State Departments of Transportation (DOT) govern the most lucrative and highly regulated civil contracts in the United States. To combat the Grid-vs-Ground scaling errors inherent in standard State Plane systems, many DOTs have abandoned standard SPCS in favor of hyper-localized Low Distortion Projections (LDPs) or bespoke county-level surface grids.
The Subcontractor Knowledge Gap
While the DOT engineers understand the LDP mathematics, private sub-contractors handling the paving and grading often do not. A grading contractor might receive a CAD file natively projected in 'Wisconsin County Coordinate System (WCCS) —Dane County' and mistakenly tell their GPS rovers they are working in standard 'Wisconsin South State Plane NAD83'.
Encroachment on Private Domain
Because the fundamental scaling math is slightly different, the 15-mile highway widening project slowly diverges from reality. By mile 14, the physical highway curve might encroach 4 feet outside the legally purchased DOT right-of-way, illegally seizing private farmland and triggering an injunction that halts a $200 Million construction project instantly.