Tuesday, July 26, 2016

Map transformations

MAP TRANSFORMATIONS

Map transformation involves transformation of points from one map to points on another map while minimizing the differences between the two sets of points.


  • The 'Helmert transformation' is the best choice for the vast majority of applications.
  • The 'Helmert transformation' translates the points of one map horizontally and vertically and also rotates and scales the points (it uses 4 parameters).
  • The 'affine transformation' is useful in cases where the paper has pronounced directional shrinking due to orientation of the fibers.
  • The 'affine transformation' is also useful to compensate for some shearing in the map or for computing the shearing angle.
  • The 'affine transformation' with five parameters translates points in the x direction and y direction, a rotation and two scale factors (one in the x direction and one in the y direction)
  • The 'affine transformation' with six parameters consists of:
    • translation in x direction
    • translation in y direction
    • two rotation and two scale factors (both axes are rotated and scaled separately)
Other map transformations used are:

  1. Robust Helmert
  2. Huber estimator
  3. Vestimator and
  4. Hampel estimator