Visualizing the Z -Value Uncertainty in 3D Utility Models

3D utility models are becoming more prevalent for transportation design as Departments of Transportation shift to models as contract documents. Models consist of shape elements with x, y, z values plus attributes such as size, material, ownership, and so on. ASCE 75-22, Standard Guideline for Recording and Exchanging Utility Infrastructure Data, was developed to standardize attribute and locational data for newly installed infrastructure that can be physically measured and verified and used to build 3D models. But most 3D models of utilities consist of indirect engineering judgments of utilities already buried and hidden in the ground. ASCE 38-22, Standard Guideline for Investigating and Documenting Existing Utilities, was developed to primarily categorize the uncertainty of the x, y component of utilities in 2D plan sets. Visualization of that uncertainty is categorized by affixing one of four Utility Quality Levels to a utility segment. Visualization of the Utility Quality Level is primarily by labeling, use of CAD layers, line style, or other distinguishing methods. Depths of utilities below the surface datum are determined from varied measurement methods and judgments, as is the certainty of the depth portrayed compared to the actual physical location. These measurement methods and judgments are similar but different from a Utility Quality Level and need a "scale" of uncertainty that can be quantified and visualized. Accurate location is inexorably tied to the size and shape of the utility element, which may also be unknown or uncertain. This paper proposes a method for defining the uncertainty of the z element of 3D utility model elements and a subsequent method of visualizing that uncertainty for the benefit of planners, designers, and constructors who are relying upon that data for direct and indirect clash detection.