Question

我正在计算PIC单片机中GPS使用纬度和经度的车辆总行驶距离。这里我的GPS模块处于空闲状态（不移动），因此总距离应该显示为“0”（零），是的它显示为零。但有时它显示奇怪的值“9223372036854775808.775808”，后来我的总距离变为零。

这是我的代码;

    #include<stdio.h>
#include<math.h>
#include <string.h>
#define COMMA 0x2C
#define MAXSIZE 100
#define pi 3.14159265358979323846
double deg2rad(double);
double rad2deg(double);
float stof(char* s);
float Nmea_Degree(char *data);
double dist;
double distance(double lat1, double lon1, double lat2, double lon2, char unit);
float old_lat=0;
float old_lon=0;
float new_lat=0;
float new_lon=0;
int flag=0;
double theta, dist=0,old_dist=0;
int main()
{

    /* Get lattitude */
    int k=0,j=0;
    unsigned  char lastCommaPosition;
    unsigned char stringRead[MAXSIZE]="$GPRMC,124130.000,A,1300.4147,N,08015.4269,E,0.13,224.13,151015,,,D*6A";
    //$GPRMC,124130.000,A,1300.4147,N,08015.4269,E,0.13,224.13,151015,,,D*6A
    //$GPGGA,1300.80,4548.32609,N,01557.99352,E,1,07,1.30,129.1,M,41.4,M,,*5E
    unsigned char *pChar;
    unsigned char latitudeCardinalString[3];
    unsigned char latitudeString[11];
    unsigned char longitudeString[12];
    float longitude;
    float latitude;
    if(strstr(stringRead,"GPRMC")) //if(strstr(nmea,"GPRMC"))
    {
    pChar = stringRead;
    lastCommaPosition = j;
    j = lastCommaPosition + 1;
    while(*(pChar+j) != COMMA)
    {
    latitudeString[k] = *(pChar+j);
    j++;
    k++;
    }
    j=19;
    k=18;
    lastCommaPosition = j; 
    latitudeString[k] = '\0'; 
    sscanf(latitudeString, "%f", &latitude);
    pChar = stringRead;
    j = lastCommaPosition + 1;
    k = 0;
    while(*(pChar+j) != COMMA) {
    latitudeCardinalString[k] = *(pChar+j);
    j++;
    k++;
    }
    lastCommaPosition = j;
    latitudeCardinalString[k] = '\0';
    printf("Latitude(f):%f",Nmea_Degree(latitudeCardinalString)); ////Latitude
    printf("\n");

    new_lat=Nmea_Degree(latitudeCardinalString);
    /* Get Longitude */
    pChar = stringRead;
    j = lastCommaPosition + 1;
    k = 0;
    j=32;
    while(*(pChar+j) != COMMA) {
    longitudeString[k] = *(pChar+j);
    j++;
    k++;
    }

    lastCommaPosition = j;
    longitudeString[k] = '\0';
    sscanf(longitudeString, "%f", &longitude);
    printf("Longitude(f):%f",Nmea_Degree(longitudeString));  ////Longitude
    printf("\n");

    /*extract UTC time*/
        pChar=gpsdata;
        j = 1;  /* start of time field */
        k = 0;
        while(*(pChar+j) != COMMA)
        {
        timeString[k] = *(pChar+j);
        j++;
        k++;
        }
        lastCommaPosition = j;
        timeString[k] = '\0';
        sscanf(timeString, "%ld", &utcTime);
        utcHour = (utcTime/10000);   /* extract Hours from long */
        utcMinutes = (utcTime - (utcHour*10000))/100;  /* extract minutes from long */
        utcSeconds = utcTime - (utcHour*10000) - (utcMinutes*100); /* extract seconds from long */
        if(utcHour >= 4 && utcHour <= 23) estHour = utcHour + 5;
        else estHour = utcHour + 20;
        estMinutes = utcMinutes;
        estSeconds = utcSeconds;

    /*Total distance calculation*/  

    if(utcSeconds==15 || utcSeconds==30 || utcSeconds==45 || utcSeconds==00)
    {

    if(flag==0)
    {
        old_lat=Nmea_Degree(latitudeCardinalString);
        old_lon=Nmea_Degree(longitudeString);
        flag=1;
    }
    else
    {
        new_lat=Nmea_Degree(latitudeCardinalString);
        new_lon=Nmea_Degree(longitudeString);

        printf("%f",distance(old_lat,old_lon,new_lat,new_lon,'N'));
        old_lat=new_lat;
        old_lon=new_lon;
    }


    }
    else
    {

        printf("Bad GPS");
    }
    return 0;
}

float stof(char* s)
{
    int point_seen;
    float rez = 0, fact = 1;
    if (*s == '-')
    {
        s++;
        fact = -1;
    }
    for (point_seen = 0; *s; s++)
    {
        if (*s == '.')
        {
        point_seen = 1;
        continue;
        }
        int d = *s - '0';
        if (d >= 0 && d <= 9)
        {
        if (point_seen) fact /= 10.0f;
        rez = rez * 10.0f + (float)d;
        }
    }
    return rez * fact;
}

float Nmea_Degree(char *data)
{
    double  Value;
    int Degree;
    double  minute;
    Degree=stof(data)/100;
    minute=(float)stof(data)-(100*Degree);
    Value = Degree+(minute/60);
    return Value;
}

double distance(double lat1, double lon1, double lat2, double lon2, char unit) {
  //double theta, dist;
  theta = lon1 - lon2;
  dist = sin(deg2rad(lat1)) * sin(deg2rad(lat2)) + cos(deg2rad(lat1)) * cos(deg2rad(lat2)) * cos(deg2rad(theta));
  dist = acos(dist);
  dist = rad2deg(dist);
  dist = dist * 60 * 1.1515;
  dist+=dist;
 return (dist);
}

double deg2rad(double deg) {
      return (deg * pi / 180);
    }

    double rad2deg(double rad) {
          return (rad * 180 / pi);
    }

这是奇怪的价值：

    Latitude:13.006949
Longitude:80.257065
Latitude:13.006949
Longitude:80.257065
Latitude:13.006949
Longitude:80.257065
interval:    02
old_lat:13.006952    old_lon:80.257065   new_lat:13.006949   new_lon:80.257065Total distance: 0.000000
Latitude:13.006949
Longitude:80.257065
Latitude:13.006949
Longitude:80.257065
Latitude:13.006949
Longitude:80.257065
Latitude:13.006949
Longitude:80.257065
Latitude:13.006949
Longitude:80.257065
Latitude:13.006949
Longitude:80.257065
Latitude:13.006949
Longitude:80.257065
Latitude:13.006949
Longitude:80.257065
Latitude:13.006949
Longitude:80.257065
Latitude:13.006948
Longitude:80.257065
Latitude:13.006948
Longitude:80.257065
Latitude:13.006948
Longitude:80.257065
Latitude:13.006948
Longitude:80.257065
Latitude:13.006948
Longitude:80.257065
Latitude:13.006948
Longitude:80.257065
old_lat:13.006949    old_lon:80.257065   new_lat:13.006948   new_lon:80.257065Total distance: 9223372036854775808.775808

这里我在stringRead变量中传递我的gps uart值。问题是什么？

...谢谢

在计算与GPS的距离时获得奇怪的值 - C.

0 个答案: