Precisely measuring Spheres location with a Total Station

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pedropcsena
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Precisely measuring Spheres location with a Total Station

Post by pedropcsena »

Hi everyone,

I am new to this forum, but I have read a lot of good advices from all the discussion that has been posted here :D .
I am working with a FARO X330, and I am new with this technology, however I have a solid understand of geomatics overall, and I have done photogrammetry & land surveying projects as well.
I will be using the scanner for Surveying purposes, so my measurements need to be tight to a certain level. I have been running many tests, setting up the scan in different positions, trying different registration methods, georeferencing, and everything seems to work really well so far. I measured points with the total station, set 3 of these points as control, and used the other points as check points and I am within the acceptable tolerance I need (1cm +/-).

My main question is, when I measure the location of the Checkerboard with the Total Station, I shoot (measure) the point right in the middle, which is the connection between the two squares. But for the spheres, how do I measure the actual position of the sphere? The sphere has a diameter of 14cm. I could "try" to measure the centre of the sphere, by measuring its centre and offsetting it by 7cm, however, as much as I try to aim to the centre of the sphere(reflectorless), there is no guarantee that I am actually measuring the centre location of the sphere that I am looking for. If I am off by 1cm, and I use this sphere as a control for georeferencing, my points will get screwed up :? Which way is the most accurate way of measuring this?

Also, I will start a big project soon, so I will be scanning for a full day, and the other day I will preprocess the data. I will be doing this until the project is done (1 field day, 1 office day, 1 field day, 1 office day, and so on...). Main question is, from one day, to another, which kind of targets are ideal to do "resection" ? For now, I am thinking of drilling a hole in the wall and set my spheres. But my concern is that the client won't let me drill the wall. Another thing, I could set the Checkerboard, but after 2 days there is a big chance that someone will remove my target from its location. What are you suggestions?

Thank you very much,

Pedro
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Re: Precisely measuring Spheres location with a Total Statio

Post by jcoco3 »

Pedro,

You may find this somewhat helpful:
http://www.laserscanningforum.com/forum ... =49&t=5618

http://www.laserscanningforum.com/forum ... =20&t=9895

Long reads, so you may want to skip through to the relevant parts near the end.
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Re: Precisely measuring Spheres location with a Total Statio

Post by uberto »

You can measure spheres with a Totalstation indirectly with eqipment from "Laserscanning Europe"....special sticker on steel....magnetic adapter with special reflector....costs of some hundred Euro....or if you have a 3D printer....you can print your own...we made tests with our selfconstructed sphere...middle of the two measured points is center of sphere.... accuracy Totalstation / Faro Scene....1-2 mm.....total costs for one sphere....under 15 Euro.... :D
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pedropcsena
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Re: Precisely measuring Spheres location with a Total Statio

Post by pedropcsena »

jcoco3 wrote:Pedro,

You may find this somewhat helpful:
http://www.laserscanningforum.com/forum ... =49&t=5618

http://www.laserscanningforum.com/forum ... =20&t=9895

Long reads, so you may want to skip through to the relevant parts near the end.
Thanks Jonathan, really good post. I will definitely start looking for a prism asap so I can run some tests. Much appreciated.
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pedropcsena
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Re: Precisely measuring Spheres location with a Total Statio

Post by pedropcsena »

uberto wrote:You can measure spheres with a Totalstation indirectly with eqipment from "Laserscanning Europe"....special sticker on steel....magnetic adapter with special reflector....costs of some hundred Euro....or if you have a 3D printer....you can print your own...we made tests with our selfconstructed sphere...middle of the two measured points is center of sphere.... accuracy Totalstation / Faro Scene....1-2 mm.....total costs for one sphere....under 15 Euro.... :D
That is awesome. I think this is the best quick solution for me since I will start the project next week. If I am not asking too much, do you have the .stl or .obj file that I can directly send to the 3D printer? Since I just finished school, some friends might be able to hook me up with that design for free. Thank you!
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Re: Precisely measuring Spheres location with a Total Statio

Post by uberto »

Pedro,
find attachhed the stl file of the sphere...diameter 140 mm....you can buy a threading bush for a connection to a photo tripod and glue it into the sphere....you have to construct the "ears" for yourself and play with different diameters depending on the accuracy of the 3d printer....make sure that the surface of the "ear" is in the center of the cylinder..... ;)
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pedropcsena
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Re: Precisely measuring Spheres location with a Total Statio

Post by pedropcsena »

uberto wrote:Pedro,
find attachhed the stl file of the sphere...diameter 140 mm....you can buy a threading bush for a connection to a photo tripod and glue it into the sphere....you have to construct the "ears" for yourself and play with different diameters depending on the accuracy of the 3d printer....make sure that the surface of the "ear" is in the center of the cylinder..... ;)
Thank you so much! That is really helpful. I will let you know the outcome of it!
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