- SPECIAL REPORTS
- THE MAGAZINE
Santa Monica Boulevard isn’t an ordinary street. Featured in countless movies and television shows, it is a popular tourist destination that leads to Beverly Gardens Park, the Wilshire Fountain, City Hall and the future Annenberg Center of Performing Arts. The boulevard is one of the main thoroughfares through Beverly Hills, Calif., the city with one of the most famous zip codes. Approximately 51,000 vehicles drive down this famous corridor each day.
In 2010, the City of Beverly Hills identified Santa Monica Boulevard North, the 1.8-mile arterial thoroughfare that bisects the city, to be in critical need of rehabilitation. The city issued a request for proposals for a topographic survey to detail the current road conditions and resolve right-of-way issues. The survey would also involve research, identification and plotting of existing utilities to provide an accurate as-built of all facilities within the 85-foot-wide right-of-way of the boulevard.
A key component of the project was determining how to work around the significant traffic volumes; the survey would need to be performed safely and with a high level of detail--without disrupting traffic. Typical traffic mitigation efforts, such as limiting traffic patterns or shutting down streets, were not an option due to the importance of this principal arterial road. After evaluating the proposals, the city contracted with Rick Engineering Co. (Rick), whose approach involved using multiple methods to meet the survey specifications.
The city hired Rick in November 2010 with the understanding that the entire project must be completed within an abbreviated time schedule of only three months. With the schedule shortened even further due to the winter holiday season, the Rick team faced a substantial hurdle.
The 3D point clouds created by laser scanning are virtual site models where planimetrics, breaklines and spot elevations are identified in the safety of the office environment to create accurate final design level topographic maps. All visible site features, including buildings, landscape features, utilities and other site improvements, are compiled from the point cloud detailing feature characteristics. The resulting 3D point cloud is transformed into a CAD model of versatile and measurable objects that can be tested in order to verify the new design with the existing conditions. It was an attractive proposition for the city managers.
With the city’s approval of this innovative technique, Rick surveyors were able to move forward. However, laser scanning wasn’t the only tool used by the firm. Rather, Rick decided to use a three-prong method: Survey it on the ground, survey it from the air, and survey it without touching it. This multifaceted and integrated approach to collecting, compiling and processing road conditions provided a nonstop fast track to develop the final usable topographic map the city needed.
For the second approach, Rick photogrammetry staff planned and executed an aerial photogrammetry mission that captured high-resolution color stereo imagery across the entire project. To minimize the visual impact of the survey on the community, the aerial targets were established by using photo identification points instead of typical painted aerial targets. The data was then compiled into 1-foot contour mapping, while planimetrics were extracted for a 400-foot-wide corridor of the defined project limits. A high-resolution (0.25 foot) color aerial orthophotograph of the overall project was created from the color photography and provided as an early deliverable planning tool to the city.
Laser scanning took the lead role in the third and final approach. Because the volume of data collected during one laser scan is exponentially greater and collected in less time compared to a traditional field survey, the crew’s work efficiency was increased considerably.
Surveyors used a Leica ScanStation 2 laser scanner to capture a dense point cloud of data for roadway and parkway details, including high-resolution 360-degree color photography at each scan location, without closing traffic lanes. The surveyors used the dense point cloud to locate all topographic features in the traveled path. All details were collected from the safety of sidewalks, medians and pop-outs, keeping the field surveyors out of the street and well out of the range of the constant heavy traffic.
Within three weeks, the survey crew had the necessary data in hand. Staff then compiled engineering design level 0.5-foot contour mapping, planimetrics and surface utilities from the collected point cloud data. The accuracy of the laser scans provided a high amount of confidence in producing final design level as-builts for all of the existing surface features within the right-of-way. As an example, all points that define the top of street curbs were compiled from the scans. This provided greater detail than collecting 25-foot cross-sections. The laser scans filled in accurate data all along the roadway corridor, minimizing human interpretation of critical changes in geometry that might impact future design work.
The team also had to convey the inherent accuracy and expected detail of each deliverable to the client while minimizing the complexity of the deliverables. After considering multiple CAD files and different layering schemes, the team ultimately decided to provide delineated zones in a single composite CAD file along with notes on the cover sheet of each map. Each zone was labeled with the aerial mapping accuracy (photogrammetry) or final design accuracy (field survey and 3D laser scanning).
Having all of the compiled data in a single platform ensured uniformity and consistency of the final deliverables. As an additional benefit, overlaying the conventional survey collected data and the 3D laser scanning data on the photogrammetric model provided redundancy and an additional level of confidence in the topographic mapping accuracy.
Having solved the problems of collecting and integrating the high-accuracy data, the Rick team faced one final challenge. A complex network of utilities runs along the surface and below Santa Monica Boulevard North. This network is so complicated and multilayered that the surveyors knew they would not be able to compile all of the necessary field data through traditional means without numerous site visits, which could potentially delay the city’s roadway rehabilitation schedule.
Instead, Rick used the scanning results to process and publish an Internet-based viewing tool, TruView, which allows virtual sight walks as future planning and design proceeds. This tool is similar in concept to Google’s Street View Map feature but is in an environment where planning-level measurements can be performed and used as a collaboration tool with all project design disciplines. The published TruViews are also made accessible directly though the Google Earth Viewer.
Prior to this project, the City of Beverly Hills had no previous experience with laser scanning. The survey team successfully demonstrated the advantages, such as efficiency and safety, the multitude of applications, and the accuracy capabilities that would meet the city’s need for detailed existing road conditions. “The overall advantages of 3D scanning are pretty much endless for both the surveyor and the client,” says Anne Zaworski, PE, principal civil engineer for the City of Beverly Hills. “The TruView web viewing technology eliminates additional/repeat field visits for the surveyor; offers real field measurement capabilities to all users (+/-3-inch accuracy) without having to leave their desk; saves money on both staff and travel time; achieves high accuracy measurements in the software, which uses the ‘combined surveys base’; and provides a street view to aid in field assessment from the office.”
By merging laser scanning with aerial photogrammetry and traditional methods, Rick provided a comprehensive, highly accurate dataset within the required timeframe and with no traffic disruptions. The Santa Monica Boulevard North topographic and utility map has been recognized by 3D laser scanning industry leaders as an excellent example of the benefits and diverse uses of this maturing technology. Even more importantly, the dataset will provide ongoing value as the city begins the detailed design and construction phases of the rehabilitation project and evaluates future improvements. “It was very convenient and efficient to have the entire topographic and utility survey project done through a single responsive service provider that handled the entire project, from LiDAR to topographic and utility plan preparation,” Zaworski says. “The 3D rendered view provided by Rick Engineering for our upcoming detailed design phase should further assist our still-to-be-selected designers in seeing clearly the effect of the final design in the field, even before any construction starts.”
Project Tools• Topcon total stations/GPS – conventional surveying/survey control
• Leica ScanStation 2 – time of flight scanner
• Leica Cyclone – scanning post processing, compilation, web viewer publications
• Bentley MicroStation – map sheet creation, drafting
• Bentley InRoads Survey – field to finish, office calculations, ROW analysis
• KLT Atlas/DSP - photogrammetry platform, topography editing
• Autodesk AutoCAD – final deliverable preparation