Outdoor-Indoor Transitions with Multiset

This guide explains how to create seamless outdoor-to-indoor augmented reality experiences by transitioning from the Global Positioning System (GPS) to a Visual Positioning System (VPS). This is a common use case for applications that guide users from an outdoor environment into a building, where GPS signals are unreliable.

Unifying Coordinate Systems with Georeferencing

By georeferencing your 3D scans, you can ensure that your application uses a single, unified world coordinate system (WGS 84). This means that all your AR content, whether placed outdoors or indoors, will exist in the same coordinate space. This is a crucial step in simplifying the transition between GPS and VPS.

When you provide the WGS 84 coordinates of your map's origin and its orientation relative to true north, Multiset can provide localization responses in the WGS 84 system. This feature, known as GeoHint, uses approximate GPS readings to narrow down the search space for localization, which improves both the speed and accuracy of pose estimation.[1]

The key benefits of this approach include:

• Improved Performance: Reduces the computational resources required for localization.

• Faster Localization: Achieves a quicker initial positioning of the user's device.

• Higher Accuracy: Helps to resolve any visual ambiguities in environments that look similar.

• Seamless Transitions: Enables smooth transitions between different mapped areas.

Managing Accuracy in GPS-Only and VPS Areas

It is important to understand the difference in accuracy between GPS and VPS. In areas where you have not scanned and are relying solely on GPS, the accuracy of your AR experience will be limited by the precision of the GPS signal. This can result in AR content that is not perfectly aligned with the real world.

To address this, we recommend the following:

• Scan all critical areas: For AR experiences that require high precision, it is best to scan the entire area to enable VPS localization.

• Design for low precision in GPS-only zones: In areas where you are transitioning from outdoors to indoors and relying on GPS, design AR experiences that do not require high precision. For example, a simple navigation arrow guiding a user towards a building entrance is a good use case for a GPS-only zone, with the VPS taking over for more precise AR experiences once inside.