程序有关介绍请参考图书3.6.1节内容

程序运行结果如下图：

#include <iostream>
#include <fstream>
#include<vector>
#include <GL/glut.h>
using namespace std;

class MapPoint
{
public:
    double longitude;
    double latitude;
};
class Polygon
{
public:
    vector<MapPoint> points; //多边形的顶点序列
};
vector<Polygon*> polys; //多边形集合
vector<Polygon*> ReadMapData(char* filename)
{
    int PointCount;
    vector<Polygon*> polygons;
    ifstream fs(filename);
    while(fs.eof()!=true)
    {
        Polygon* poly=new Polygon;
        fs>>PointCount;
        cout<<PointCount<<endl;
        for(int i=0;i<PointCount;i++)
        {
            MapPoint p;
            fs>>p.longitude>>p.latitude;
            poly->points.push_back(p);
        }
        polygons.push_back(poly);

    }
    return polygons;
}
void display(void)
{   
    glClear (GL_COLOR_BUFFER_BIT);   
    //用蓝色色绘制各省边界
    glColor3f (0.0, 0.0, 1.0);
    glPolygonMode(GL_BACK, GL_LINE);    
    for(int i=0;i<polys.size();i++)
    {       
        vector<MapPoint> points=polys[i]->points;
        glBegin(GL_LINE_STRIP);
        for(int j=0;j<points.size();j++)
        {           
            glVertex3f (points[j].longitude, points[j].latitude, 0.0);       
        }
        glEnd();
    }   
    glFlush();
}
void init (void)
{
    //设置背景颜色
    glClearColor (1.0, 1.0, 1.0, 0.0);
    //初始化观察值
    glMatrixMode(GL_PROJECTION);    //将矩阵模式设为投影
    glLoadIdentity();                 //对矩阵进行单位化
    glOrtho(110.0, 118.0, 30.0, 38.0, -1.0, 1.0);   //构造平行投影矩阵
}
int main(int argc, char** argv)
{
    //数据文件请到http://files.cnblogs.com/opengl/HenanCounty.rar下载放到D盘根目录下并解压
    char* filename="D:/HenanCounty.txt";

    polys=ReadMapData(filename);   
    glutInit(&argc, argv);
    glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);  //单缓存和RGB
    glutInitWindowSize (500, 500);
    glutInitWindowPosition (100, 100);
    glutCreateWindow ("地图绘制");
    init ();
    glutDisplayFunc(display);     //显示回调函数
    glutMainLoop();
    return 0;
}