while(read_line_buff[location+1] != 'W')

gps[i++] = read_line_buff[location++];

*q = atof(gps);

return true;

}

char *print(char p)

{

switch(p)

{

case 'S':return "南纬";

case 's':return "南纬";

case 'N':return "北纬";

case 'n':return "北纬";

case 'W':return "东经";

case 'w':return "东经";

case 'E':return "西经";

case 'e':return "西经";

default: return "经纬错误";

}

}

int main()

{

int angle=0;

float min=0;

char longitude=0, latitude=0;

double gps_g=0, gps_i=0;//gps_g经度 gps_i纬度

get_gps_data(FILE_PATH, &gps_i, &gps_g, &longitude, &latitude);

printf("gps: %lf %c, %lf %cn",gps_i, latitude, gps_g, longitude);

/*gps_cal(gps_g, longitude, &angle, &min);

printf("%s %d度%f分", print(longitude), angle, min);

gps_cal(gps_i, latitude, &angle, &min);

printf("%s %d度%f分n", print(latitude), angle, min);*/

gps_cal(gps_i, latitude, &angle, &min);

printf("%s %d度%f分", print(latitude), angle, min);

gps_cal(gps_g, longitude, &angle, &min);

printf("%s %d度%f分n", print(longitude), angle, min);

return 0;

}

效果如下

附测试用的GPS.log文件部分信息

$GPVTG,,T,,M,,N,,K,N*2C

$GPGSA,A,1,,,,,,,,,,,,,,,*1E

$GPGGA,,,,,,0,,,,,,,,*66

$GPRMC,,V,,,,,,,,,,N*53

$GPGSV,3,1,10,10,49,322,50,12,15,119,40,20,78,352,49,25,09,151,39*7F

$GPGSV,3,2,10,32,28,272,48,14,13,260,,15,25,063,,21,41,203,*7B

$GPGSV,3,3,10,24,51,053,,27,,,*49

$GPVTG,,T,,M,,N,,K,N*2C

$GPGSA,A,1,,,,,,,,,,,,,,,*1E

$GPGGA,,,,,,0,,,,,,,,*66

$GPRMC,,V,,,,,,,,,,N*53

$GPGSV,3,1,11,10,49,322,51,12,15,119,40,20,78,352,49,25,09,151,38*7E

$GPGSV,3,2,11,32,28,272,47,14,13,260,,15,25,063,,21,41,203,*75

$GPGSV,3,3,11,24,51,053,,27,,,,40,,,36*49

$GPGGA,052550.00,3409.338831,N,10853.658643,E,1,04,1.4,467.2,M,-28.0,M,,*43

$GPVTG,1.5,T,4.6,M,0.3,N,0.6,K,A*20

$GPRMC,052550.00,A,3409.338831,N,10853.658643,E,0.3,1.5,121218,3.1,W,A*25

$GPGSA,A,2,10,12,20,32,,,,,,,,,1.6,1.4,0.9*39

$GPGSV,3,1,11,10,49,322,51,12,15,119,40,14,13,260,29,15,25,063,30*77

$GPGSV,3,2,11,20,78,352,49,21,41,203,22,24,51,053,33,25,09,151,39*7E

$GPGSV,3,3,11,32,28,272,47,27,,,,40,,,38*4C

$GPGGA,052551.00,3409.341502,N,10853.663318,E,1,05,1.2,459.4,M,-28.0,M,,*4E

$GPVTG,1.5,T,4.6,M,0.0,N,0.0,K,A*25

$GPRMC,052551.00,A,3409.341502,N,10853.663318,E,0.0,1.5,121218,3.1,W,A*27

$GPGSA,A,2,10,12,20,24,32,,,,,,,,1.4,1.2,0.8*3A

$GPGSV,3,1,11,10,49,322,51,12,15,119,40,14,13,260,30,15,25,063,30*7F

$GPGSV,3,2,11,20,78,352,49,21,41,203,22,24,51,053,33,25,09,151,39*7E

$GPGSV,3,3,11,32,28,272,47,27,,,,40,,,38*4C

$GPGGA,052552.00,3409.340891,N,10853.662052,E,1,05,1.2,462.9,M,-28.0,M,,*42

$GPVTG,1.5,T,4.6,M,0.0,N,0.0,K,A*25

$GPRMC,052552.00,A,3409.340891,N,10853.662052,E,0.0,1.5,121218,3.1,W,A*2E

$GPGSA,A,2,10,12,20,24,32,,,,,,,,1.4,1.2,0.8*3A

$GPGSV,3,1,11,10,49,322,51,12,15,119,40,14,13,260,30,15,25,063,27*79

$GPGSV,3,2,11,20,78,352,49,21,41,203,20,24,51,053,31,25,09,151,39*7E

$GPGSV,3,3,11,32,28,272,47,27,,,,40,,,38*4C

$GPGGA,052553.00,3409.340173,N,10853.661041,E,1,05,1.2,465.3,M,-28.0,M,,*4A

$GPVTG,1.5,T,4.6,M,0.0,N,0.0,K,A*25

$GPRMC,052553.00,A,3409.340173,N,10853.661041,E,0.0,1.5,121218,3.1,W,A*2B

$GPGSA,A,2,10,12,20,24,32,,,,,,,,1.4,1.2,0.8*3A

$GPGSV,3,1,11,10,49,322,50,12,15,119,41,14,13,260,30,15,25,063,27*79

$GPGSV,3,2,11,20,78,352,49,21,41,203,20,24,51,053,32,25,09,151,39*7D

$GPGSV,3,3,11,32,28,272,46,27,,,,40,,,39*4C

$GPGGA,052554.00,3409.339925,N,10853.660214,E,1,05,1.2,466.6,M,-28.0,M,,*4D

$GPVTG,1.5,T,4.6,M,0.0,N,0.0,K,A*25

$GPRMC,052554.00,A,3409.339925,N,10853.660214,E,0.0,1.5,121218,3.1,W,A*2A

$GPGSA,A,2,10,12,20,24,32,,,,,,,,1.4,1.2,0.8*3A

$GPGSV,3,1,11,10,49,322,51,12,15,119,40,14,13,260,31,15,25,063,28*77

$GPGSV,3,2,11,20,78,352,49,21,41,203,21,24,51,053,32,25,09,151,39*7C

$GPGSV,3,3,11,32,28,272,46,27,,,,40,,,39*4C

$GPGGA,052555.00,3409.340026,N,10853.659458,E,1,05,1.2,466.2,M,-28.0,M,,*48

$GPVTG,1.5,T,4.6,M,0.0,N,0.0,K,A*25

$GPRMC,052555.00,A,3409.340026,N,10853.659458,E,0.0,1.5,121218,3.1,W,A*2B

$GPGSA,A,2,10,12,20,24,32,,,,,,,,1.4,1.2,0.8*3A

$GPGSV,3,1,11,10,49,322,51,12,15,119,40,14,13,260,30,15,25,063,28*76

$GPGSV,3,2,11,20,78,352,49,21,41,203,22,24,51,053,32,25,09,151,39*7F

$GPGSV,3,3,11,32,28,272,46,27,,,,40,,,39*4C

$GPGGA,052556.00,3409.339490,N,10853.658951,E,1,05,1.2,465.8,M,-28.0,M,,*40

$GPVTG,1.5,T,4.6,M,0.0,N,0.0,K,A*25