Frequently Asked Questions
BIM & Scan AutoCorr™ is designed for use by design, engineering, and surveying professionals who are familiar with basic file management and BIM design and review applications. In order to provide as much assistance as possible, we do our best below to provide up to date Frequently Asked Questions (FAQs). As we obtain more feedback from yourself and other users we will update the FAQ knowledge base. 
Thank you from the BIM & Scan team


1.    How long does (should) BIM & Scan AutoCorr™ take to run my files?

Depending on the size and complexity of the file, the running time differs, e.g. the Conference room test files take about 1.5 mins (IFC = ~ 1.5 MB and E57 = 2.1 GB), while the Plant Room Test Files take about 7 mins (IFC = ~ 44 MB and E57 = 4.5 GB). In short, there is no definite answer here because of many variables that come into play. The complexity of the model, density of the original scan data, and the amount of scan positions/poses highly affect the run time. This is why we have also recommended best practices in relation to planning and scanning on the Getting Started page: Scan Planning / Processing / Registration Checking.


2.    Does running BIM & Scan AutoCorr™ at different Tolerance’s affect the time it takes to process the Output File?

Running the same files, of the same size and complexity, at different tolerances does NOT affect the processing time of the Output File.

 

3.    My point cloud is greater than 8GB. Can I run BIM & Scan AutoCorr™?

No. If you would like to to cluster your data in larger groups and run files larger than 8 GB, then please contact us at https://bimandscan.com/contact to speak about our Enterprise Subscription available package features.

4.    What do I do if I get a process run FAIL?

Check the size of your point cloud and see question 3 above  and check your geometry and see question 5 below and the Getting Started page document under Modelling: Geometry Requirements and Modelling Guide Capping Holes.

It could be the geometry of the model is not modelled properly, i.e. has single faces, holes, conflicting geometry/faces. Flipped faces, etc. This occurs most when using third party BIM objects in your Native BIM Authoring tools. Best practice is to always use the authoring tool you create your IFC CV2.0 to create your model objects.

 

5.    How do I check if I have a properly formed IFC2x3 CV2.0 Coordination File?

a. First make sure you exported from you authoring tool using the IFC2x3 CV2.0 Model View Definition (MVD). See videos on the Getting Started paged: 4d Re-Run for an example using Revit® on a PC and 5d Re-Run for an example using ArchiCAD® on a Mac OS. In this regard, you can also open your IFC2x3 CV2.0 Coordination File in Note Pad or other text editor and check the file header; It should say something similar to:

ISO-10303-21;

HEADER;FILE_DESCRIPTION(('ViewDefinition [CoordinationView_V2.0]

And, you need to check the schema version so look for:

FILE_SCHEMA(('IFC2X3'));

ENDSEC;

Or, in the file code, similar to:

#13= IFCAPPLICATION(#12,'20.0.0','ARCHICAD-64','IFC2x3 add-on version: 3012 UKI FULL');

b. A second way to check it is simply run it through BIM & Scan AutoCorr™ with its corresponding E57 file, and if the run is successful, then the IFC2x3 CV2.0 Coordination File is good for this purpose.
c. The third thing to do is, as in FAQ 4 above, see the Getting Started page document under Modelling: Geometry Requirements and Modelling Guide Capping Holes.


6.    Why do some points appear to be incorrectly associated?

Please see the Getting Started page document under Modelling: False Positive and False Negative.


7.    Do red points in my BIM & Scan AutoCorr™ Output File mean more than one thing?

Yes. Red points can be objects on the construction site that were not in the model, e.g. temporary construction materials, people on site, cars, etc., hence the second meaning, objects that are out of tolerance and/or out of position, i.e. the object on the construction site could be on the model, but in a different location.

 

8.    What do the colours mean in the BIM & Scan AutoCorr™ Output File?

The colours are the IFC Entity Type classification of the object using the IFC 2X3 Schema. We have randomly given different colours to every IFC Class. These Random colours stay consistent in every run of BIM & Scan AutoCorr™.

 

9.    Why does my BIM & Scan AutoCorr™ Output File E57 Point Cloud have less points in the dataset than my original Point Cloud Input File?

BIM & Scan AutoCorr™ Subsamples the data set. The subsampling margin of error is < the possible input for Tolerance, i.e. subsampling < 5mm. Note this subsampling can be adjusted for clients under the scope of our available Enterprise Package, or under another type of agreement.

 

10.  How do I check if my input IFC and E57 are properly registered to each other?

Please see the Getting Started page document under Scanning: Scan Planning / Processing / Registration Checking.


11.  What effect will occlusions have on BIM & Scan AutoCorr™ results?

The IFC model can contain Entities that do not exist or are in a wildly different location versus the scan data, this means that the analysis performed by BIM & Scan AutoCorr™ cannot see past objects occluding or blocking visibility from scan positions/poses. When this occurs, the points are coloured red as non-corresponding, as the occluding object is found first and is detected as out-of-tolerance. To reduce the impact of occlusions, ensure your scan positions are well-spaced out and can properly cover all required parts of the built environment from several angles. Occlusions in the point cloud, i.e. objects occluding when it was scanned, will simply leave data points in the wrong areas, and those will be highlighted correctly as red (non-corresponding) if the space in the model is empty.

 

12.  Does BIM & Scan AutoCorr™ only work for Buildings?

No. We have tested BIM & Scan AutoCorr™ on several different types of projects including Infrastructure, e.g. Tunnels in Spain. For more information please read the whitepaper.

 

13.  How much quicker is BIM & Scan AutoCorr™ compared to traditional manual methods?

In tests on projects that we have conducted with partner design companies, we have found 6 hour manual comparison and overlay tasks – to find differences or errors in models or construction – being reduced to 15 minutes. That is a time saving of 95%.

As importantly as time saving BIM & Scan AutoCorr™ gives an objective and complete result set that is not reliant on the alertness of the individual comparing raw model and scan data by eye. BIM & Scan AutoCorr™ provides 100% accountability unlike manual methods which do not afford such measurement at all.