Project № 08 · Technical · Heritage

Santa Maria
Maggiore survey

A 3D-scan-based line-weight redrawing of the Loggia for the Vatican archive.

Location: Basilica di Santa Maria Maggiore, Rome
Year: 2021
Type: Architectural survey & documentation
Methods: 3D scanning, photogrammetry, point-cloud tracing
Course: Architectural Survey · Prof. C. Bianchini
Team: L. Duarte Longarezi, K. Matsushima & H. Alsebai

Interior of the Loggia delle Benedizioni at Santa Maria Maggiore, checkerboard floor and frescoed walls — fig. 01: The Loggia delle Benedizioni. The chequered floor and Renaissance frescoes are the principal subjects of the survey.

The Vatican holds a continuous archive of measurement drawings of its principal basilicas, updated as scanning technology improves. Our brief was to add a current set for the Loggia of Santa Maria Maggiore, using terrestrial laser scanning, photogrammetry, and traditional CAD redrawing, that respects historic drawing conventions while taking advantage of digital precision.

The result is a hybrid: line-weights drawn by hand from a point cloud. Numerical accuracy comes from the scan; legibility comes from following the conventions of the archival drawings already in the basilica's record.

From point cloud to line

Two plan views of the basilica, un-surveyed left, surveyed in green right — fig. 02: Plan survey. Left: the un-surveyed plan from the existing archive. Right: our zone (highlighted green) with new scanner positions and updated geometry.

Detailed architectural section through the Loggia — fig. 03: Architectural section through the Loggia. Drawn at full archive scale, with all 22 m of vertical extent measured.

The point cloud doesn't draw, it just measures. Drawing is still a decision: which line is structural, which is ornamental, which is shadow.

Front elevation drawing of the loggia, left side — fig. 04: Front elevation, left side. Two stories with three orders of openings; the upper register hosts a relief of two angels.

Specific element analysis: door and tabernacle elevations and sections — fig. 05: Specific element analysis. Doorway elevation, vertical section, horizontal upward section, and detailed profile, the kind of drawing that reads the way a drawing did in the eighteenth century.

The element analysis (fig. 05, right) compares two reconstructions: the same window, drawn first from a 3D scanner point cloud and then from photogrammetry. They diverge in subtle places, gilded edges read differently to laser than to photo. Documentation isn't neutral; it carries a method's biases. The Vatican drawings now record both.

The project sits at the technical end of my work, but the underlying problem is one I think about often: how to translate between modes of measurement and modes of meaning. A point cloud is true; a drawing is legible. The discipline lives in moving carefully between them.