AccuLine 40-6910 Manuel d'instruction - Page 9

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7/29/09

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Page 9

5.5 Determining difference in elevation

Measuring a difference in elevation from one set-up

To find the difference of elevation between two points which can be

observed from one position, set up and level your instrument about

midway between these points. Be sure that a leveling rod held on

both opposite points can be read when your telescope is level. Each

point should not be greater than 150 to 200 feet away from the

instrument or you may have difficulty reading the rods. The height of

the line of sight (horizontal crosshair) above or below each of the

points is found by reading the rod.

A line of sight 69 inches above A and 40 inches above B is shown

above. Therefore, B is higher than A by 29 inches.

Suppose one of your points is below the line of sight and the other

above (Fig. B), C is 4 feet 6-1/2 inches below the line of sight, and

point D, the underside of a floor beam is 7 feet 9-3/8 inches above

the line of sight (the latter reading having been obtained by holding

the rod upside down with the foot of the rod against the beam). D is

then higher than C by an amount equal to 4 feet 6-1/2 inches plus 7

feet 9-3/8 inches, or a total of 12 feet 3-7/8 inches.