Function iterative_adjustment

src/transformations/xyzgridshift.cpp:123–151

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static PJ_COORD iterative_adjustment(PJ *P, xyzgridshiftData *Q,
                                     const PJ_COORD &pointInit, double factor) {
    PJ_COORD point = pointInit;
    for (int i = 0; i < 10; i++) {
        PJ_COORD geodetic;
        geodetic.lpz = pj_inv3d(point.xyz, Q->cart);

        double dx, dy, dz;
        if (!get_grid_values(P, Q, geodetic.lp, dx, dy, dz)) {
            return proj_coord_error();
        }

        dx *= factor;
        dy *= factor;
        dz *= factor;

        const double err = SQUARE((point.xyz.x - pointInit.xyz.x) - dx) +
                           SQUARE((point.xyz.y - pointInit.xyz.y) - dy) +
                           SQUARE((point.xyz.z - pointInit.xyz.z) - dz);

        point.xyz.x = pointInit.xyz.x + dx;
        point.xyz.y = pointInit.xyz.y + dy;
        point.xyz.z = pointInit.xyz.z + dz;
        if (err < 1e-10) {
            break;
        }
    }
    return point;
}

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