Script 05 — Volume

File: sql/scripts/main/05_calc_volume.sql
Reads from: {city2tabula_schema}.{lod_schema}_building
Writes to: {city2tabula_schema}.{lod_schema}_building (UPDATE)

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Purpose

Estimates building volume using a simple bounding-box approximation: height × footprint area. Two volume estimates are computed — one using the eave height and one using the ridge height — providing a lower and upper bound on the true volume.

This is a deliberate simplification. Computing the exact volume of a 3D building solid from CityGML would require expensive geometric operations. For the purposes of TABULA archetype matching (script 07), a height × footprint approximation is sufficiently discriminating and much faster to compute.

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What it does

UPDATE {city2tabula_schema}.{lod_schema}_building AS bf
SET
    min_volume = bf.min_height * bf.footprint_area,
    max_volume = bf.max_height * bf.footprint_area,
    min_volume_unit = 'cbm',
    max_volume_unit = 'cbm'
WHERE bf.building_feature_id IN {building_ids}

This is a straightforward UPDATE. No CTEs are needed because both operands (min_height, max_height, footprint_area) are already columns in the same row from script 04.

The CASE expressions guard against NULL inputs: if either operand is NULL (e.g. a building with no wall surfaces), the column is left unchanged rather than overwritten with NULL.

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Volume semantics

Column	Formula	Interpretation
min_volume	min_height × footprint_area	Eave-height box — excludes the roof volume. Conservative lower bound.
max_volume	max_height × footprint_area	Ridge-height box — includes the full roof height as if it were a box. Liberal upper bound.

The true building volume lies somewhere between these two values. For a building with a flat roof, min_volume and max_volume are equal.

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What comes next

Script 06 refines the storey count and overwrites the total floor area estimate.