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Please, can someone give me a clue on how to carry out verticality check on a tank farm using a total station and also how to analyze the data to be able to present it to a client.
This Content Originally Published by a land surveyor to Land Surveyors United Network
This may require one to simplify his thinking. It needn't be complex and I doubt an "app" was made to do it (but who knows ... maybe).
Can you access the inside of the tanks? If so you might treat it a bit like checking the square-ness of slab forms. Measure from the top at a spot to the bottom diametrically opposed, repeat around the tank.
Another is to hang a plum bob from the center ceiling. check distant from the bob to the walls of the tank high and low. They should be the same all around in a symmetrical tank.
Externally, your choices may be restrained by size and layout of the tanks. Many scans with a LASER scanner to build a strong point cloud might do. I would insist that a plumb bob or plumb rod be included in many of the scanned images. You will be able to test against the plumb references throughout.
A tedious external method might be to set up a theodolite around a tank (several set-ups) and very carefully level the instrument. then sight the 2 tangent vertical lines of the tank to you left and to your right. Move the set-up and repeat until satisfied.
A third might be, with access to the roof of the tank, to build a simple contraption to hold a plumb bob a few inches our from the wall and check the distance is consistent by tape of other means. Repeat around the tank until satisfied.
Thanks for your contribution......i think the second to the last will be most suitable for the operation..since i cant access the inside of the tank
When I was working in Indonesia on the Caltex oil fields on the island of Sumatra, we did this check, on large tanks, by placing 8 targets around the top and another 8 around the bottom, spaced about equally by taping. The upper targets were set vertically above the lower by a total station. Stick-on reflective targets work best. We then ran a 4-sided traverse around the tank with stations approximately opposite every other target. From each traverse point measure angles and distances to the 3 visible targets. We put all measurements into a least-squares adjustment program. A best fit circle was computed for both the top and bottom targets. The report showed deviations from the circles, the offset from radius points, and radial offsets between the top and corresponding bottom targets.
thanks for your contribution....please i will like to get something clear....are you suggesting i coordinate many points on the tank and plot the coordinates in autocad?
If you have prism less 1second TS you can observe the base point and the top point. From these points you can compute or compare the xy coordinates to check if the result is within the allowable error.
If you can approach the top edge of the tank you can use plumb bob, to avoid wind effect the string of plumb bob can be inside a pvc pipe. You can also use the vertical cross hair to check the vertical alignment of the tank.
Show your computation to the representative of your client, the representative must be a technical person to understand the data. Another thing let the representative do the sighting using the TS to let him know the vertical alignment of the tank.
The simplest reference for verticality is also the easiest to convey to a client - a plumb bob (in windless conditions).
Include the plumb bob in your scan and you have the perfect reference for comparison.
All other "control" methods have at least 2 dependencies vs. this direct one.
If too windy to protect, then a plumbed range pole. Note: most range pole bubbles have not been checked in ages. Check and adjust the bubble before trusting it.
That is a tough question. You could use a laser scanner instead to scan the tank and check the vertically. The total station would be used to set the control points for the scanner and the spheres. I hope this helps.
The basic thing to do would be to Set control stations around the Tank then use reflector less EDM mode to measure the RL at the bottom of the tank and directly on the same horizontal angel measure one at the top of the tank. You don't need a software but just the difference in the heights should give you the verticality that you need.
Hope this helps.
If you want to show the data to your client, would be better to use some SW, for example RHINOCEROS (I used it on the oil platform for analyze the same kind of data), CATIA, SOLID WORK and others. With those SW you may analyze the 3D data and prepare a report. About the survey with a total station I agree with Tom Ameson (you can also measure a lot of vertical sections that you highlighted before on the tank's surface ) and analyze the data with the SW listed above. You can verify the verticality and also the squareness.
thanks for your reply