int gps_parse_line(struct gps_t *gps, char *buffer, int size)
{
    float lon, lat;
    char gps_status;   
    char n=0,m=0,f=0;  
    if((buffer[1] == 'G')   
        &&(buffer[2] == 'P')   
        &&(buffer[3] == 'R')   
        &&(buffer[4] == 'M')   
        &&(buffer[5] == 'C'))//GPRMC   
    {   
        for(n=0;n<100;n++)   
        {      
            if(buffer[n] == ',')   
            {   
                m ++;

                if(m == 2)
                {   
                    gps_status = buffer[n+1];                  
                }   
                if(m == 3)
                {   
                    if(gps_status == 'A')   
                    {   
                        lat =((float)(buffer[n+1])
                            +(float)(buffer[n+2])   
                            +(float)(buffer[n+3])
                            +(float)(buffer[n+4])
                            +(float)(buffer[n+6])
                            +(float)(buffer[n+7])
                            +(float)(buffer[n+8])
                            +(float)(buffer[n+9]));
                                                   
                    }   
                }   
                if(m == 4)   
                {   
                    "N";   
                }   
                if(m == 5)
                {   
                    
                    lon =((float)(buffer[n+1])  
                        +(float)(buffer[n+2])   
                        +(float)(buffer[n+3])  
                        +(float)(buffer[n+4])
                        +(float)(buffer[n+5])
                        +(float)(buffer[n+7])
                        +(float)(buffer[n+8])
                        +(float)(buffer[n+9])
                        +(float)(buffer[n+10]));
                    
                      }   
                if(m == 6)   
                {   
                    "E";   
                }   
            }   
        }   

    }   
    gps->lat=lat;
    gps->lon=lon;
   
    return 0;
}

int gps_get(struct gps_t *gps, float *lon, float *lat)
{
   
    *lon=gps->lon;
    *lat=gps->lat;
    return 0;
}



main:

int main(int argc, char *argv[])
{

    float lon, lat;
    struct gps_t gps;
    char *buffer = "$GPRMC,013946.00,A,3202.1855,N,11849.0769,E,0.05,218.30,111105,4.5,W,A*20";
   
    gps_parse_line(&gps, buffer, strlen(buffer));
    gps_get(&gps, &lon, &lat);
    printf("lon: %f, lat: %f\n", lon, lat);
    getchar();
｝

为什么：      纬度：lat 开始值3202.1855     到 gps->lat=lat;  
              经度：lon开始值 11849.0769    到 gps->lon=lon;
lat值变为410.000000;
lon值变为477.000000;
debug时  gps->lat显示         ： gps->lat    -1.0737418e+008    float



[ 本帖最后由 Rick_gu 于 2014-5-29 15:40 编辑 ]

连 struct gps_t 都没有将定义贴出来，你就不能贴出别人能直接编译调试的代码吗？

#include <stdio.h>
#include <string.h>

struct gps_t
{
    double lon;
    double lat;
};

int gps_parse_line( struct gps_t *gps, const char *buffer )
{
    if( 2 != sscanf(buffer,"$GPRMC,%*f,A,%lf,N,%lf",&gps->lat,&gps->lon) )
        return 1; // 失败
    return 0; // 成功
}

int main(int argc, char *argv[])
{
    struct gps_t gps;
    const char *buffer = "$GPRMC,013946.00,A,3202.1855,N,11849.0769,E,0.05,218.30,111105,4.5,W,A*20";
    if( 0 == gps_parse_line(&gps,buffer) )
        printf( "lon: %.4f, lat: %.4f\n", gps.lon, gps.lat );

    return 0;
}

输出：
lon: 11849.0769, lat: 3202.1855

将 #include <string.h> 那一句删除掉，多余的

很明显把字符串转成浮点数那个的发那个有问题
                    lon =((float)(buffer[n+1])  
                        +(float)(buffer[n+2])   
                        +(float)(buffer[n+3])  
                        +(float)(buffer[n+4])
                        +(float)(buffer[n+5])
                        +(float)(buffer[n+7])
                        +(float)(buffer[n+8])
                        +(float)(buffer[n+9])
                        +(float)(buffer[n+10]))
这只是简单的把ASCII码相加。