NH-66 Coastal Highway Progress Mapping

The problem

Monthly RA bills on a highway package are argued over quantities – how much earth actually moved, and when. The contractor's cross-section returns and the client's site engineers were reconciling by hand, and two disputes had already escalated past the engineer to a claims process.

The alignment also crossed nine water bodies and 4 km of Coastal Regulation Zone, where the environmental compliance record needed to be photographic and dated, not narrative.

What we did

We set up 96 permanent control monuments along the alignment at the first mobilisation and observed them once with long-occupation DGPS. Every subsequent monthly cycle flew against those same monuments, which is what makes month-to-month volumes genuinely comparable rather than approximately similar.

Each cycle produced an orthomosaic, a DTM and a cut-fill surface differenced against the previous month and against the original ground model. Volumes were reported per chainage block matching the contractor's own billing breakup, so the numbers landed in a format both sides could argue from directly.

CRZ segments got a separate dated photographic set filed to the environmental consultant each cycle.

The outcome

Two claims that had reached the engineer were withdrawn once the dated volume series was tabled – in both cases the drone record supported the contractor on one item and the client on another, which is roughly what an honest measurement does.

RA bill certification time fell from an average of 19 days to 6. After cycle eight the client made the aerial volume the primary measurement for interim certification, with cross-sections retained as a check.

“Monthly progress mapping saved us two claim disputes in the first quarter alone. Having a dated, georeferenced record changed how our contract meetings run.”

Karthik Subramanian, Chief Engineer, Coastal Highways Corporation