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The Grid is a building’s coordinate system. Grid lines (A, B, C / 1, 2, 3) are shared across every discipline and every floor in a drawing set. Grid intersection “B-3” refers to the same physical location on the architectural, structural, mechanical, electrical, plumbing, and fire protection sheets. This is how trades coordinate: “the duct at B-3 clashes with the beam at B-3.”

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Three models

The grid system uses three entities:
A project can have multiple Grids — for campus projects with multiple buildings, buildings with rotated wings, or additions. Each Grid is an independent coordinate system. Within a single building, the grid is the same on every floor (it extrudes vertically through the structure), so a 50-story building still has one Grid.

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Cross-block alignment

Grid lines serve as shared control points for aligning coordinates across different blocks. When Bedrock detects grid lines on a VIEW block, it creates BlockGridLine entries recording each grid line’s normalized position (0-1000) within that block. Two blocks that share the same GridLines can be spatially aligned by mapping through these control points.
Both blocks reference the same GridLine records (“A”, “B”, “C”). The shared grid lines act as anchor points for computing an affine transform between the two blocks’ coordinate spaces.

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How alignment works

To check if a duct on M-101 clashes with a beam on S-201:
  1. The duct Feature on M-101 has bounds at position 350-650 (between grid A and C)
  2. The beam Feature on S-201 has bounds at position 420-720 (between grid B and C)
  3. Using shared grid lines as control points, compute an affine transform between the two coordinate spaces
  4. Map the duct’s position into the structural block’s space
  5. Detect that they overlap near grid B — potential clash
This works across:
  • Different disciplines on the same floor (architectural vs structural vs MEP)
  • Different floors of the same building (same Grid, different sheets)
  • Different revisions of the same sheet (grid lines are stable across revisions)
Grid-based alignment is more robust than pure image alignment because grid lines are semantically meaningful anchors. They do not shift between revisions or vary between disciplines the way drawing content does.

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Key fields

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Grid

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GridLine

Unique constraint: (grid_id, label) — no duplicate labels within a grid.

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BlockGridLine

Unique constraint: (block_id, grid_line_id) — each grid line appears at most once per block.

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Grid intersection queries

Query features by grid intersection to find everything at a specific location across all disciplines:
Returns all features near grid intersection B-3 across all sheets and disciplines.

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Use cases

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Next steps

Relations

How cross-references work.