On 26. April 2021, WILD Heerbrugg, today Leica Geosystems AG, part of Hexagon, will be 100 years old. 100 years of great innovations in the development of geodetic and photogrammetric instruments, great developers, engineers and managers. It all started in late autumn 1920 with a telegram from Heinrich Wild, at that time head of the Geodetic Instruments Department at Carl Zeiss, Jena, Germany, to Dr. Robert Helbling, mountaineer, mountain cartographer and owner of a surveying office in Flums, Switzerland: "I have designed a new autograph for the photogrammetric production of maps, which will be much cheaper than the model currently on the market". In search of a sponsor to establish a new company, Dr. Helbling approached Jacob Schmidheiny, an influential and highly respected industrialist from the Alpine Rhine Valley. After extensive contract negotiations, the partnership agreement for the new company "Heinrich Wild, Werkstätte für Feinmechanik und Optik, Heerbrugg" was signed on 26. April 1921. The new company started with about 30 employees.
Heinrich Wild, in addition to designing the autograph, began designing and building a phototheodolite and the world famous T series: the T1, T2 and T3. The WILD T2 was designed as a universal theodolite, with an angular measurement precision of 1" and revolutionary features. Previous arc-second theodolites were large and difficult to use, the so-called “repetitive theodolites” (Fig. 1), so the T2 became a "best seller" from the beginning. It sold more than 90,000 units in 73 years. No other theodolite has ever been able to achieve this high demand. Why was the WILD T2 so special?
Fig. 1: Repetitive theodolites and the WILD T2 – a size comparison.
Heinrich Wild had already designed the Th I theodolite at Carl Zeiss, Jena, before he wanted to build the equivalent, but even improved T2 theodolite in his own company. The following features were important to him:
- Very compact telescope with 24x magnification, internal focusing lens and to be illuminated.
- Cylindrical standing axis made of hardened steel and mounted on ball bearings (Fig. 2a).
- Glass circles with 1" reading precision and therefore very precise etching of the graduation lines (0.15 μm) were necessary (Fig. 2b).
- Coincidence microscopes for horizontal and vertical circles for reading diametrical pitch circle locations (Fig. 3b).
- Very compact and closed housing weighing about 4.5kg.
- Dust-tight container for easy transport.
Fig. 2: Ball-beared cylindrical standing axis and diametrical readable glas circles
The coincidence microscope for reading the two diametral pitch circle positions was realised by a plane plate micrometer and brought great time savings compared to the reading of only one pitch circle position (Fig. 3a).
In 1923, the first 24 instruments were delivered, despite adverse conditions in series production. Difficulties included the production of the horizontal circles (d=90 mm) and vertical circles (d=70 mm) made of glass, a novelty at that time, as these had previously been made of brass. The first devices were delivered in noble black/white (about 1,800 pieces), in 1927 the transition to the classic WILD green took place.
Fig. 3: Number of reading points at the glass circles: (a) Beam path with one reading point; (b) Mirroring two reading points together.
The WILD T2 was built until 1995 due to the large worldwide demand and was adapted to technological progress over the decades. A partial digitization of the glas circles in 1972 was able to avoid errors in the ten-minute readings.
Fig. 4: Der WILD T2 over time – the basic design elements have been retained.
Modern didactic and historical research in the field of Digital Humanities requires 3D digitization and dynamization of important design elements. The WILD T2 represents a prime example of such a project. In coordination with Hexagon Geosystems, Heerbrugg, it was decided in 2019 to make a WILD T2 from 1927 available (Fig. 4b). This was imaged by a composite of up to 800 photos and transformed into a colored 3D point cloud by photogrammetric bundle block adjustment (Structure-from-Motion, SfM) and Dense Image Matching (DIM) (Fig. 5).
Fig. 5: Photogrammetric digitization of the WILD T2: (a) Photo bundle and (b) 3D point cloud
In a further step, a CAD model was created using interactive computer graphics, also known as a CSG model (Constructive Solid Geometry). In this process, the point cloud model is broken down into its vectorial components and these are then textured accordingly (Fig. 6). This 3D model can now be dynamized as desired: Rotation around the alidade axis, telescope traversal, decomposition into the optical components (using sectional drawings), camera flight along the ray paths for horizontal and vertical circles, representation of axis systems, and much more. This dynamic model helps to better understand design elements, to inspire students for geodetic instrumentation and to digitally "open up" and comprehend previously closed exhibits to laymen. This modern form of didactics is also known as "education entertainment" or "edutainment" for short, and is just beginning to emerge. The digitization of technological cultural heritage - also referred to as Tech Heritage (TH) - is an important task that not only interests the scientific community, but also helps companies like Hexagon to understand their past and to remember to the past great designers, engineers, technicians, managers and above all, great products.
Fig. 6: Interactive 3D-Modeling and texturing using computer graphics.
It is now impossible to imagine daily life without using mobile devices (smartphones and tablets). Everyone uses applications (apps) to display certain information on their mobile device. For this reason, the "WILD T2 App" is currently being developed in close cooperation with Hexagon Geosystems, Heerbrugg, by means of which the history of WILD Heerbrugg, a short CV of Heinrich Wild, the design elements of the WILD T2, the 3D reconstructions and animations can be accessed. The app is published in German, English and Chinese (Mandarin) to reflect the worldwide significance of the iconic WILD T2 - it will be available in time for the 100th anniversary. Further reading on the subject is provided below.
Deumlich, F. (1972): Instrumentenkunde der Vermessungstechnik. VEB Verlag für Bauwesen, Berlin. 332S.
Fritsch, D., Wagner, J.W., Simon, S., Ceranski, B., Niklaus, M., Zhan, K. & Wang, Z. (2018): Gyrolog—Towards VR Preservations of Gyro Instruments for Historical and Didactical Research. In 2018 Pacific Neighborhood Consortium Annual Conference and Joint Meetings (PNC), San Francisco, CA, USA, 27–30 October 2018, pp. 1–7, doi:10.23919/PNC.2018
Fritsch, D., Wagner, J.W., Ceranski, B., Simon, S., Niklaus, M., Zhan, K. & Mammadov, G. (2021). Making Historical Gyroscopes Alive – 2D and 3D Preservations by Sensor Fusion and Open Data Access. Sensors, 20th Anniversary Issue. 31p.
Grossman, W. (1969): Vermessungskunde. II Horizontalaufnahmen und ebene Rechnungen. Sammlung Göschen, Band 469/469a
Simmen, R. (1991): Von Wild zu Leica – 70 Jahre Firmengeschichte. Eigenverlag Leica Geosystems.