grass gis 的求buffer最基本内容

来源：互联网发布：qq三国张飞打技能数据编辑：程序博客网时间：2024/05/16 09:55

重叠部分的计算我没看懂

核心部分是:

基于椭球切线原理求平行线

使用求椭球切点函数elliptic_tangent计算切点向量,

以切点向量计算平行线

// 向量标准化函数/* norm_vector() calculates normalized vector form two points */void NormalizeVector(double y0, double x0, double y1, double x1, double *x, double *y){    double dx, dy, len;    dy = y1 - y0;    dx = x1 - x0;    if ((dx == 0) && (dy == 0))     {*x = 0;*y = 0;return;    }    len = LENGTH(dx, dy);    *x = dx / len;    *y = dy / len;    return;}void Test_NormalizeVector0(double x1, double y1, double x2, double y2){double x, y;NormalizeVector(y1,x1,y2,x2, &x, &y);LogStr("Normalize %f,%f, %f,%f to %f, %f", x1, y1, x2, y2, x, y);}void Test_NormalizeVector(){Test_NormalizeVector0(0,0,1,0);Test_NormalizeVector0(0,0,2,0);Test_NormalizeVector0(0,0,1,1);Test_NormalizeVector0(0,0,2,2);Test_NormalizeVector0(0,0,0,2);Test_NormalizeVector0(0,0,0,-2);Test_NormalizeVector0(0,0,-3,-2);Test_NormalizeVector0(0,0,-3,2);Test_NormalizeVector0(1,1,1,0);Test_NormalizeVector0(1,1,2,0);Test_NormalizeVector0(1,1,1,1);Test_NormalizeVector0(1,1,2,2);Test_NormalizeVector0(1,1,0,2);Test_NormalizeVector0(1,1,0,-2);Test_NormalizeVector0(1,1,-3,-2);Test_NormalizeVector0(1,1,-3,2);}// 求切点向量void EllipticTangent(double x, double y, double *px, double *py){    double u =0, v=0, len;double da = GPS_MeteringData.daFactor;double da2 = da*da;double db = GPS_MeteringData.dbFactor;double db2 = db*db;if(da != 0 || db != 0){u = da2 * y;v = -db2 * x;len = 1/sqrt(db2*x*x+da2*y*y);u *= len;v *= len;*px = u;*py = v;}*px = u;*py = v;}void Test_EllipticTangent0(double x, double y){double tx, ty;EllipticTangent(x, y, &tx, &ty);LogStr("Test_EllipticTangent0 %f,%f to %f, %f", x, y, tx, ty);}void Test_EllipticTangent(){Test_EllipticTangent0(1,0);Test_EllipticTangent0(2,0);Test_EllipticTangent0(1,1);Test_EllipticTangent0(2,2);Test_EllipticTangent0(0,2);Test_EllipticTangent0(0,-2);Test_EllipticTangent0(-3,-2);Test_EllipticTangent0(-3,2);}

0 0