Question

如何提高以下内容的准确性（精确度）？

struct Degree_Minutes { signed int degrees; signed int minutes; double seconds; };
Degree_Minutes geo_dec_to_deg (double dec)
{
    Degree_Minutes degrees_minutes;
    signed int degrees, minutes;
    double remainder, temp, seconds;

    remainder = fmod(dec, 1);
    degrees_minutes.degrees = dec - remainder;
    temp = remainder*60;
    remainder = fmod(temp,1);
    degrees_minutes.minutes = temp-remainder;
    degrees_minutes.seconds = remainder*60;

    return degrees_minutes;
}

    double geo_deg_to_dec (Degree_Minutes degrees)
{
    double decimal = degrees.degrees + (degrees.minutes/60) + (degrees.seconds/60);
    return decimal;
}

int main(int argc, char **argv)
{
    Degree_Minutes deg;
    double decimal = 38.898556;

    deg = geo_dec_to_deg(decimal);
    cout << "Results of geo_dec_to_deg function: \n" << decimal << " was converted to " << deg.degrees << " degrees, " << deg.minutes << " minutes, " << deg.seconds << " seconds.\n";
    decimal = geo_deg_to_dec(deg);
    cout << "Results of geo_dec_to_deg function: \n" << deg.degrees << " degrees, " << deg.minutes << " minutes, " << deg.seconds << " seconds was converted to " << decimal << "\n";

    return EXIT_SUCCESS;
}

编辑：忘了在这里添加一个结构：

struct Degree_Minutes { signed int degrees; signed int minutes; double seconds; };

当您从十进制转换为度/分/秒然后再返回到十进制时，当原始为38.898556时，最终会以38.9134结束。

Answer 1

由于意外的整数除法，您遇到了舍入/截断错误。要获得正确的双精度，您需要将degrees.minutes和degrees.seconds隐式转换为double，如下所示：

double decimal = degrees.degrees + (degrees.minutes/60.0) + (degrees.seconds/3600.0);

请注意60 - ＆gt; 60.0并在秒字段中更正60到3600。

Answer 2

有两个问题。

首先，minutes结构的Degree_Minutes成员被声明为整数类型，因此degrees.minutes/60将整数除以整数，从而产生截断的整数结果。将其更改为degrees.minutes/60.会产生浮点结果。

其次，degrees.seconds/60不正确。这应该是degrees.seconds/3600或degrees.seconds/60应添加到degrees.minutes，然后总和除以60.

Answer 3

#include <stdlib.h>
#include <iostream>
#include <math.h>

using namespace std;

struct Degree_Minutes { signed int degrees; signed int minutes; double seconds; };

Degree_Minutes geo_dec_to_deg (double dec)
{
    Degree_Minutes degrees_minutes;
    signed int degrees, minutes;
    double remainder, temp, seconds;

    remainder = fmod(dec, 1);
    degrees_minutes.degrees = dec - remainder;
    temp = remainder*60.0;
    remainder = fmod(temp,1);
    degrees_minutes.minutes = temp-remainder;
    degrees_minutes.seconds = remainder*60.0;

    return degrees_minutes;
}

double geo_deg_to_dec (Degree_Minutes degrees)
{
    double decimal = degrees.degrees + (degrees.minutes/60.0) + (degrees.seconds/60.0/60.0);
    return decimal;
}

int main(int argc, char **argv)
{
    Degree_Minutes deg;
    double decimal = 38.898556;

    deg = geo_dec_to_deg(decimal);
    cout << "Results of geo_dec_to_deg function: \n" << decimal << " was converted to " << deg.degrees << " degrees, " << deg.minutes << " minutes, " << deg.seconds << " seconds.\n";
    cout << "This should be: 38deg 53' 54.801\"" << endl;
    cout << endl;
    decimal = geo_deg_to_dec(deg);
    cout << "Results of geo_dec_to_deg function: \n" << deg.degrees << " degrees, " << deg.minutes << " minutes, " << deg.seconds << " seconds was converted to " << decimal << "\n";
    cout << "This should be: 38.898556" << endl;

    return EXIT_SUCCESS;
}

你几乎拥有它。您需要通过显式指定小数来强制双重除法（如另一个答案中所示），但您还需要将秒数除以60两次。在实践中，我可能会将其更改为degrees.seconds/3600，但我将其保留为原样来说明。

如何提高代码的精度

3 个答案: