The deliverable is confidence, not just coordinates
A definitive survey answers "where is the well?". This engagement answers the harder questions that follow: how sure are we, is it clear of the offsets, and did it hit the target? All three are questions about the ellipse of uncertainty, and all three are only as good as the error model behind them.
Uncertainty from the program actually run
We compute the ellipse of uncertainty with the current ISCWSA Rev 5 MWD error functions, using the survey program as it was actually executed: each hole section carries the instrument performance model of the tool that surveyed it, corrections included, and tie-ons propagate from surface to TD. The output is station-level NEV/HLA covariance and ellipse axes, not a default tool code pasted over the whole well.
That distinction matters, because the ellipse is not a property of the well. It is a property of how the well was surveyed and corrected. A survey processed through referencing and MSA carries a materially smaller, and different-shaped, ellipse than the same stations under a default code, and your anti-collision and target decisions should run on the real one.
Anti-collision
For a drilling program, we design the survey program to meet the separation requirements of the well plan, process the surveys against that program as they arrive, and run separation-factor scans against the offset wells. You receive clearance results computed from real, documented uncertainty on both wells, plus the station covariance your own planning software needs to reproduce them.
Because shrinking the ellipses raises the separation factor at the same physical spacing, this analysis frequently converts directly into tighter approved spacing, fewer offset shut-ins, and cleaner audits.
Geological target analysis
For the target, we combine the ellipse with the target geometry to quantify the probability of intersection, and we work the problem backwards at the planning stage: given this target and this well plan, which combination of accuracy enhancements reaches the required confidence at the lowest cost? Once drilled, the definitive survey demonstrates quantitatively that the wellbore is where the geology needed it to be.