Mapping the Scene vs. Modeling the Object: Site and Transportation Information Modeling (SIM & TIM) for Design and Construction
A note from Continental Mapping President, Dave Hart, CP
If you look at the stack of professional mapping, survey, and GIS publications on your desk, you will rarely find an issue that doesn't highlight a new and different application of lidar. With dozens of sensor configurations and applications, lidar has deservedly become the hottest technology in the survey and mapping profession.
Very high accuracy design grade surveying and mapping services are fast becoming the norm, especially with transportation clients. These are demanding projects, but its the need to interact with the data in a true 3D design environment that presents the biggest challenge. In order to determine the deliverables and data needed by the designer, two things are needed: a deeper understanding of how the data will be used throughout the design and construction process, and a clear understanding of critical data needs for the design process. Understanding these needs allows us to develop a project design that interconnects mapping the scene and modeling the object.
To address this, Continental Mapping is leveraging our experience and proven Building Information Modeling (BIM) concepts to develop and apply Site Information Modeling (SIM) and Transportation Information Modeling (TIM) specifications for our clients.
Our clients need high accuracy 3D data capable of supporting the full life cycle of planning, design, and construction. From the photogrammetrist's perspective, the specifications used to build that data were typically determined by map scale and contour accuracy. But with the use of terrestrial, mobile, and aerial lidar sensors, we can collect more data that represents a full 3D visualization. Those technical advancements, in conjunction with the desire to design in true 3D, have fundamentally changed the way we approach high accuracy projects. Field collection that combines survey with (sometimes) multi-platform lidar and imagery is rapidly becoming common practice.
Today we focus on:
- Identifying what 3D features are critical to the design process. Which are referential in nature only?
- Defining the appropriate level of detail (LOD) to represent the 3D features of interest and thereby support end user requirements.
- Applying spatial data design concepts to define entities that will be constructed from the point cloud as well as attributes for and relationships between those entities.
- Understanding the difference between the need for a measurement, like a minimum vertical clearance, and a model, which requires guidance for its construction.
- Translating conceptual definitions of logical spatial database design that can be represented in a CADD or GIS format.
At Continental Mapping, we have spent a large part of 2012 building SIM & TIM specifications. Continental Mapping's SIM/TIM specifications development has been largely influenced by practical experiences in developing deliverables for our US Army Corps of Engineers and transportation clients. Addressing issues like point limit import restrictions, refresh speed for rendered models, level of detail requirements, and understanding of design and construction needs, have helped us build realistic SIM/TIM specifications for terrestrial and mobile lidar projects.
We are continuing to enhance our SIM/TIM specifications development, and look forward to learning from, working with, and educating our engineering clients to further enhance our offering to help them succeed.