One of Gene Roe’s recent "In the Scan" blog comments really hit home. He proposed the concept of GeoBIM – using BIM (Building Information Modeling) methodology to manage civil infrastructure projects. I totally agree, but would like to add one additional thought. Instead of transposing the term "building" to areas outside of structural walls, I propose that we adopt a new acronym "SIM" – Site Information Management.
Today, BIM is a very common buzzword in architecture and among contractors who specialize in building construction. Checking out the definition on WIKIPEDIA (http://en.wikipedia.org/wiki/Building_Information_Modeling), it turns out to be a pretty hefty concept. There are two key facets of BIM that make it different from the traditional civil engineering workflow we use for infrastructure projects today:
- Managing the same data throughout the project lifecycle.
- Representing a design as 3D objects with geographic information, geometry, relations, and attributes.
Let’s use a typical road construction project as an example to understand the differences SIM can make. In civil engineering today, we design mostly in 2D. Features such as pavement limits, storm drainage pipe, sewer lines, and guard rails are represented by 2D lines with descriptive annotative text. To understand the inter-relationship between these components and avoid conflicts, we resort to cross sections at set distance intervals.
Two-dimensional paper plans are generated for the bidding, construction, and inspection phases of the project. As-builts drawings are created on the original paper plans. After construction, the owner receives reams of paper plans and record documents for managing the facility. If the owner uses a GIS database for asset management, all the features must be remapped and pertinent attributes recorded.
In SIM, 3D digital data is used from start to finish. Base terrain and existing feature data are acquired as LiDAR point clouds. New features are designed and specified in 3D. Take guardrail as an example. One section of guardrail is created as a 3D object. All pertinent information such as material specifications, manufacturer, and cost are attached to the object as attributes. In design, model sections are joined together and attached to other 3D models of posts and end-sections, forming a complete guardrail installation. In SIM, the inter-relationships between the guardrail section, posts, and end-sections are also defined in each component.
At any time, the entire roadway project can be viewed in 3D from any perspective. During the design phase, we can easily visualize potential conflicts between components, above and below ground. Cost estimates and materials orders are easily derived through computer software operations. Date of installation and as-built geospatial location are added as attributes to the 3D objects as a product of periodic construction inspections. The owner receives a complete digital 3D record of installed features and attributes that can be used for asset management in a geospatial environment during the post-construction phase of the life cycle.
How and where do mobile mapping systems fit into the SIM concept? Actually, the fit is perfect. Topcon’s IP-S2 and HD Mapper systems collect 3D data in the form of colorized LiDAR point clouds and 360 spherical images. Topcon’s software enables users to manage and format the data. Here are a few examples where a complete mobile mapping solution can be used for the SIM workflow:
- Planning surveys
Mobile mapping systems are perfect for making a route survey to study a corridor prior to new construction or improvements. In the case of a road-widening project, we can map existing assets to be removed, relocated, or replaced. We can study the impact our plans have on adjacent properties and discover potential impediments to construction.
- Base maps for design drawings
Colorized LIDAR point clouds can be imported to 3D CAD software as base maps for design. Specialized LiDAR management software can be used to clean-up and organize the point cloud data prior to design stage. Topcon’s ScanMaster has tools to eliminate non-essential points and reduce the data to exactly what is needed. The region select tool will isolate ground surface points under specified parameters from points of higher elevation, enabling the extraction of bare earth or finished surfaces.
- Construction inspections
Periodic drives through a project under construction give us near-instantaneous updates on progress. Percent completion and contractor’s compliance with requirements such as traffic and erosion control devices can be determined by viewing the images. Installed object quantities can be mapped and calculated to verify pay estimates. Using point cloud data, we can generate surfaces to verify grades and calculate earthwork or finished surface volumes.
Collecting as-built information as construction progresses during mobile mapping inspections is a real time and labor saver. For example, Topcon’s Spatial Factory software enables viewing 360 images registered to the point cloud. We can import component shapefiles with attributes created in the design phase, identify them visually, map their in-place geospatial positions, and add installation date and other attribute information. After mapping is completed, we can then export out to our SIM project database.
- Asset management
In the post-construction phase, the owner or facility manager can continue to monitor the condition of assets with a mobile mapping system. Maintenance tasks can be identified from periodic drive-by surveys. Recording changes over time and comparing them can also disclose destructive trends that can lead to failure. Good examples are monitoring surface erosion around a pipe headwall or changes in finished surface grades that may be caused by subgrade problems.
If you would like to see good examples of how LiDAR and mobile mapping systems can be used for SIM, check out Autodesk’s On-Demand webcast: "Improving Road and Highway Design Workflows": http://usa.autodesk.com/adsk/servlet/oc/index?siteID=123112&id=12426664
Another interesting presentation from the Scandinavian company ViaNova has good graphic examples of "BIM on the road" and outlines the benefits. The presentation can be downloaded at: http://tuta.oulu.fi/LCI%20Haugbotn.pdf
SIM is already a reality. The hardware and software tools are available. What we need now are more people to adopt and implement this methodology for improved management of civil infrastructure projects.
(Note – Mobile mapping vehicle photo courtesy of Rapid Survey Solutions)