Hitachi ZAXIS 120-6 class Operator's Manual page 212

Discrepancies between Image and Actual Road Surface
1) Images of Ascending Slopes or Faces
This indicates how the camera looks when shooting uphill.
Because point (a) on the upslope is stretched on the
monitor screen on an extended line of the plane, the
distance from the vehicle icon is depicted as further than it
actually is.
2) Images of Descending Slopes or Cliffs
This indicates how the camera looks when shooting
downhill.
Because point (b) on the downslope is shortened on the
monitor screen on an extended line of the plane, the
distance from the vehicle icon is depicted as closer than it
actually is.
OPERATOR'S STATION
1-130
Actual Position of Point (a)
Position Point (a) Appears Onscreen
Position Point (b) Appears Onscreen
Actual Position of Point (b)
Slope
a
MDCK-OP3-021
b
Slope
MDCK-OP3-022