SETTING OUTSETTING OUT

Horizontal Angles

Horizontal Angles

Horizontal Angles• Ensure instrument is set to measure angles in the

appropriate direction. ( refer to operators manual)• Unclamp both vertical and upper horizontal clamps.• Ensure lower horizontal clamp (if fitted) is locked.• Use target finder to locate reference target station

keeping one hand on horizontal clamp. Clamp in smooth operation when target located.

• Look through telescope and bring target into focus. Start with focussing ring turned fully one way then will avoid “missing” focal point.

• Use Horizontal and Vertical tangent screws to bring stadia lines over target.

• Ensure that target is vertical or use the lowest point visible.

Target

Set angle

• Zero set instrument (refer to manual)• Unclamp horizontal clamp and move instrument

round until digital read out is within 1 of desired angle.

• Clamp horizontal and use tangent screw to adjust digital read out to desired angle.

• Be aware of accuracy of instrument. (typically 5”)

• Give arm signals to assistant to locate ranging rod in desired direction.

• Target the point of the ranging rod.

Assistant’s role• Stretch out tape ( or accurately pace) in viewing

direction• Hold ranging rod vertically at approx set out

distance.• Follow arm signals from engineer• NOTE: Do not move rod haphazardly. Bisect

the difference between rod movements. This will very quickly get you to the correct direction.

1st 2nd3rd 4th5th

• Replace ranging rod with stake – hold stake centre-line adjacent to correct measurement on tape and drive stake in vertically.

• (ensure that the tape is held approx level OR use calculated sloping distance)

• Place tape on stake head and mark, with a pencil, an arc of radius equal to setting out distance. (slope corrected if necessary)

Assistant’s role – Taped measurement

• Move nail across arc and follow engineers arm signal to get correct direction.

• Mark nail position to make a cross with previously drawn arc.

• At this point the Engineer will transit the telescope and repeat the angle setting out in the opposite face.

• Follow the engineers arm signals and then mark a second cross on the previously drawn arc

• Bisect the difference between the two crosses and drive in a nail vertically

Assistant’s role – Taped measurement

• Once on correct line, replace ranging rod with reflector prism on short spike.

• Set spike to approx distance and follow engineers arm signals for moving back or forward. (Bisect difference as for transverse movements)

• Mark ground and drive in vertically a stake at this point.• Repeat location on stake head and mark with pencil.• At this point the Engineer will transit the telescope and

repeat the angle setting out in the opposite face• Locate and mark a second point on the stake head.• Drive in a nail half way between the two crosses.• Check distance to the nail.

Assistant’s role – using EDM and Reflector

Face I and Face II• Once the engineer has located the stake

out point in face I setting he must repeat the same operation in the face II setting.

• This eliminates any collimation errors due to the vertical axis not being truly perpendicular to the trunnion axis.

Face I Face II

arc

Nail centred between two marks

Final check• Once a mark has been set out, before

transiting the telescope, the engineer should return the instrument to target the reference station and check if the digital display again reads zero.

• This should be repeated on both faces.