qgsAffine: Affine Transformations
Apply affine transformations to selected geometries.
This Quantim GIS (QGIS) plugin performs affine transformations on layers or a group of features.
For those infamiliar with affine transformations, here is the basic concept.
(x,y) can be tranformed to a new point
x' = a * x + b * y + tx y' = c * x + d * y + ty
ty are the translations in the x- and y-direction, resp.
d form the transformation matrix
| a b | A = | | | c d |
that determines the rotation and scaling.
ty are the variablesthat can be changed in the plugin.
Details on how to find the correct values for your case can be found anywhere on the Internet.
By default, the translations are zero and
T = I (the identity matrix), i.e.
x' = 1 * x + 0 * y + 0 = x y' = 0 * x + 1 * y + 0 = y