BEST METHOD FOR HIGH RISE CONSTRUCTION - GPS? ZENITH/VERTICAL OPTICAL PLUMMET? RESECTION

Greetings from Malta.

Malta

To those out there who had an experience of high rise construction, i would like to share some of your advice for the young generations. 

 

I am a qualified 28 year old land surveyor working with a construction company in Malta.

I will be involved for construction of a high rise construction project and it will consist of 4 towers of different floor levels. The height tower is 21 floors from the road. You need to keep into consideration that the facade will be constructed with glass material thus the accuracy should be within its tolerance when setting out the edge of concrete slab and also the lift should be kept vertically straight against deflection. As you can see from the development model, the construction is straight forward.

This is the first experience that I am going to get involved on such a big project and thus I need some professional advises to make a proper decision.

 

 

Attached are some pictures of the project for a better idea and also the location of the site from google map. You can type on google maps/search: Mriehel Gasan and you will find the exact site location.

 

 

I am not sure which method I am going to use for this project. After an intensive research I have not yet made my mind up for the best land surveying practices method for a high rise building do carry out the setting out of points and transfer the datum levels on each floor in terms of accuracy and precision and time efficiency. 

 

  • Using Zenith Laser Optical Plummet as per below instruments? Using this zenith optical plummet means that we must leave a vertical hole on each slab from the very bottom basement levels till the complete of construction. Am I correct?

 

  • GNSS method would be better, easy, more accurate and faster? I thought to use GS16 as a rover while I can connect with free of charge base reference station from Government Mapping Department. It is free because it was funded by the EU so it is public. Do you think this system will achieve its accuracy standard? I guess using an RTK system mounting the rover on the total station (smart total station) since setting out of hundreds of points with total station is faster (since laser helps a lot to guide the laborer to put nails). I saw a lot of surveyors in Dubai using GNSS system for high rise construction. What do you suggest?

Since there will be 1 crew (1 land surveyor which is me and 1 assistant/laborer) assigned on this project, do you think that using GPS is faster? Or still believe with the optical plummet? I have the feeling that the process of using the software spider or any other kings of software's is a long process because every time I do the setup and after starting the antenna to receive the signals, then I have to go all the way down the stairs to my mobile office do run the software, then back again near the gps/smart total station to commence the setting out. Am I right?

 

The purpose of the spider software is to adjust the control points to use the post processing method? I thought maybe I could use the RTK system.

 

 

 

  • The other method is resection. Let’s say I get a permission from the owners to install some ten 360 prisms on the building roofs so that I can use resection method. With total station I can setup and observe 4 stations which is orientation with resection by installing several 360 prisms on the top of the building when the construction reach its certain height levels but I am not sure the it will achieve its top accuracy with resection despite these prisms will be located away from the site about 300 meters or more. My question is about the accuracy and efficiency because I think for these 10 stations, somehow I need to carry out a traverse observations to adjust these stations.

 

 

  • Or maybe other method that I missed or product that I might not be aware yet?

 

I am really looking forward to hear from you guys. Thanks for your time and interest.  

This Content Originally Published by a land surveyor to Land Surveyors United Network

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ok. Thanks for helpful suggestions

i used the GNSS with static mode plus special sensors to measure the inclination in the building 

in another projects where GNSS signals quality is poor i used a special method called zenith line  application mounted at total station , and i can run it manually    

That's what we developed for you dear Kadmous ! 

Hi Christian ! We already had an extensive exchange on guiding high rise to the vertical and here is my contribution to the discussion. Resection (Free Station) using angles (directions) and distances to control points is as accurate as any other surveying methods and depend on the quality of your control points and the geometry. You can solve the problem by considering either the observations (angles and distances) or directly the 3D coordinates. In that case a "Free Station" is not more than a 3D transformation (Helmert) at 6 parameters as we assume the distances are invariant in space (and have been properly reduced/corrected from refraction etc, ...). You can place 3 - 4 360° reflector on the building top and use them from the top assuming you will determine the 3D coordinates of these points from the outside. But from the ground to the top it's not easy (at all). GNSS is providing excellent results (mm accuracy ... since the 90's) in post-processing mode and that is what we are doing in most of the high rises. RTK (that has been promoted by Trimble because they had to come to that business looking after Leica Geosystems) can be as accurate as PPK (Post-processing Kinematic) if properly filtered (which is not what Trimble is doing - they are not applying noise filtering techniques) BUT the problem is to get the position fixed ! And the building top in construction is NEVER an ideal place for tracking GNSS satellites due to cranes and placing booms. If you average PPK solutions over an hour you can however get mm results. That request some experience anyway. Laser plumets are still good ... but you need openings through the slabs and most of the time not that accurate (GNSS to that respect is much more accurate than trying to read the deflections of a laser spot on a target in a noisy and dusty environment). Setting up lines and traversing is honestly proven but past techniques. I have published several papers on Core Wall Control Survey method that I invented at first for the Burj Khalifa tower in Dubai. On the "top" there is also a patent on that method. Last not least, please don't be distract by the High Rise App from Trimble as they just copy and paste what they found in my papers. They also brought an old patent they put for a high rise built in Brisbane but the funny thing is that their App is not using what is on their patent. Isn't curious ? Not really. High Rise buildings are serious stuffs and certainly not "solved" with an App. The good news is that surveyors acting in such projects are very much respected by the engineers, consultants and architects because they will ask you all the time for more data ! All the best and greetings from Belgium.

Use two methods minimum  for cross check your points in each jumping 

it is depending on hights of building... in your case you can use optical and static GPs Analyses using Advanced software....  

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