Sokkia B20, Operator'S Manual, Page: 42 / 60

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6. OPERATION
6.1 MEASURING HEIGHT DIFFERENCE
1) Set up the instrument at a point approximately halfway
between points A and B (Fig.6.1). The reticle stadia lines
can be used to optically compare the distances. (See "6.3
MEASURING DISTANCE USING THE STADIA LINES"
.)
※
For more accurate measurement, set the instrument as
close to halfway as possible, to eliminate errors due to
sighting axis misalignment.
Fig.6.1
2) Position the staff vertically at point A.
Take the reading a (backsight) on the staff at point A.
3) Then sight the staff at point B and obtain the reading b
(foresight).
4) The difference a - b is the height difference h of B from A.
Example:
h = a - b = 1.735m - 1.224m = 0.511m