int main ()
{
    /* The file descriptor. */
    int fd;
    /* Information about the file. */
    struct stat s;
    int status;
    size_t size;
    /* The file name to open. */
    const char * file_name = "file.dem";
    /* The memory-mapped thing itself. */
    const char * mapped;
    int i;

    /* Open the file for reading. */
    fd = open ("file.dem", O_RDONLY);
    check (fd < 0, "open %s failed: %s", file_name, strerror (errno));

    /* Get the size of the file. */
    status = fstat (fd, & s);
    check (status < 0, "stat %s failed: %s", file_name, strerror (errno));
    size = s.st_size;

    /* Memory-map the file. */
    mapped = mmap (0, size, PROT_READ, MAP_PRIVATE, fd, 0);
    check (mapped == MAP_FAILED, "mmap %s failed: %s",
           file_name, strerror (errno));

    /* Now do something with the information. */
    for (i = 0; i < size; i++) {
        // print longitude, latitude, elevation values
    }
    printf("Total iteration : %d", i);

    return 0;
}