velocity.cc

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/*
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#include <semanticmodel/velocity.h>

namespace semanticmodel
{

namespace gm=geometry_msgs;

using std::string;

// three point one-sided interpolation for first derivative
inline
double deriv (const double y0, const double y1, const double y2,
              const double inc)
{
  return (3*y0 - 4*y1 + y2)/(2*inc);
}

// Lookup tf transforms at times t, t-inc, t-2*inc, and interpolate
gm::Vector3 VelocityCalc::velocity (const gm::PointStamped& p) const
{
  tf::Point pts[3];
  const tf::Point p0(p.point.x, p.point.y, p.point.z);
  const double t0 = p.header.stamp.toSec();
  for (unsigned i=0; i<3; i++)
  {
    const double t = t0-i*inc_;
    const tf::StampedTransform trans =
      transforms_->lookupTransform(reference_frame_, p.header.frame_id, t);
    pts[i] = trans*p0;
  }
  gm::Vector3 v;
  v.x = deriv(pts[0].x(), pts[1].x(), pts[2].x(), inc_);
  v.y = deriv(pts[0].y(), pts[1].y(), pts[2].y(), inc_);
  v.z = deriv(pts[0].z(), pts[1].z(), pts[2].z(), inc_);
  return v;
}

} // namespace