GPS距离计算错误

Question

我正在使用l80 GPS模块，使用GPS坐标计算距离。当我检查办公室的总距离时，有时会正确显示＆＃34; 0＆＃34;但有时它显示＆＃34; 9223372036854775808.775808＆＃34;有时它显示＆＃34; 2.18654＆＃34;。

这是我使用的代码：

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 * 60 * 1.609344;
  dist+=dist;
  return (dist);
}

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

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

以下是我的输出示例：

old_lat:13.006952    old_lon:80.257065   new_lat:13.006952    new_lon:80.257065 Total distance: 0.000000

old_lat:13.006949    old_lon:80.257065   new_lat:13.006948   new_lon:80.257065Total distance: 9223372036854775808.775808