As
you may appreciate the only 'true' vertical portion on the image
is directly in the centre (assuming the camera is at 90º
to the earth), as you move across the image a slight deviation
from the 'true' vertical occurs together with a phenomenon called
radial distortion. This has the effect of leaning the buildings
(especially tall ones) outward from the vertical centre.
Vertical
imagery is used in a wide variety of planning, coordinating and
cartography applications due to its consistent scale and high
image resolution and can be supplied as plain images, Geo or Ortho-rectified.
