TIN-based earthwork is the bid-grade alternative to manual grid methods. Where a grid takes one elevation per cell and approximates the surface as a stack of prisms, a TIN connects every contour and design line into a continuous surface — capturing every break-line, slope change, and elevation transition in the data.
SiteWorx/OS reads existing-grade contours from the PDF or DWG, builds the existing TIN, then builds a separate proposed-grade TIN from the design lines. Volume between the two surfaces is computed by integrating the height difference across the surface area — exact for the source data.
Compared to the grid method, TIN-based volumes capture site variation that grid cells average away. For most commercial sitework, TIN volumes match surveyor calculations within 1-2%; grid volumes can drift 5-15% on sites with significant elevation change.