Target point coordinates, minimum point counts, and repeatability tolerances for internal electro-optical tank calibration (API MPMS Chapter 2, Section 2D)
◉ API MPMS 2.2D-2003 STYLE CHECK · NOT A REGULATORY SUBMISSION TOOL
⚠ Indicative tool only, and deliberately narrow in scope. Section 2D covers the field measurement procedure, not the full capacity table. Two things it does NOT give a formula for, and this tool doesn't either: (1) reducing a level's set of (X, Y) target-point coordinates down to a single internal radius — §B.3 explicitly defers this to "established mathematical techniques" (in practice, typically a least-squares circle fit) without specifying one; (2) capacity table development itself, including corrections for hydrostatic head, shell temperature, deadwood, and tilt — §12.2 explicitly defers all of this to API MPMS Chapter 2.2A, a different document not available here. Equations B-1–B-3 were verified by zooming into the source page image directly, since Equation B-2 uses an unusual sin(θ)·sin(φ) form rather than the more familiar cos(φ)·sin(θ) — confirmed as printed, not a misread.
Identification
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Target Point Coordinate Conversion (Equations B-1 to B-3)
X = D·cosθ·cosφ Y = D·sinθ·sinφ Z = D·sinφ (as printed in the standard).
Result
X—
Y—
Z—
To go from a level's set of (X, Y) points to a single internal radius, §B.3 defers to "established mathematical techniques" without naming one — not something this tool computes. In practice this is typically done as a least-squares circle fit across all target points measured at that level.
Minimum Target Points Per Set (Table 1, §8)
Two sets of target points are used per course (§8.1) — one 1/5–1/4 of course height above the lower horizontal seam, one the same distance below the upper seam. Target points must also stay ≥300mm from any vertical welded seam (§8.2).