3 d laser scanning

1. Laser Scanning for Building Information Modelling: -
Laser scanning has been used in geospatial and survey fields for a long time now, and with the advent of
BIM, the potential for using laser scanning in construction industry is a new trend.
How is Laser Scanning done?
- Scanners used to send laser beams for making positional measurements
- These beam touch the surface of the object and are reflected back. The reflected beam is used
to measure the distance of the object from the scanner either by phase shift method or by time
of flight method
- Different scanners are positioned at different locations and a large dataset is obtained from
them. This dataset is then combined together to form a point-cloud which represents the
scanned object
- Point-cloud data is then fed into BIM modeling softwares and BIM object-models are drawn by
referencing to them
- Some softwares like Trimble RealWorks can run algorithms on these point cloud and recognize
the object and create the model, but still manual work has to done to make an accurate model
- Scanning can be time consuming task and thus it should be well planned
o What to capture and Level of details to be captured – resolution and quality settings of
the scanner are defined by it
o To calibrate different scanners together and also to increase the accurate of a scanner
different common targets are set throughout the area to be scanned
3D Modeling using point-clouds
- Authoring softwares like Tekla, Revit (for detailed and complex structures), Sketchup (for less
detailed structures) can be used to convert point-cloud datasets to 3D model
- External authoring application requires a methodical approach to model creation – more
important elements created first followed by less important ones
- Models obtained from these point clouds can be used in a variety of ways – can be used to get
as-built information of site and then use this as-built data to introduce new elements which are
in congruence with the existing one
- Decision for prefabrication can also be facilitated as laser scanning provides accurate data in
reference to where the prefabricated structure will be installed

2. - Code requirements can also be checked and complied
4D Scheduling
- Detailed location based schedules can be created – location base schedules are more
advantages than traditional schedules as the take advantage of the location information along
with quantity information – congestion, workspace constraints etc. are visible in location based
scheduling
- Particularly helpful in renovation project – contingencies that may arise are known and time
buffer can be put accordingly
5D Quantity and Cost Estimation
- 3D model obtained from point cloud can be further used for quantity and cost estimation
- Different types of work require different crews – contingencies for time can be speculated by
using such models which can further be used to calculate the cost implication on the project
- As such quantity and cost estimating can be done more accurately, and thus estimated time of
completion and project cost can be known more accurately
- Cost buffers can be put in project bid price to account for contingencies – making contractor less
likely to incur loss
6D Facilities Model
- As-built model representing accurate site condition can be formed
- As-built can be checked with designed BIM model to check for consistency during handover
after construction
- All this can be done in office setting thus is more safe and time saving
- Even if site visit is required for further investigation – the team knows the physical space and
constraints as they have the as-built model and can plan a safe approach for inspection and
maintenance
- It also facilitates proactive approach to facility management
- Management and repair of historical structures also benefit from 3D laser scanning as accurate
as-built data is available which can be used to plan the renovation and restoration activities
before things get out of hand

3. Thus, laser scanning adds a new value to BIM workflow which has numerous applications and projects
can benefit in cost, time, quality and safety.
3D Laser Scanning – As-Built Reality Capture for BIM
LiDAR a detection system that works on the principle of radar (pulsed electromagnetic waves), but uses
light from a laser. 3D laser scanning captures three dimensional information reflected from the surface
of and object and received by a laser sensor and converts it into a point cloud by the process called
registration.
- BIM and CAD models are ideal representation of a structure, while structure formed by point
clouds using laser scanning are accurate representation of as-built condition
- Scanning is easy, but converting it into BIM/CAD is a challenge
- Once exported to BIM/CAD – 2D site layouts, plans etc. can be extracted readily
Laser Scanning and BIM
- GIS, remote sensing, stereo photogrammetry and LiDAR are overlapping and competing
technologies and BIM has the potential to unify them and use them together for good
- Documenting as-built conditions has always been a very time consuming task and is often prone
to inaccuracies
o LiDAR provides a fast and accurate solution
o It is expensive, but cost is overshadowed by the speed, quality and quantity of visual
information that is produced by it
o Huge datasets are produced and require a lot of processing capacity for a computer to
handle this data
- Various softwares are there in the market currently and further more are been developed.
- There is huge potential for implementation for Laser Scanning in construction industry and all
phases of construction from predesign to construction to facility operation and maintenance
- E57 format by ASTM which is an open source platform is seen as a potential format and
standard for improving import and exchange of 3D scan data to BIM
- Scanning data and BIM are best when combined together to document as-built condition of a
building or structure. A uniform platform to make them compatible is the missing link

4. Future
- Object recognition and extraction from point cloud will remove the need for modeling
everything
- Automating modelling process by converting point cloud to BIM models
- Using technologies like GIS and combining it with point clouds from laser scanning and building
models from them
- Creating sections, plan, layouts etc. directly from point clouds
- Using it for Terrain modeling and 360 panoramic photography