Kindly help me.. i am a Survey Engineer and it is my first time to handle a HIGH RISE building 30 storey.. I am thinking, when i reached 15-30 floors.. how can i transfer points from ground to those floors.. kindly give me some advise. or steps.. it will help me a lot please...
This Content Originally Published by a land surveyor to Land Surveyors United Network
Two assumptions to start with:
1. This is a steel structure and your concern is STRAIGHT UP.
2. You have "quality control checked" and know exactly where horizontally your steel columns are setting to the nearest hundredth. AND you have reviewed your "asbuilt" findings with the project
superintendent. This takes care of your "CYA". OK!
Once the bottom floor columns are in place, FORGET ABOUT GROUND CONTROL--DON'T EVER
GO THERE AGAIN.
Most vertical steel columns come in "two-floor" increments with a splice just above the 2nd floor.
On the ground floor set a TOPCON prismless total station on your tripod. Remove the eye piece and
attach a 90 degree eye in its place. With out this equipment----forget it---your not going to get the job done. Once done with the ground floor set-ups get rid of the tripod also.
Here is your process. Assuming they are erecting sections of the building of about 3 columns wide
by 5 columns depth and remember it is two floors at a time vertically.
Set your tripod and Total station on the ground floor just off line with the nearest column your shooting in
the row of 5 columns such that you can see part of the flange of each column AND you can see the bottom of each column and the top of each column just below the splice--WARNING: make sure you are
not shooting the splice plate----only the column flange. Level up your insturment and your ready to go.
Get an 8 1/2 by 11 sheet of paper on a clip board with the column symbols laid out with plenty of space
between for shot notes. Be sure to properly label this sheet AND never let it get away from you---give out only copies to the steel workers and your boss.
You will be recording shots twice: once on the intitial erection AND on a clean sheet for the final asbuilt
when the steel crew is "cranking" the adjustment cables. The steel crew will use your first shot record
to determine where they need to erect adjustment cables. You aim the gun just a few inches above its base and lock the horizontal; then shoot the flange by pushing the H DISTANCE button on the gun. record
the average of several shots. then carefully raise the scope without moving the horizontal to just below the splice plate (two floors up). This probably should not be more than about 45 degrees off horizontal. Now
push your DISTANCE button several times and record the distance; It will be either closer to you at the top or farther from you. Now unlock your horizontal and put your vertical eye hair at the edge of the flange
near your top shot and lock the horizontal; then lower the scope to the base; have someone put a tape aganst the edge of the flange and read it through your scope: that is how far it must move in the perpendicular direction at the top. Be sure to record this just in case the steel crew doesn't want to move it---show it to the boss---it will mess you up going on up.
Now! Once off the ground floor have the steel workers cut you two 3x3 angle irons
that have bolt holes to attach to any column with a welded plate to mount the gun too.
Be sure to give yourself about 1 1/2 foot from the center of the gun to the near edge of
the flange. Just keep doing this as you go up---over and over. Have fun.
Another way, a little less complicated, can be RESECTION on each floor using your Total Station, just be sure the Ground Control Points are VERY GOOD, this is maximum 3 mm Residual difference and 1" angle residual difference, check all your GCP, then you can set your Control Points on top of the adjacent buildings and GO...
what do you mean by "contol point shoud not be ondanger circle"
The rule of thumb to do Resection the angle between GCP must be minimum 45 degrees
I use to do minimum 90 and if possible more than 135.
thanks guy, any more comments?
Everything looks nice but... remember that the structure will be moving, wind, transit, things going up and down, etc. have you ever seen a plumb holding about 50m or more??? the same will do your instrument doesn´t matter the brand.
I would do the vertical control with total station from the ground if possible, then you can place control points on each "floor" by GPS 24hs sesion, and from there measure distances to columns.
I have seen 10 floors buildings made with a plumb, a can, and some oil that pass a total station control quite well.
By 24hs I meant various short sessions covering all the day.