Scan to BIM: Point Clouds ReloadedKelly Cone - Beck Group

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Now that you have taken the Red Pill, you will need some training to be "the One" at your firm who understands how to work with all this point-cloud mumbo jumbo. Starting out in Autodesk® Revit® software, we will show you how to link point clouds and show you what the pitfalls are. We will show you how to manage the potential impact on view performance and the best practices and tools for modeling in your new virtual reality. We'll also introduce you to some plug-ins that let you do a lot more when modeling than Revit can do natively. We will bridge the paradox of either modeling with too much detail or creating a model that is too generic. And, finally, we'll take a quick spin in Autodesk® Navisworks® software to help you understand that sometimes you don't need to model everything (and even have you jump off a building or two while we're in there. Don't worry. You won't get hurt. We'll have collisions turned off). If you can make it through the training, you'll be ready for the revolution.

Learning ObjectivesAt the end of this class, you will be able to:

Understand file formats and point coloring options when working with scans

Link in massive point cloud files without destroying your model

Describe the various tools and techniques for using point cloud files to generate BIMs

Understand the advantages and pitfalls of simplifying the point cloud to a BIM

About the SpeakersKelly Cone: Kelly joined the Beck Group as an architectural intern and has been focusing on technology and implementation of BIM practices and software since. In his current role as Innovations Director, he oversees the implementation of BIM technology and processes nationwide in our Architecture, Estimating, Real Estate, and Construction groups. He is responsible for ensuring that the tools and technologies employed further Beck’s commitment to integrating the design and construction disciplines, and advance our efforts at making our buildings more sustainable. Kelly is also deeply involved in the Building Information Modeling community. He has spoken at numerous national and international BIM conferences and blogs about the future of BIM and the Revit Platform on RevitFutures.blogspot.com

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Class Outline:We are going to walk through the key topics below in the time we have. Having worked on many scanning projects, we could probably talk as a group about each of these headings for 20 or 30 minutes a piece, but that wouldn’t give us a chance to get through them all. Hopefully we will have time at the end for some good Q&A so we can get into some more depth with any specific concerns or questions from the audience.

Intro (5M) Getting Started with a Scan (15M) Linking Scans into Revit (10M) Working with Scans to Model Natively (10M) Must-Have Plugins for Scan to BIM (15M) To BIM or not to BIM (5M) Scans in a coordination environment (15M) Q&A (15M)

IntroductionSo, if you were in my class last year at AU, this was the class I wanted to teach. However, due to scheduling I decided to do an introductory class last year. Unfortunately, we couldn’t get the description changed in time so it was a little confusing for some people in the audience. Don’t worry, this year everything lines up! For those who did not make it last year or are new to laser scanning and want some basic information, here is a link to a mind map from last year’s presentation:

There are some notable things to mention at AU regarding point clouds and Autodesk software. Autodesk has made an acquisition of Alice Labs, and I expect to see a lot of very positive changes in how all Autodesk’s AEC products work with point clouds in the near future.

Also, I want to throw out one big caveat. At Beck we only work with Leica scan data. That means all our experience with these tools is based on Leica formats like PTS and PTX. There are other formats supported by both Revit and Navisworks and some settings and options will be different. I believe that the same general rules we share here will apply to the other formats, but there is always something different. If you’ve got experience with another format and your work in that format has lead you to a different experience, please speak up! One thing I love about AU is that I usually learn a lot from the attendees in my class – it isn’t a one way street.

Getting Started with a ScanSo, you’ve got a scan back. Now what do you do with it? Get it into your software of course! Naturally, it isn’t as simple as clicking a button. What do you need to worry about? How do you do it?

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Coordinates, coordinates, coordinates…With scanning, you live and die by coordinates. Sometimes for very small scan jobs cloud to cloud registration and non-located scan files are acceptable. But, for any big scan job survey and control are going to make your scan files reliable, and that means a located scan. Whether you choose state plane coordinates or to instruct your scanning crew to use a local coordinate point (like a known grid intersection and elevation as the origin), defining a coordinate system that will work for your field and your BIMs is critical. Once everyone agrees upon what that is, you *should* be able to get your scans to come in to the right spot with no fudging.

UnitsUnits are another important discussion for scanning deliverables. For instance, did you know that there is an actual difference between survey feet and international feet. No, that’s not a set up for a joke. Back in the day, a “foot” was not precisely defined as the same everywhere in the world. In the US we defined a foot as 1200/3937 meters. Meanwhile, the British foot was something else, etc… In 1959 the world got together and agreed on a standard value (sort of) of 1 foot = .3048 meters. However, some bonehead decided that within the US any survey data expressed in feet for geodetic uses would continue to use the old definition. Unfortunately for us, this means that a survey foot is different than an international foot. One international foot equals .999998 US Survey Feet. I know it seems like a tiny difference, but size does matter (also not a setup for a joke). When you’re dealing with state plane coordinates (values in the millions of feet) this tiny difference can be a bust of quite a few feet. On one project, the difference between the two was over 40 feet. So, although the survey was correct, the shared coordinates in the project were correct, and the scan was correct, nothing lined up. So, units really matter.

Because of the confusion, I’d like to switch over to metric across the board permanently. (Please, no one throw and shoes at me unless they will fit my feet – Men’s size 12 by the way, well, size 12 US.) Since that is unlikely to happen, you need to be aware what you’re setting up your project in. Likewise, it would be nice if the software companies (ahem…Autodesk?) would allow us to define shared coordinates and import unit settings by feet AND US survey feet until we all go metric. If your software supports importing/exporting using metric values for scan data, I highly recommend using it since meters are the same any way and any where you slice them. Reliability is a wonderful thing.

ColoringPoint clouds have several options for coloring depending on the program you’re using. Natively, the scanner captures not only the X, Y, and Z, values of the data point, but also the intensity of the reflection of the laser. Technically, more than just this is recorded, but as it relates to point coloration it’s the intensity that matters. Additionally, you can map photographs taken by the scanner or by a higher end camera rig onto those points. From those data options, you can usually do a couple of things:

Color mapped Intensity (maps the intensity value to a wide color range)

Grayscale intensity (maps the intensity to a grayscale value)

Coloration based on the mapped photos

Color ranges based on X, Y, or Z values (maps the dimensional value to a color range)

The more advanced tools give you many more options, and some tools (like Revit and Navis) that are new to the game give you less.

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CullingLast but not least, culling is a very important topic given today’s technology. Three years ago, most scan data was acquired by time of flight based technology. This was relatively slow. The best scanners could capture a few hundred thousand points per second at best. Sounds like a lot, but not compared to phase based and waveform scanners we have today. We just purchased a new scanner (Leica P20) that captures a million points per second. A single five minute scan can approach 100 million points easily. So, what to do with all that data and how will my poor laptop handle it when I have 50 of those scans??? (Hint: It won’t.) So, while I never used to cull data that I brought into Navisworks for instance, I do cull it now.

Culling can be done a number of ways. I wish there were some more intelligent ways, but for now most culling falls under the headings below:

Noise culling – Getting rid of all those people, cars, birds, dogs, and other moving objects we don’t want to see. This is a manual process most of the time, but it gets rid of totally useless points so it is usually worth it.

Distance culling – This is done automatically to some extent by the scanner hardware as scan data gets to be out of the range within which the machine can return accurate data. You can also automatically apply additional range culling in most processing tools.

Dimensional culling – Want to get rid of any points 10 above the scanner or 5 feet below the scanner? You can do it. Dimensional culling is really useful when you know the data you need is at a certain location and the rest can be dumped.

Sequential culling – This is what most view based and import based culling is really about. It dumps X out of every Y number of points. Navisworks’ default setting is to keep 1 out of every 4 points (culls 3 out of every 4 points). This is a pretty stupid way to cull as it culls equally no matter how dense or how tight the scan data is. However, it’s what we’ve got most of the time.

Density culling – I desperately want this option in the software tools I have. Rather than cull based on point data, I want to cull based on point relationships. If I only need a point every 1 inch, I only want to cull points in areas where the next adjacent points are closer than ½” from the current point. This is much harder and far more resource intensive to do, so most tools do not do it at all. Bummer right?

Property culling – This is also not done by many tools currently available. The idea is that you can discard any points with a reflection intensity within .05 of 1 for instance. This would remove points that might be reflected by safety vests or light sources for instance.

Linking Scans into RevitOnce you’ve wrapped your head around what you want to see, it’s just a matter of getting it in. Revit is actually one of the most difficult programs to import point clouds into. 2013 has improved things quite a bit, but due to the order of the units conversion and instantiation into the model database you have to get it right or delete it. Fortunately, it is only the import you have to redo if you get it wrong – but that can still be frustrating.

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Step 1 - IndexingIf you don’t have an indexed (PCG) file for a scan, you can change the file type in the import scan dialog to look for non-indexed formats. Select one,and you’ll get this popup to the right. You have no options, no settings, justa yes button. Simple as simple can be (too simple probably). Culling has tobe handled before you export to the non-indexed scan file as well.

Step 2 - ImportingImporting the indexed file into Revit you are given a limited number of options all of which are pretty cryptic. Ideally, we would get some ability to preview the results of this mumbo jumbo, as well as the ability to change it later. But for now…

Center to Center – what this really meansis that the centroid of the individual scanwill be placed at the centroid of your model.Why this is even an option has alwaysbaffled me as I cannot think of a singlegood reason to ever use this.

Origin to Origin – the origin (0,0,0) of thescan file will line up with your internalRevit origin. This is a good option if yourscan and you Revit model are set up onthe same local origin point (grid intersection).

By Shared Coordinates – If you have shared coordinated in your Revit model that match the coordinates of your scan data (state plane for instance) then this is your best option (maybe).

Origin to Last Placed – This is useful if you have multiple scan files as it uses the transform from the previous import to set the transform of the current file. So, as long as the individual files (by scan, by level, whatever) are registered to the same coordinate system, you can use this to get import #s 2-X to match import 1.

Step 3 – Checking units and locationThis is where the import process in Revit falls apart fast. You’ve noticed no doubt that you have no options on index or import for scan color or units. You’ve also noticed that the coordinate import options are abstracted into the options above. It gets worse. If a scan is brought in and wasn’t in the units Revit expects (Meters), then you only have oneadjustment option in the type properties of the import. Scaleis what it is called, and it does just that. Anyone used tothis kind of data would assume that if you “scaled” a scanfile that it would be shrunk or expanded based on the originused to import it into the project. However, this is not thecase in Revit! If you scale the import, it shrinks or expandson the import’s centroid. This obviously moves the pointsrelative to their correct origin, making any scan file importedthat isn’t in Meters un-located. Unfortunately, 99% of ourscanning is registered in US Survey Feet on a State Planecoordinate system. This must be intentionally exported to Meters by your scanning crew if you’re going to bring a scan into Revit. Fortunately, Navisworks can handle metric files fine so this doesn’t

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blow up you usage in Navisworks. But, it is extremely frustrating. If you can’t get this from your provider, or your scan data isn’t actually located, you have to go through the process of manually lining up and matching that data to your existing model, or at least to where you want to start modeling.

Step 4 - AdjustingOne area where Revit is easier than Navisworks is adjusting scan data into a location you’re happy with. You can draw lines snapping to points and then measure between them and your orthogonal reference planes or building elements to get rotation. You can do the same with X, Y, and Z and since it is easy to create plans and sections you can easily isolate the direction you want to adjust it and even use snaps to move the point cloud around. Once you’re really close, you can even use the nudge (gasp!) tools to get it to where you’re happy. Remember, neither the real word nor the scan are perfect or even perfectly static, so your job in manually locating a scan is to get critical object(s) as close as possible instead of one location perfect.

Working with Scans to model nativelyNow that you’ve got your scans in the model and in the right place, it is time to start modeling. Generally, working with scans is a two step process. Step 1 is visualization, which for scans means defining what you want to see. Step 2 is modeling. Revit has a very limited tool set in terms of using the scan data to create modeled elements. Fundamentally, you’re tracing. On the up side, there is nothing to really learn for your end users. If they want to make a wall, they click the wall tool. If they want to make a floor, they click the floor tool. Etc…

VisualizationThe point cloud engine in Revit actually does a great job of treating the points JUST like it treats anything else. This is actually a really great thing for end users as it means the same tools they are already familiar with just work. Cut planes, section boxes, and clipping settings in views limit the point cloud naturally. This is one thing Revit’s PCE engine has really right.

SnapsLike I said above, get ready to trace. There are some situations where you’ll find you can snap to the point cloud in Revit using the built in tools, but you aren’t snapping to individual points. Instead you’re snapping to something else that is determined behind the scene that represents some average of the points. It’s actually quite confusing to figure out, but when it works it is pretty good. Usually I turn it off and trace as best I can. Now, I know what you’re thinking… that’s it? Yeah, pretty much. You’ve got a fantastically accurate background to trace off of though!

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Must have plugins for Scan to BIMTo get any more advanced, you’ll need plugins. There are a few out there now, but the two I’m familiar with are CloudWorx for Revit (Leica’s plugin) and Scan to BIM (Imaginit’s plugin). We’re going to take a look at their toolsets as they are representative of most of the tools on the market.

Scan to BIMImaginIt’s plugin works within the PCE that Revit comes with out of the box. Scan to BIM’s toolset is primarily modeling and QA/QC centric. This is the plugin I use most often when working with scans in Revit. There are a number of tools that show a real understanding of how Revit works from both a modeling and viewing standpoint. Kudos to Beau and Matt on this one!

View: Basic view settings.

Clear – clears any visualization settings applied to the point cloud

Manage – opens a dialog to manage point clouds that are loaded and save point cloud load configurations for reuse

Toggle – turns point cloud visibility on or off in the current view

Create: These tools let you create objects in Revit based on the loaded points. So far, these are the best tools I’ve used to create architectural building elements from points.

Wall Region Grow – pick three points in thecloud and this tool will fit a plane to them, findthe edges of the surface, and then give youdata on the fit to make a decision on how tomodel the wall. Create profile wall will createa wall and then edit the profile to match thepoints resulting in a vertical wall regardlessof how vertical the points may be. Create mass wall will create a mass surface toperfectly match the region grow plane andthen apply the wall to the mass face. I lovethis tool. Love love love love love love love

Curtain Wall – this will place a curtianwallinto an existing wall based on two corner points that you select

Arc Wall – similarly, this tool will fit a curve to a window selected set of points and give you some fit metrics to decide if you want to proceed. It will then make a wall for you; although you get no mass wall option so vertical walls only need apply

Reference Point – this places a family in Revit that all the other tools in Revit can snap to, tag, dimension, etc… I know it sounds dumb, but this is actually incredibly useful

Reference Plane – lets you make a reference plane from point selections

Model Lines – lets you make a model line from point selections

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Edge – this will do two region grows on two planar surfaces and then automatically draw the intersection of those to best fit planes in 3D using a model line

Toposurface – lets you select points from a point cloud to create a toposurface. Again, I love this tool.It can save a ton of time on making topos in Revit

Create Level – lets you pick a single point to createa new level in the project, or way cooler you canwindow select a bunch of points and it will analyzeall those points and give you a Z distribution andlet you choose what Z value to set the new levelat. It also lets you control whether views and ceiling plans are created for the level. This one is also super cool

MEP: If you’re in Revit MEP or OneBox, you can use these tools to fit MEP objects to the point cloud. These tools use fitting algorithms to find a best fit for the points selected.

Pipe – window select points to fit a pipe

Conduit – window select points to fit a conduit

Round Duct – window select points to fit a round duct

Rectangular Duct – window select points to fit a rectangular duct

Columns: These tools use fitting algorithms to automatically fit and place columns to the point clouds.

Round – window select points to fit a round column

Rectangular – window select points to fit a rectangular duct

Analyze: As if all the fit data wasn’t cool enough as a QA/QC tool in modeling from a scan, this panel adds measurements, deviation analysis, and interference checking to the menu.

Measure – lets you make all kinds of measurements from the points, from cylindrical to planar to plain old point to point and point location

Deviation – this is the killer tool for me. Once objects aremodeled, you can pick any object and run a deviationanalysis to see how closely the object matches the pointcloud. The wall to the right is not a good fit (manuallytraced intentionally wrong). We can see that the rightside of the wall is getting out of an acceptable tolerancerange (above ½” off). On a side note, this gives us apoor man’s workaround to getting X, Y, or Z rangemapped colors. It does it relative to a face, but if youmake a big transparent floor and run this analysis, youget the same thing.

Interference – again, a really nice tool. Interferencechecking is rarely done in Revit, but this tool helps youintelligently check the point cloud against new objects whichcan save you a lot of time by making it so you don’t have to modeleverything just to coordinate against it

Survey: The survey tools let you create survey points that can then be moved back and forth between the Revit model and total stations for layout or verification. They can also be helpful

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to locate a scan in Revit if you are having trouble with it. You can import points, create points, or export points. These aren’t directly related to scanning so we won’t cover them.

Modify:

Adjust Slab – allows you to adjust a slab to match deviation points from that slab’s face. It requires you run a deviation analysis first. Still, this is very useful

Align to Point – this seems like a great tool, except it aligns normal to the face of the geometry picked and doesn’t align it to a region grow planar fit of the point cloud, but to an individual point. In the case of our wall above, it will move the wall normal to its face so that the face is coplanar with the selected single point, but it won’t actually align it to the points. Thus, the rotation of the wall isn’t fixed

Tools: Really, this should be called views. These tools help you quickly create views in Revit that are aligned to what you’re trying to work on. These tools are somewhat less necessary with the advent of the workplane viewer, but can still be nice as shortcuts.

Create Sections – creates a bunch (set number) of section views through the point cloud. This is pretty nice as a quick way to set up a bunch of QA/QC views

Work View – this creates (or updates) a 3D view with a section box based on a window you draw in a 2D view. This one is really helpful for quickly creating a working view to model in that limits the point cloud and model to the area you’re working in. I want to add this button to my view tab

Set Workplane – lets you set a workplane based on selecting three points from the point cloud. Personally, I’d rather it set the workplane of a region grow from those three points, but still this is very handy modeling intricate details on historic preservation projects

Work on Wall – quickly creates a section view aligned to the interior or exterior face of a wall in case you need to edit the profile further, etc… this is more helpful than you’d think at first considering that an accurate model from a scan has tons of elements that are ever so slightly off axis

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CloudWorx for RevitLeica’s toolset for Revit is primarily focused on improving the way in which you view and interact with point clouds. For starters, Leica rips out the guts of how Revit imports and displays points and replaces them with their own point cloud engine. This changes how you import/color/and limit point display and makes it more like traditional point cloud tools like Cyclone (Leica’s stand-alone application). This may be a good or bad thing for you and your users because most of the traditional applications are nor very Revit-like. So, some of the tools like fences or bounding do not behave the way a trained Revit user will expect them to. Still, it brings a comprehensive set of tools that are worth looking at. One big thing to note is that CloudWorx uses the IMP format instead of PTX/PTS so you

will want the whole project database and not just an exported file if you’re going to use this tool.

Project: This drop-down gives you all your import/export related options.Remember, since CloudWorx completely replaces the PCE in Revit youbring in files completely differently. We’re not going to do a CloudWorx training in this class, but I do want to go over some of the important

advantages with y’all. Import MS View – imports a database into a project

Open/Close project – open or close a project

Save/Save As project – saves all the project settings (clipping, etc…)

Configure Database – lets you configure database settings

Scan World Explorer – opens the cyclone tree view

Load Max Setting – what it says

Levels: This panel lets you create levels.

User lets you set levels as being user defined (like normal)

Point lets you create a new level by selecting a point (Nice!)

Clipping: This is really important in CloudWorx because it will only display a set number (like 40MM) of points. So, to increase the density of points in the area you’re working you have to clip out (hide) the points in the areas you don’t need at the moment. This is also where CloudWorx gets un-Revity. Rather than using the view settings to clip a point cloud (like a section box or view clipping), CloudWorx behaves a lot more like Cyclone. If you work with Cyclone this is a good thing. If you’re a Revit user this is not a good thing.

Clipping Manager – since clipping planes can be saved as part of the project, the manager allows you to name and manage the clipping settings you create so they can be reapplied later

Box Fence – draw a rectangular fence in a view and clip out any point outside of it. If you’re in a 3D view then, you guessed it, you drew a 2D clipping box in a 3D view. Freaky

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Limit Box – lets you create a 3D box to limit the point data based on various input methods

Sectioning (X, Y, or Z) – lets you define a range of points in the X, Y, or Z axis to display. Using this in a plan is the closes you can get to matching what Revit does out of the box in a plan view

Forward/Backward – moves the section plane that is limiting the points in the current view forward or backward (normal to the view). Again, in 3D views this can create some weird results

Reset Clip – Self explanatory

View Right – “Rights” the view

Fitters: Leica does have a pipe fitting toolset in CloudWorx, although it seems to be way behind what is present in Cyclone.

Pipe – Works pretty well

Connect Pipe – Works ok at best

Flange – Works ok at best

Section – Haven’t been able to get any use out of this tool

Rendering: This is all about how the points are displayed in Revit.

Regenerate – Regenerates the points after changing settings

Point Visibility – Toggles points on or off

Point Density – Lets you set point density options, though not as intelligently as I’d like to see

Point Coloration Options – Hallelujah! This is the biggest win in CloudWorx for me. As someone who has worked with a lot of scans in a lot of software, I’ve learned that point coloration is one of the most important tools to help end users understand what they’re seeing and make the right decisions. Since CloudWorx is based on Cyclone, those advanced options like X, Y, or Z range color mapping are all there in addition to the basic ones we all expect (but don’t get in Revit without CloudWorx).

Information: Location at Pick, Location of Cloud, etc… These tools are useful for setting up coordinate systems in Revit, and the angle to true north can be manually figured out by measuring multiple locations.

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To BIM or not to BIMThe long and short of it is that you don’t always need a BIM. Begin with the end in mind is always a good mantra, and that is no different with Scan to BIM workflows. Ask yourself WHY you want to model something you’ve scanned. What is your use case, and can the scan data serve that purpose as is?

Use Cases Analysis – You need to model it

Demolition – You need to model it

Documentation – You need to model it

As built verification – No need to model

Coordination – No need to model

Etc…

Scans in a coordination environmentSo, we mentioned coordination and that usually means Navisworks. Scans are fantastic for coordination work. Whether you’re trying to as-built existing conditions or something you’ve built, scans can provide a lot of value for very little money. Navisworks is much better about working with scans than Revit is currently, but there are still a few quirks…

Loading Scans into NavisworksLoading scans into Navisworks is relatively easy. There are some global Navisworks settings to pay attention to however. Like Revit, Navisworks indexes the scan files. Navisworks creates NWC files of course, but these files have only the information Navisworks is told to extract from the scan file.

Coordinates and Units – Like with Revit, coordinates are where everything starts. Navisworks is not picky like Revit is about being near the origin. Typically, we request that all our scans are provided to us registered in state plane coordinates. This is useful because all our sub models and all our Revit models are set with state plane coordinates as well (in Revit this is done with shared coordinates of course!) So, everything *should* just line up! It doesn’t always happen, but it usually does. If you can get a scan delivered to you in a “located” format, you should take advantage of it. If your scan just comes in any which way, you’re going to have to manually align it to your model which is time consuming and no fun. Navisworks also handles units correctly, changing the units scales the scan around the origin of the scan, not the centroid. So, you can correctly set the units after import no matter what they are. I prefer Metric for scans into Navisworks because there is no potential confusion between Survey Feet vs. Imperial Feet.

Coloring – Like Revit, Navisworks’ indexed files only have one color option. Unlike Revit, you can pick for it to be created with a lot of traditional coloration options. Typically, I like to create multiple indexed (NWC) files for each scan file. I’ll usually create one with intensity coloring, one that is grayscale, and one that is photo colored if photos were taken.

Culling – In the past, I always brought scans in 1 to 1 in Navisworks because it handled them so well. So, no culling needed! However, with phase and waveform scanner data, this is no longer realistic. Even a small set of scans at those densities can bring even Navisworks to its knees. However, for certain tasks you may still need that peak density. What to do? Just like

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with the coloring, you can create multiple indexed files. I usually create one at 1:1, one at 1:4, and if it is a really ginormous scan one at 1:10.

Loading – Once you’ve created all your NWC files, I like to open the project I’m loading them into (it has the Z axis set correctly, etc…) and then append one of the scans in to it. This is troubleshooting time! If your scans come in and match you model, then pass go and move to the last step. If not… How much are you off. If you’re off by a couple of inches, you might have a survey bust – call your scanner and your field crew and work it out. If you’re off by several feet (or a few hundred feet) it might still be a survey bust, but it might be unit related. What unit format was the scan exported in? Survey feet and imperial feet are actually slightly different so a project 6 million feet away from the origin can be busted by even a fractional difference in the units. Metric is as metric does, which is why it is a safe unit for scans (that, and all scanners are metric internally so why not stick with it unless you have to be different?). If you can’t find a resolution, you’ll just have to suck it up and manually locate the scan, just like you would if you had a non-located scan. (This isn’t the end of the world, just a PITA.)

Aligning – If you’re going to have to move your scan manually into position, there are a few very useful tips.

A scan isn’t perfect and neither is reality, so don’t plan on matching it up perfectly. Use the “law” of averages to your advantage. (Everything will be close, but nothing will be perfect)

It’s all about moving things at varying orders of magnitude. In other words, don’t fret about 256ths of an inch when you’re a thousand feet off. Get it close, then get it closer, then get it closer, until you’re comfortable with it.

Get the rotation right first. If your project is orthogonal in the model, then you can cheat and try lining up the longest straight element in the scan with the edge of the Navis Window (that’s a tip? Yeah, really, it is.) If it isn’t orthogonal, then your best bet is to move your scan close to your modeled elements and then do your best to get them close to a match. After you check one element, check the next longest, and then the next longest. The longer a straight element is the easier it is to get it eyeballed into the right place. I highly encourage using Navisworks’ measurement tools to help you in this process, but with the fuzziness of a point cloud and the preciseness of the virtual model sometimes the measurements can be too much of a good thing if you don’t visually check alignment. Ultimately, you repeat this process until you’re comfortable with the rotation being correct enough for the end use in question.

Get the location right. The measurement tools are much more helpful here, as is a foot/inch calculator. After I nail the rotation, I usually re-set the X, Y, and Z offsets to 0. Then, I find a corollary point in the model and in the scan, and use the measure tool to measure from the point cloud point to the model point. Then, you can pretty much type those values into the file transform menu and apply it. This will get you pretty close pretty fast. Then, you just need to check multiple areas where the scan features and the model features are recognizably the same and – again – get them all close. I prefer to do this one axis at a time, and I always start with Z. This is where the foot/inch calculator is handy. You’ll be adding and subtracting 32nds and 64ths of an inch and your head may explode without it.

Write it down. Once I’ve gotten the location right, I always screen shot the File Units and Transform window in Navisworks for that scan and save it in the job folder. If you’ve made multiple NWC files from a single scan file, these same offsets will work

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for the rest. Plus, it’s good to have if some goof ball goes into your Navisworks directory and deletes your scan files “because they are big.”

Saving – Historically, NWC files from scan data have been a little unstable in NWFs. I’ve had them flip, rotate, and even scale on me when I leave them as NWC files. As a result, I like to delete the model from the NWF I loaded the scan file into to confirm the location and orientation of the scan. This leaves nothing but the located scan data. Then, I save it as an NWD. Since this is located fixed data after the save, I’ve never had issues with it moving on me (short of user error).

I have not tested 2013 to see if this is resolved since the only way I know how to test is to let it screw me up on a project. So, better safe than sorry.

Scans as a coordination toolOnce you’ve got you scans in the right place, now you want to coordinate, right? Fortunately, that’s a pretty easy thing to do. The tools Navisworks has will work with laser scans without any tricks.

The Walk Through – My preferred method of coordination (and not just for laser scans) is the scripted walk through. I find that scan data set to color by intensity stands out like a sore thumb when it is in conflict with other modeled objects. It is pretty easy to spot. I use this method for 90% of my coordination process anyway, so applying it to scans just makes sense to me. That said, you never catch everything this way…

Collision Detection – So, we typically use Navisworks’ clash detective for cleanup duties. If you use it for all your coordination, rest assured it will work for point clouds too as long as they are dense enough. Since the clash detective relies on geometry intersection, you are counting on your geometry coinciding with a point or the soft clash area around the point and the pipe. Because you can set that soft clash zone, this works on all but the sparsest point cloud data. There are only two downsides to clashing a point cloud in Navisworks. First, the point cloud is treated as one object per scan. You can’t pick individual points. Likewise, the clash detective has the same limitations. So, you get a lot of clashes linked to a single scan and the whole scan turns red. You’ll need to have command of Navisworks’ clash visualization filters to make this useful information. The only other comment worth noting is that noisy scan data can introduce a lot of false positives into the clash detection process whereas your eyes are pretty good at ignoring that single stripe of a superintendent with the giant beer gut that the scanner recorded as he walked by.

Scans as a verification toolUsing scans in Navisworks as a verification tool is also pretty easy, although a little inverted.

The Walk Through – Not surprisingly, I also like to walk through a model to look for verification. Again, it is pretty easy to see if there is an object with no correlated scan data or if there is scan data with no correlated object. However, if you really want to get automated, you can also use the clash detective for this as well…

Collision Detection – Using the clash detective to do verification is like coordination turned on its head. Instead of looking for clashes, you’re looking for no clashes. That’s right, any objects that don’t have a clash also don’t have correlated points or are so far from their correlated points as to not register a clash. So, anything in the model that doesn’t clash with a point cloud is a potential problem. Again, noisy scan data can give you false clashes – which in this case is a bigger problem because you aren’t even looking at the clashes. So, don’t use this method if you’ve got noisy scans.

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