[GRASS-dev] [bug #3296] (grass) i.rectify: automatic resolution calculation is wrong

[Cedric Shock via RT]

This is a differential geometry problem related to the Jacobian. You have a
map for rectifying:

(x, y) = f (u, v)

Where u and v are the coordinates in the image and x and y are the coordinates
in the location. For the x resolution you want to find the smallest amount x
changes when u or v change. For the y resolution you want to find the smallest
amount y changes when u or v change.

So you want to find the minimum of (d is delta for partial derivatives):

(dx / du) (f) * u-resolution
(dx / dv) (f) * v-resolution

for x resolution and

(dy / du) (f) * u-resolution
(dy / dv) (f) * v-resolution

for y resolution.

You only care about these minumums over the existing u and v values.

-------------------------------------------- Managed by Request Tracker