Maintaining coordinate integrity when combining survey drawings from different sources

[indiancad]

In infrastructure projects, survey data may arrive from multiple contractors using different coordinate systems, local benchmarks, or grid references. Each drawing can appear internally correct, yet combining them may introduce positional discrepancies across roads, boundaries, and utility layouts.

Simply aligning visible reference points may hide systematic coordinate or rotation errors.

What verification process do you follow before combining survey DWGs from different sources? Do you validate control points, coordinate transformations, grid-to-ground corrections, or use another method?