Absolute Height

Previously marketed as Zed™, the location.io absolute height service provides the absolute height of a device using compensated barometric pressure, enabling floor-level accuracy for smartphones and IoT devices equipped with barometric pressure sensors.

This solution, comprised of a client software library and associated cloud-based data services, is targeted at chipset vendors, device OEMs, mobile operators and application developers seeking to integrate reliable floor level detection, whether for general Location-Based Services or compliance with E-911 regulations.

zed_system_building_500hWhether for emergency or consumer applications, the determination of a mobile device’s vertical position while indoors presents unique challenges. Given the environment, even when a GNSS receiver attains a fix, a mobile device cannot reliably use the reported altitude. Beacon-based techniques, such as those derived from Wi-Fi or Bluetooth, remain challenging as they often rely on GNSS-based crowd sourcing or costly venue characterization.

More and more sensor chips in recent smartphones include barometric sensors and this opens up a new ability to estimate altitude. However, each has unique and variable characteristics which prevent floor-level accuracy without further assistance.

The location.io absolute height service makes it possible to easily and fully exploit these new device hardware capabilities.

Features & Benefits

Floor Level Accuracy

The location.io absolute height service yields floor-level determination by correlating 2D positions with current geo-referenced barometric data to deliver a reliable vertical position estimate within 2.5-3 meters. Zed uses adaptive algorithms to combine global barometric reference pressure sources, such as Custom Weather’s, with finer grained crowd-sourced measurements and effective device sensor calibration.

When creating Location-Based Services, 2.5 to 3 meters vertical accuracy means the ability to display the correct map or dispatch responders to the right floor.



Improves Wi-Fi Indoor Solutions

A significant limitation of Wi-Fi indoor positioning technologies is the lack of a reliable altitude field in the reference database of Wi-Fi access point locations. These databases are inherently 2D as detected APs are usually crowd-sourced and geo-tagged with GNSS positions that are typically not on the same level. For example, an indoor Wi-Fi Access Point located on the 5th floor of a building may be detected at street level and recorded as such. The addition of the location.io absolute height service to any Wi-Fi based positioning system not only yields useful floor-level accuracy, but also helps refine the database of Wi-Fi AP locations.

Platform Independant

Mobile devices sport a multiplicity of sensors, from gyros to accelerometers, and more recently, barometric pressure sensors. In order to take advantage of the location.io absolute height service, device requirements are limited to having a barometric pressure sensor, a network connection and either a location or a list of cell towers or Wi-Fi Access Points. The location.io platform takes care of the rest!



POST http://location.io/locationApi HTTP /1.1
Authorization: RXN-BASIC cId=xxxxxxx,pw=xxxxxxxxx
Content-Type: application/json [ { "absoluteHeight": {
"lat": 49.288593,
"lon": -123.123453,
"base": 102.9
} } ]

Easy to Integrate

The location.io absolute height service is easy to integrate into any device or application. It includes a simple client library which automatically calibrates the onboard barometric pressure sensor. Altitude results are returned  in a WGS84 reference for quick and easy use within existing mapping solutions.