RELIEF DISPLACEMENT

Relief is the elevation of object above or below the datum. Relief displacement is the lateral displacement (also called as shift) in the position of image on the photograph of a ground object. If the object is above the datum, relief displacement is outwards, whereas, if the object is below the datum, the relief displacement is inwards.

R (H – hA) = r‘H
r – r’ = rhA /H
i.e.             Relief displacement, d = rh/H
where             h = Height of the object above datum
H = Flying height above datum
r = Radial distance of the image of the object top from point O

• The relief displacement ‘d ’ increases with an increase in the elevation of the object above the datum. It decreases with an increase in the flying height above the datum.
• It is useful in determination of height of various objects such as buildings, poles, chimneys, etc.

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