Sizing Number

Purpose

This note defines the one-digit Numeric Suffix used to control rectangular sizing behaviour.

Source Priority

HAPI User Manual.pdf
User-confirmed project corrections
Rectangle-fitting Algorithms.md
Point Code and Style Code.md

Definition

A Sizing Number is a one-digit Numeric_Suffix appended after a Feature_Code. It explicitly specifies the exact quantity of survey points to use when constructing the enclosing rectangle of a surveyed feature.

Syntax

FeatureCode + SizingNumber

Examples:

Code	Meaning
`CP3`	Catch Pit using three points for rectangle construction.
`BN2`	Bench using two points, typically for a linear dimension.
`BN3`	Bench using three points for rectangular calculation.
`UB3`	Utility Box using three points for rectangular calculation.

Business Rules

No Sizing Number

If no Sizing Number is provided, the system uses the predefined point count from the Feature_Catalogue or legacy drafting behaviour.

Conventional Numeric Suffix Compatibility

Existing conventional feature codes with a single number, such as MT2, are treated as having a Sizing Number while preserving historical behaviour.

User-Defined Sizing Override

Appending a Sizing Number overrides the default point count and instructs the system to use exactly that number of points for geometry construction.

Three or More Points

When three or more points are specified, HAPI calculates an enclosing rectangle using a rectangle-fitting method. See Rectangle_Fitting_Rules.

Fixed-Width Symbol Behaviour

For some features, such as ET and UB, the plotted symbol may not visually reflect the full physical boundary. The calculated length and width are still important and should be stored for later ECM workflows.

Recommended Use Cases

Use Case	Why Sizing Number Helps
Ambiguous survey specification	Explicitly controls whether a feature is represented by two, three, or more points.
Obstructed corner	Allows rectangle reconstruction from accessible surveyed edges.
ECM dimensional capture	Preserves width and length data for modelling, even when 2D symbols have fixed display widths.
Legacy compatibility	Preserves conventional `1POINT` and `2POINT` behaviour while allowing modernised alternatives.

Implementation Notes

Preferred planned functions:

ResolveSizingNumber
GroupRecordsBySizingNumber
CalculateBestFitRectangle
CalculateShrinkToFitRectangle
ApplyLeftFirstOrientation

Sizing Number logic should not be mixed with Clustering Number logic. A one-digit suffix controls rectangle sizing. A two-digit suffix controls grouping.

Open Questions

Confirm whether all sizing-capable 1POINT and 2POINT features should route through the same rectangle-fitting module as POLYGON features.