distance between a line segment and a point in a map

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I assume that my robot is an rectangle so want to know the position of each corner point of my rectangle. So as I understand to get the position and orientation I need these two tf transforms. I wont the have the position and orientation of all four corner point of the rectangle . My rectangle have dimension 60x90cm . The center of the base_link frame is the center of the rectangle.After that I create the 4 line segments . So to calculate the distance between the line segment and the point in the map I tried this code. Bit not sure that is ok. This is my node

Any help?

tf::Stamped<tf::Pose> corner1(
            tf::Pose(tf::Quaternion(0, 0, 0, 1), tf::Vector3(0.30, -0.45, 0.0)),
                                ros::Time(0), "base_link");
        tf::Stamped<tf::Pose> corner2(
            tf::Pose(tf::Quaternion(0, 0, 0, 1), tf::Vector3(0.30, 0.45, 0.0)),
                                ros::Time(0), "base_link");
        tf::Stamped<tf::Pose> corner3(
            tf::Pose(tf::Quaternion(0, 0, 0, 1), tf::Vector3(-0.30, -0.45, 0.0)), 
                                ros::Time(0), "base_link");
        tf::Stamped<tf::Pose> corner4(
            tf::Pose(tf::Quaternion(0, 0, 0, 1), tf::Vector3(-0.30, 0.45, 0.0)), 
                                ros::Time(0), "base_link");

    tf::Stamped<tf::Pose> transformed_corner_1;
        transform_listener.transformPose("map", corner1, transformed_corner_1);
    tf::Stamped<tf::Pose> transformed_corner_2;
        transform_listener.transformPose("map", corner2, transformed_corner_2);
    tf::Stamped<tf::Pose> transformed_corner_3;
        transform_listener.transformPose("map", corner3, transformed_corner_3);
    tf::Stamped<tf::Pose> transformed_corner_4;
        transform_listener.transformPose("map", corner4, transformed_corner_4);



    double x_vect_a = transformed_corner_1.getOrigin().x();
    double y_vect_a = transformed_corner_1.getOrigin().y();

    double x_vect_b = transformed_corner_2.getOrigin().x();
    double y_vect_b = transformed_corner_2.getOrigin().y();

    double x_vect_c = transformed_corner_3.getOrigin().x();
    double y_vect_c = transformed_corner_3.getOrigin().y();         

    double x_vect_d = transformed_corner_4.getOrigin().x();
    double y_vect_d = transformed_corner_4.getOrigin().y();


    double door_x = transform.getOrigin.x();
    double door_y = transform.getOrigin.y();


double r_numerator = (cx-ax)*(bx-ax) + (cy-ay)*(by-ay);
double r_denomenator = (bx-ax)*(bx-ax) + (by-ay)*(by-ay);
double r = r_numerator / r_denomenator;

double px = ax + r*(bx-ax);
    double py = ay + r*(by-ay);

    double s =  ((ay-cy)*(bx-ax)-(ax-cx)*(by-ay) ) / r_denomenator;

distanceLine = fabs(s)*sqrt(r_denomenator);

// (xx,yy) is the point on the lineSegment closest to (cx,cy)

double xx = px;
double yy = py;

if ( (r >= 0) && (r <= 1) )
{
    distanceSegment = distanceLine;
}
else
{

    double dist1 = (cx-ax)*(cx-ax) + (cy-ay)*(cy-ay);
    double dist2 = (cx-bx)*(cx-bx) + (cy-by)*(cy-by);
    if (dist1 < dist2)
    {
        xx = ax;
        yy = ay;
        distanceSegment = sqrt(dist1);
    }
    else
    {
        xx = bx;
        yy = by;
        distanceSegment = sqrt(dist2);
    }