Point clouds: Model or Design?

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Sandy.Walker
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Point clouds: Model or Design?

Post by Sandy.Walker »

Hi there,

I have been asked to find the best (accurate / fast / cost effective) way(s) to have off-shore rigs surveyed, destructed and redesigned. I am to find the best way to use survey data to provide a means to model from. Currently I am led to believe that there are at least a couple of ways of doing this.

First method
For larger areas:
1. Laser scan survey produces a point cloud
2. Point cloud is sent to be fully / partially modelled (long process)
3. CAD model is used for redesign purposes

Second method
1. Laser scan survey produces a point cloud
2. Point cloud is used to design from directly (not quite sure how this works, from using several software packages it seems difficult to understand location when designing)

I have seen semi-automated & automated cylinder modelling using part libraries but for purposes of design, an intelligent model is not required. Of course it could be useful for other applications however.

Does anyone have experience in this area that could help?

- Sandy
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Phill
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Re: Point clouds: Model or Design?

Post by Phill »

Sandy

We do a lot of this type of work, not on oil rigs, but other material's handling infrastructure, for example conveyor transfer stations and sewer treatment plants. The two methods are both valid.

First Method
We tend not to use the fit to cloud method as it is a very time consuming process, but rather place the objects in by eye. This allows for to put the objects on a grid system, which makes it easier to design off, but also allows us to identfy beams that are not uniform. Most of the time we use this method for engineers doing smaller style projects, where the expertise in CAD is not availble. A single person can model approximatly 250 objects a day, which gives a good indication of how much work in involved using this method.

Second Method
On big projects, where there will be huge amounts of data and objects to be extracted, we often have engineers/ drafts people who understand the cloud and how to measure from it. In this case, mostly for retrofits and upgrades, the engineers themselves will extract only the essential peices that they require on an as needs basis, using an "in CAD" package such as clouworks or pointools.

Hope this helps

Cheers

Phill
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Re: Point clouds: Model or Design?

Post by Sandy.Walker »

Thanks for the quick reply Phill,

I was fairly sure that the second method was likely to be the best choice as most of the projects are fairly large scale, but my lack of knowledge in modelling piping etc. is hindering my understanding of the necessary methods.

Just to see if i've got this right, the engineers / designers are using the point cloud to model their piping / structural work through. I assume this includes no CAD objects, though I suppose there is some clash checks done on new geometry against the pointcloud? Are key elements modelled or just measured from? (like modelling away from a flange say)

I'm fairly new to almost all of this, so apologies for the really newbie questions :)

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Re: Point clouds: Model or Design?

Post by Graham »

I Plant design packages like AVEVA PDMS and Intergraph's product the laser data (point cloud) is rendered in the design enviroment and new elements are clashed against the point cloud.

Images of laser data and design geometry
http://www.scopuseng.com/case-studies-case-7.htm#View

Images of laser data highlighted in red to identify clashes between design geometry and a point cloud.
http://www.aveva.com/Products_and_Servi ... A_LMI.aspx

The designer can make measurements such as a point to point measurement to check dimensions like the web and flange of steels. Most systems offer for piping the ability to click on the laser data of a pipe and the system will return information on the outside diameter, its orientation and centre line.
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Re: Point clouds: Model or Design?

Post by Phill »

Sandy

Using the second method, most of the time objects are modelled, using the existing design packages, such as the one Graham mentioned, with cloud overlayed. Often the model is made from the exisitng drawings, and then the critical pieces are adjusted to the cloud, but sometimes all that is required is a measurment from point to point. In this case the measurement is taken directly from cloud. It sounds like you are planning to do pipework, which can be tricky as the pipes often dont run on a site grid. A lot of the pipework we do is completely modelled in a more dynamic 3d environment, such as Cyclone.

Cheers

Phill
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Re: Point clouds: Model or Design?

Post by Sandy.Walker »

Phill,

When you say completely modelled, are you talking about modelling existing geometry or creating new pipework? I have only had a brief look into Cyclone before but i'll definitely have a better look now. I think again the problems the designers may face using the cloud directly is the lack of clarity (knowing where they are / what they are looking at). I don't and I know they don't have a huge amount of trust in measuring directly from point clouds. I certainly haven't found a quick way of selecting the required points without having to check there is no ambiguity in the point's location.

Certainly piping is one of my main concerns but I hold hope to find something useful for the structural guys too.
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