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Highrise surveying

1. Establish an envelope of building lines at flat convenient offset that will not be destroyed in process of building.

2. Close the figure and prorate grid line intersections, prefer steel chain with temp and spring tension.

note: to save time you may prorate by tension (pulling till it fits, and holding that pull) or by PPM adjustment on some total stations (changing PPM's till overall fits then shoot intermediate with mini prism)

3. make sure you measure grid to grid and no more then .005 deviation, or correct.

4. looking from one side of building to the same grid on the opposite side throw back lines to safer area and top of buildings or other natural sights, for future use.

5. set convenient offset to grid line far enough away to avoid columns and close enough to set gun on column clamp (aluminum angle plate with slot to attach instrument and 2 "C" clamps to clamp on column when you get up in building)

6. Set up on offset have helper go to floor you need control after giving sight on opposite side of building and marking or putting nail for temp site on barricade for you to check into, or use tripod and tribach, sight the point making sure your plate level is centered,  (digital in many) and point the gun upward to your helper. Helper should have an offset sight (for the same offset) ((must have 90 degree eyepiece as you get higher))

sight can be folding ruler with paper target on offset (plus 1' if using 2' offset) direct him until target is good, then he can mark the 1' mark on the folding ruler (can also be a story pole) anyway, now reverse the instrument and relevel, resight and redirect him. Have him split the marks (should not be more then 0.01' in most cases.

DO THIS IN EARLY MORNING BEFORE SUN AFFECTS BUILDING AND BEFORE WINDS KICK UP.

7. After spiting the error, take the split down to the previous floor, should not be more then 0.02, if it is, you may have to adjust to previous floor if your floor is already poured. Craftsmen can easily detect 0.02' between floors and they will lose confidence in your work, not to mention backcharges that may result.

8. After placing all the column and row lines you will need on that floor, clamp your column clamp on one side and set instrument on necessary offset, backsight the other side of floor that you marked and either place marks on columns using story pole or mark concrete or decking or form at required offset on deck.

9. Take your chain and measure up from your crowfoot mark on bottom floor for benchmark. Remember pull about 10 pounds to get kinks out of chain, dont worry about temperature correction just make sure it is the same temperature as building (compensating error). Also keep the bench marks in the side away from the sun and perhaps the elevator shaft, take up three and always check between all three before setting the rest for the floor.

10. By setting the level at the height above finish floor you are setting you can adjust minute amounts using the screws and then scan the rest as your helper marks them.

Notes:

Building leans away from the sun, get your outside work done early.

Buildings settle (see your geology report) so dont be surprised when your ground floor marks on columns go down a little , if they go down more then 0.02' ask the contractor for direction, eg does he want your to redo all the ones in the upper floors and match the new bottom or will he handle it on the ground floor etc.

in other words CYA

If your working concrete, expect challenges from carpenters, they think they can do everyones job, remember the old adage "measure twice, cut once".

The more pressure they put on you the slower you must go, this is not an option, pressure creates mistakes, mistakes causes other crafts to lose confidence in surveyors, you are duty bound to your craft (3000 years old) to never, never, never let them lose confidence in what we do. When backed into a corner, say "I need to recheck the plans", or "let me recheck my instrument". Learn to give as little as information as possible concerning why, what or how you do your work, and remember, everyone is replaceable.

Above all keep safe, pray every day for a safe job (it works). Do not depend on the perimeter cables. attach your safety harness to the one you will not be holding on to, check the tension on them, sometimes the guy bring loads into the building finger tighten the nuts, I know, I fell off the 5th floor, because of that, but by a miracle of God I am alive today.

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  • Thanks for sharing your view .one I have to add you have to add at list 1 mm more in floorr for settlement .other wise one would get problem with shorting of building
    • I have seen major buildings set on hundreds of piles settle a centimeter. You need to refer to the geology report which should give a value for settlement after the building is fully loaded.

  • Seeking Employment

    Thanks for sharing sir! Any suggested books?

    • I take only credit for adding the "prorate by PPM and prorate by tension" everything else I was taught by other surveyors in Los Angeles. Including praying everyday for safety.

  • thanks for sharing...

  • Survey Legend

    Thank you for sharing this Michael..  I am sure there are many who will find it useful.

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