At SPAR 2013 Keith Warren, BIM/3D SUE Manager at VTN Consulting gave a fascinating presentation on the 3D above and below ground model of city infrastructure including roads, utilities, telecom, and buildings that VTN has developed with the City of Las Vegas. Keith believes that at the present time Las Vegas' 3D city infrastructure model is unique in North America.
This model also represents a classic example of the benefits of convergence, the integration of engineering design data including building information models (BIM), geospatial data including digital terrain models, high resolution photogrammetry, and point clouds derived from laser scanning, together with 3D visualization technology.
About five years ago the City of Las Vegas approached VTN because they saw some potential value in 3D modeling. At that time the city had had little experience with 3D modeling. VTN has a broad range of in-house capabilities spannng engineering (traffic, public works, and 3D subsurface utility engineering), survey including laser scanning, GIS, building information modeling, and visualization. Over the next two years VTN focused on education, working with the city and other utility agencies to introduce them to 3D modeling and visualization technology. VTN organized workshops with the city, local utiltiies including the water district, and other public agencies to educate them in some of the capabilities of the new technology. At the same time they worked with the city and other public agencies to understand the problems they were facing.
Challenge: subsurface utility engineering (SUE)
One of the problems that was identified repeatedly in these workshops, not only at the City but also at the utilities, was hitting underground infrastructure during excavations. According to national statistics, in the United States an underground utility line is hit on average every 60 seconds. The total cost to the national economy is estimated to be in the billions of dollars. The problems is that in most municipalities in North America, for years underground utility lines have been put in the ground not according to plan but wherever it has been easiest and cheapest to build them. In addition 2D as-builts of underground infrastructure are unreliable. The result is that in most municipalities the location of underground utiltiies is very poorly known. This was the situation in Las Vegas.
Since the city had been educated on 3D modeling technology by VTN, they decided that this technology could provide a solution for the problem of locating underground utilities. The City decided to go ahead with a project to model one and half miles of Main Street in the older part of Las Vegas. The project was intended to model below and above ground facilities including roadways, utilities and telecommunications, and buildings.
The project also specified implementation of a new low distortion geospatial coordinate system to make it possible to support engineering grade accuracy for geolocating infrastructure.
Buildings were modeled in several ways, including extruding a building footprint from a GIS, using building models from the Sketchup 3D Warehouse, laser scanning existing structures, and complete BIM models for newer buildings provided by architects.
A variety of techniques were used for reality capture of underground utilities and other infrastucture includng GIS, survey, design records, test holes, and ground penetrating radar (GPR). Above ground utilities were captured by combining GIS data with mobile laser scanning.
In the future to improve data quality for underground infrastructure, since the City owns most of the right of ways within Las Vegas proper (some is owned by the Nevada DOT), it has mandated that in the future contractors are required to use open trenching for utiities and all work has to be surveyed before the trench is closed.
Intelligent city infrastructure model
The deliverable was a set of 3D models of all the underground and aboveground infrastructure and buildings for the one and a half mile corridor of Main Street in old Las Vegas. Engineering design and other data was combined with the City's geoimagery, digital terrain models and other GIS data. The models were designed to run with the software that Las Vegas already had including Civil 3D, Navisworks, ESRI ArcGIS and Autodesk Infrastructure Modeler (Infraworks).
Map-21 and Every Day Counts
Map-21 and Every Day Counts are Federal Highway Authority (FHWA) initiatives that are designed to encourage the adoption of 3D modeling. MAP-21 (Moving ahead for progress in the 21st Century) requires 3D modeling and virtual construction and visualization technology for all eligible projects. The Federal government will provide matching funding on projects using intelligent 3D modeling and visualization of up to 5% fo project costs. The Map-21 initiative was announced last July, but it turns out that what Las Vegas has done is in Keith's estimation 80-90% compliant with Map-21 guidelines.
Every Day Counts is another FHWA initiative that encourages 3D modeling. According to the FHWA 3D modeling in transportation construction allows for faster, more accurate and more efficient planning and construction. The FHWA foresees that as the benefits are more widely recognized, many in the U.S. highway industry will transition to 3D modeling over the traditional two-dimensional (2D) design process.
Benefits of the intelligent 3D city infrastructure model
One of the major benefits that Las Vegas has experienced as a result of developing the intelligent 3D city infrastructure model is increased safety because of the reduced risk of unexpectedly hitting underground utilities especially hazardous ones like gas mains.
The benefits of being able to accurately locate existing underground infrastructure are immense. They include automated clash detection to identify potential problems when plannng, designing and constructing new undergound infrastructure. Also there are reduced operating costs because of reduced truck rolls for cable/pipe locate operations.
Overall the City has found that the 3D model approach provides more information per dollar invested, in other words more capabilities at lower cost.