A recent project celebrated 100 years of geodetic and photogrammetric innovation by 3D scanning an iconic WILD T2 theodolite from the 1927 series. An app has also been developed for Android, iOS and Windows devices.
Modern didactic and historical research related to digital humanities requires 3D digitization and revitalization of technological heritage. An example of such a project is the decision to celebrate 100 years of great innovations in the development of geodetic and photogrammetric instruments by 3D scanning an iconic WILD T2 theodolite from the 1927 series and developing an application for Android, iOS devices and Windows.
WILD Heerbrugg, now owned by Hexagon subsidiary Leica Geosystems, celebrated its centenary earlier this year. It all started in the late fall of 1920 with a telegram from Heinrich Wild, then head of the geodetic instruments department at Carl Zeiss, Jena, Germany, to Dr Robert Helbling, mountaineer, mountain cartographer and owner of a surveying office. surveying in Flums, Switzerland: “I have designed a new autograph for photogrammetric map production, which will be much cheaper than the model currently on the market”. Looking for a sponsor to start a new business, Dr. Helbling contacted Jacob Schmidheiny, an influential and well-respected entrepreneur from the Alpine Rhine Valley. After lengthy contract negotiations, the partnership agreement for the new company called “Heinrich Wild, Werkstätte für Feinmechanik und Optik, Heerbrugg” was signed on April 26, 1921. The new company started with about 30 employees.
In addition to designing the autograph, Heinrich Wild began to design and build a photo theodolite and, simultaneously, the famous T series: the T1, T2 and T3. The WILD T2 was designed as a universal theodolite, with an angular measurement accuracy of 1 arc second and revolutionary characteristics. The old arc-second or so-called “repeating” theodolites were large and difficult to use (Fig. 1), so the T2 quickly became popular. In fact, over 90,000 units have been sold over seven decades. So what made the WILD T2 so special?
About the SAUVAGE T2
When designing the Theodolite T2 as a further upgrade to the ZEISS T1, the following features were important to Heinrich Wild:
– Very compact telescope with 24x magnification, internal focusing and illuminating lens.
– Cylindrical upright shaft in hardened steel and mounted on ball bearings (Fig. 2a)
– Glass circles with a reading accuracy of 1 arc second and therefore a very precise engraving of the graduation lines (0.15μm) (Fig. 2b)
– Coincidence microscopes for horizontal and vertical circles for reading the locations of diametrically pitch circles (Fig. 3b)
– Very compact and closed housing weighing approximately 4.5 kg
– Dustproof container for easy transport
The coincidence microscope for reading the two positions of the diametral pitch circle was performed by a flat plate micrometer and allowed a significant time saving compared to the reading of only one position of the pitch circle (Fig. 3a).
In 1923, the first 24 instruments were delivered, despite the unfavorable conditions of mass production. Difficulties included the production of horizontal circles (d=90mm) and vertical circles (d=70mm). These were made of glass, which was a novelty at the time as they had previously been made of brass. The first devices were delivered in noble black/white (about 1,800 pieces). The transition to classic WILD green happened in 1927.
In response to sustained worldwide demand, the WILD T2 continued to be produced until 1995 and was adapted to technological advances over the decades. For example, the partial digitization of the glass circles in 1972 avoided errors in ten-minute readings.
WILD T2 app design
It is widely recognized that animated and dynamic models help foster a better understanding of design elements, digitally open up information to members of the public, and inspire young people about possible fields of study or future career options. This new form of didactics is also known as “educational entertainment” or “educational entertainment”. This form of presentation and visualization will almost certainly help spark young people’s interest and fascination with 3D scanning technology, technological heritage preservation activities, and perhaps even geodetic instrumentation. Thus, in the summer of 2020, the three authors decided to develop an interactive 3D application presenting the iconic WILD T2.
First, a storyboard was created to guide all stages of app design. It tells 15 stories in total – including the founding of the company, the features of the WILD T2 and the interior elements of the theodolite. Static and animated audio messages, images, and 3D models are embedded into the historical text. Animations are generated by 3D interactive computer graphics, to keep users interested in different stories and to highlight some important features. The app is available in German, English and Chinese (Mandarin) (Fig. 4).
The 3D scan was based on a 1927 series WILD T2. It was scanned by a composite of up to 800 photos and transformed into a colored 3D point cloud by photogrammetric beam block adjustment (based on the structure from movement, SfM) and dense image matching (DIM) (Fig. 5).
Since the colored point cloud of the WILD T2 was around 600 MB in size, it could not serve as a 3D base model in the application. Therefore, a transformation process was needed to convert the point cloud into a vectorized 3D model. Techniques to automatically transform point clouds into 3D kinematic models, for example using machine learning (ML) and deep learning (DL) methods, are still in their infancy and therefore have a very limited application, although this may fundamentally change in the next five to ten years. In this case, the point cloud was transformed into 3D CAD elements in an interactive computer graphics process called Constructive Solid Geometry (CSG). This breaks the point cloud model down into its vector components and these are then textured accordingly (Fig. 6). The 3D model of the CSG can then be textured with the WILD T2 texture of the last decades, animated and dynamized as desired: rotation around the alidade axis, crossing of the telescope, tilt and zoom. Additionally, a decomposition into optical components (using sectional drawings) allows camera flights along ray paths for horizontal and vertical circles, representation of axis systems, and much more. App users can also play with the 3D virtual reality (VR) model – or “digital twin” – of the T2.
The app works in panning mode and the screen is divided into three parts: story titles on the left, stories with pictures in the middle, and help symbols on the right. 3D models and animations are displayed in the middle of the screen and symbolized by the rotating cube symbol. The top left buttons lead to story titles and the home screen. Embedded audio in matching stories can be activated using the speaker button. The 15 stories provide app users with a comprehensive overview of the history of the company and its locations over time, T2 features and updates, and some of the theodolite’s interior items that are animated to demonstrate its compact and revolutionary design.
Animations and rendering
All interactive computer graphics 3D models were generated using Autodesk 3ds MAX. Point clouds were used only to scale the final 3D CSG model. Photos of the T2 over time (1923-1995) were used to texture the digital twins, according to a chosen moment. The application offers three digital twins for the following time periods: 1922, 1929 and 1962. Several sectional models (one of which is shown in Fig. 7) were used to create a very detailed 3D model with many elements of design, which the user can also “explode”. This feature aims to inspire the younger generation on the possibilities of interactive computer graphics, which can also be used to provide impressive animations and simulations in sectors where 3D data capture is emerging, such as architecture, engineering and construction (AEC).
3D text, audio, image sequences and 3D models have been integrated into the application using the Unity 3D game engine. This allowed animated interactive 3D models to be exported and rendered and finally prepared for mobile operating systems, such as Android and iOS. During this processing step, a Windows version was also generated to be scaled for multiple screen resolutions. Figure 8 shows an excerpt from Story 15, featuring animated flights through the horizontal and vertical circle reading optical systems.
The WILD T2 theodolite was a milestone in the development of surveying instruments. For over seven decades it had the most modern design and revolutionary features of its time, such as cylindrical vertical axis, horizontal and vertical glass circles, diametrically readable graduated circles, precise readings by micrometers coincidentally, a compact telescope and a low weight. By summarizing the most important facts and features of this innovative and best-selling theodolite, the WILD T2 app recognizes the outstanding performance of Heerbrugg engineers, technicians and managers, within the company known today as Leica Geosystems and part of Hexagon – for the past 100 years. The developers hope that the WILD T2 app will contribute to public understanding of science and technology by presenting 15 stories about the background of WILD Heerbrugg and the T2, including a variety of 3D reconstructions, visualizations, animations, image sequences and audio. In these times of digitization and new didactic elements in higher education, it is hoped that the application will help students but also the general public to better understand the history of geodesy and geoinformation sciences through the use fun with new technologies.
Download the WILD T2 app for free: