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.  

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High rise surveying is over my head. Lol sorry

ok thanks. Thanks for your time. 

All depends on the control you have to come from. Stay away from resection. Do not use GPS. Pick a control line and stick with that one control line...if you can't set up rectangular control lines for each of the buildings. Use a total station and only use that one. Make sure it's calibrated both horizontally and vertically. Make sure you know if the compensators are on or off. Get a 90 degree eyepiece if you are plumming the steel.

ok. Thanks for your suggestions

RTK GPS is not accurate enough.

Vertical laser is not accurate enough also. There are special optical plummets (zenith/nadir) used in mines, but if you have not used those method before it will be better to choose the total station.

Use a very accurate (1", 2" or at least 3" but not worse), calibrated total station as ROB ROSA mentioned before.

Resection is not the most accurate solution, but better than the RTK.

If you can use more than 2 points for resection, it may accurate enough, if your control network is very precise, but don't forget, as the building grows higher, it will be difficult to measure 2-3-4 points for resection, and if you can see 2-3-4, they will be nearly the same direction (worse geometry), except on the corners.

360° prism are not as accurate as the single prism or the reflect foils, so I recommend you to use normal prisms.

Setup your instrument on the ground level and establish some control points on each floor. It would be better if your points are located far from each other, adjacent side of the building (at least two, but more is better). Then you can use your control points as station points, and for backsight as well. You must check your network on each floor using backsight points on the same floor and on the ground level as well.

That's a really interesting article on the Leica control wall, Billy. Thank you... Every day a school day!

useful post. thanks.

Thanks for sharing. Really helpful 

Thank you , Christian

Thank you Paul for the shout back,always good to here.

Billy

hi

as stated Rtk is not really a good tool to control the high rise buildings.

try to use min 3 plumbing points ( slab opening) & plumb them up to your active slab using laser plummet or with total station .

u have to coordinate with your structural engineer to finalize the location of your plumbing points.

once the points location are defined make sure all the points are best fit to each other as well as, with the primary control points.

u could spread out your primary control points around your plot limits to keep a cross check each time u set up your instrument. try to setup wall mounted prisms in surrounding building at maximum height for better view and availability.

resection is always much more accurate and convenient than keeping a base line or sticking with back sight method.

dont forget to check the inner constraint of the plumbing points each time u shift them up the next floor.

best of luck 

Sarfraz

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