Technological developments

App software

The ALApp project is advancing an existing software for smartphones and tablets, which presents the archaeology of extant sites of the Frontiers of the Roman Empire. The current application (app) platform uses conventional audio, photos, text and videos. Apart from improvements in computing speed, stability and user-friendliness, the platform development consists of the integration of three-dimensional (3D) reconstructions as both virtual and augmented reality, including rotatable 3D objects, 360° landscape views, geotagging and landscape recognition. The platform will be used to create two apps: one for six sites the Antonine Wall in Scotland; the other for the Upper German-Raetian Limes at Eining in Upper Bavaria. Both apps are produced for the operating systems Andriod and iOS and are available from their respective online stores, GooglePlay and iTunes. The ALApp project partners intend to produce after project completion more content for other archaeological sites of the Antonine Wall and the German Limes as well as to transfer the app platform to other sections of the Frontiers of the Roman Empire.

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App platform

Modern smartphones and tablets are powerful computing devices. They are equipped with GPS receivers, to establish the device’s position on the Earth, and magnetic field sensors and accelerators, to identify the direction to which the device points. Their screens can display still and moving imagery, including text and animations. They can also show in real-time the image captured by the in-built camera. And in-built loudspeakers output speech, music and other sounds. All of these features are utilised in ALApp’s app platform. The devices’ screens can display still and moving imagery, including text and animations. They can also show in real-time the image taken by the devices’ cameras. And loudspeakers output speech, music and other sounds. All of these features are utilised in ALApp’s app platform.

The ALApp platform is based on an earlier version, developed for an app presenting archaeological sites of the Frontiers of the Roman Empire in Bavaria, the Germanic Limes Middle Franconia. Developed in 2013 with financial support from the Bavarian Savings Bank Foundation, this Limes Mittelfranken Mobil app, available at GooglePlay and iTunes, used text with pictures as well as audio and video. The app included a set of maps, on which the app users could find a point of interest (PoI), a location, for which information was available in the app. The GPS receiver was used to show the position of the user on the app’s maps and to alert the user when approaching a PoI. The app displays content off-line, so that an internet connection is not mandatory, which is especially important for remote regions with limited mobile network coverage and for users not wanting to use such networks, for example, visitors from abroad.

In addition to all of these features, the ALApp project enhances the user’s app experience by integrating into the platform 360° surround views of archaeological sites, the display of 3D reconstruction of former buildings and other built structures on the sites, as well as interactive animations of 3D models of archaeological objects discovered on the sites. With these additional features, the sites can be explored virtually – from home, a hotel or anywhere in the world. With the display of 3D objects, the ALApp platform aims at linking the objects’ sites of provenance to the museums now storing and exhibiting these objects. Similarly, the app can be used in the museums to provide information about the archaeological sites on the spot. Finally, a special feature of the ALApp platform is augmented reality. This technology will allow users at the archaeological sites to experience 3D reconstructions right at the location where they would have stood originally: Using the camera of the smartphone or tablet, 3D reconstruction will appear directly overlayed onto the camera’s image, as if the structures were still standing today.

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Virtual reality

The ALApp app can display interactively 3D models and 360° views of sceneries. The latter will enable app users to view an archaeological site remotely, as if they were actually present on the site. Users can scroll the view to the left or right using buttons and gestures, but they can also use their device like a camera. Pointing northwards will display the site’s north-facing scenery. Turning towards another direction will turn the scenery also, as if viewing the landscape at the real location.

Similarly interactive concepts are used for the display of digital 3D models. In ALApp, these models are either reconstructions of buildings and other structures, which once stood on the archaeological sites, or 3D scans of archaeological artefacts, found at the sites, but now stored off-site. The app users can rotate all of these objects on their screens, to view them from any angle, including the base and rear surfaces, often not viewable when on display in a museum. The shoe depicted here on the app’s user interface, for example, is a scan of a child’s shoe, found during the excavation of a well at the fort of Barr Hill, a site of the Antonine Wall in Scotland. Now stored at the Huntarian Art Gallery & Museum in Glasgow, the show was scanned to create the displayed 3D model, which the app user can rotate at their perusal, viewing the shoe from all sides, including the underside of the sole.

The reconstructions of built structures can be viewed as objects in their own right, but will also be overlayed onto the 360° surround views, to help app users imaging these structures better in today’s landscapes.

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Augmented reality

To particularly enrich the users’ experience of viewing 3D reconstructions at their original locations, the ALApp project integrates augmented reality in the app platform. Augmented reality makes use of the cameras of smartphones and tablets by overlaying the image produced with additional information about the site, ranging from georeferenced annotation to full 3D reconstructions.Thereby, the app user can view on-site reconstructions of buildings and other built structures, by pointing the camera at the point where they would have stood originally. This is the technology, which location-based computer games, such as Ingress and Pokémon Go, use to show fictive characters on smartphone or tablet screens, placed onto the actual image from the devices’ cameras. Similarly, the users of the ALApp app can view on-site reconstructions of buildings and other built structures overlayed onto their camera image, by simply pointing the camera at a specific location.

Two location options will be used for this in ALApp: The user can either point the camera at a 2D plan or other drawings of the model’s structure. In the image seen here, the camera is looking at the floor plan of a fortified Roman tower. The app recognises the floor plan and overlays it with the tower’s 3D reconstruction. Such markers, in the form of drawings or other graphics, will be placed on interpretation panels located at the archaeological sites. The other option is to point the camera directly into the landscape, where the app will recognise either scenery landmark or fiducial markers installed on site. Thereby, the user can view 3D reconstructions of buildings and other structures at the place where they would have stood originally, overlayed onto the camera’s image of the landscape, as captured in that very moment in time.

Various possibilities have been reviewed and tested to achieve the best augmented-reality integration, based on open-source software modules to ensure that the app can be used free of charge long-term. The use of fiducial markers is already commonplace. The best-known version is the QR code, where users point their camera at a square bar code, legible to the app reading it. Using recognition of scenery landmarks in an actual landscaped is far more sophisticated, but has the advantage that no markers need to physically installed at the archaeological sites. The difficulty of landmark recognition for the ALApp app is that many of the archaeological sites of the Frontiers of the Roman Empire are located in vegetation-rich places. Seasons changes, such as foliage change in the vegetation or snow cover of the terrain) will thereby have a substantial impact on the app’s recognition ability. Depending on the archaeological site, the ALApp platform will use either fiducial markers or scenery landmark recognition – or a mix of the two.