Laser scanner survey and 3D textured model: Bourgeoisie de Sion (Switzerland)

Context

The town of Sion (Valais, Switzerland) consists of two distinct parts : the modern and the medieval. The medieval town is governed by the public corporation known as “La Bourgeoisie” and is extremely well preserved. Its rich heritage includes the following notable monuments: the Château de la Majorie, the Hôtel de Ville (Town Hall), Georges Supersaxo’s house, the casino housing the cantonal parliament, the Cathedral of Notre Dame de Sion, the Chapter House and the church of SaintThéodule.

En partenariat avec Géomètres Centre SA.

The problem

No reliable technical data existed for the Bourgeoisie and Supersaxo Halls, two fine historic interiors in the old town of Sion. The SBMA, the agency responsible for protecting Sion’s cultural heritage, sought to obtain suitable documentation in order to improve communication concerning these architectural jewels.

The project setting

• Two historic interiors in the commune of Sion in Switzerland
• Sites scanned at high density (1 point per cm)

Objective

• To obtain reliable technical data for both halls
• To create animated films for communication purposes

The requirement

• 3D model of each interior in AutoCAD format
• 3D textured models for each in 3ds Max
• Animated film for each hall

Constraints

• Required accuracy: 2 cm
• Cramped and very poorly lighted spaces

Our responses

Laser scanner and photogrammetric surveys enabled us to meet all the requirements. The laser scanner survey yielded a complete 3D archive of the geometry of each hall with an accuracy of the order of 5 mm. The photogrammetry allowed us to position the textured images with similar accuracy thanks to computation using TPLM-3D’s own ImgSurveyor software.

The 3D modelling process produced a final accuracy of the order of 2 cm.

The data supplied to the client thus completely satisifed the requirements of the two tasks:

• 3D modelling accuracy in AutoCAD was based totally on the point cloud of 5 mm accuracy; the reduced accuracy of the final result was due to simplifications aimed at reducing the filesizes (12 Mb per interior for the final 3D model).

• Animated films in 3ds Max (the current standard format). Our data can thus be reworked without difficulty by any specialist in this type of work.

Deliverables

• 3D models of the two interiors in .dwg format.