Technology
Self-ephemeris™

The GPS/GNSS receiver uses the orbital information of the target satellite (ephemeris data) to calculate its own position. If the GPS/GNSS receiver already has a backup of valid ephemeris data stored, it will quickly (within a few seconds) calculate its position after powering on (known as a hot start). However, if there are no valid backup ephemeris data, or if the backup data have expired, it must receive the navigational information from the transmitting satellite, or access the assisted GNSS server via the internet (known as a warm start). It takes roughly 18 to 30 seconds to extract the ephemeris data from the satellite navigational information, and therefore roughly 35 seconds before a position is calculated. If the GPS/GNSS receiver is connected to a network and able to get the satellite orbital information from the assisted GNSS server, it can get the required information faster than it can from a satellite, but will still need time to transmit the data. Therefore, a warm start requires more time than a hot start.

The active ephemeris validity period is usually 4 hours, and, if exceed, the ephemeris data must be refreshed. Accordingly, the GPS/GNSS receiver can quickly calculate its position from the new ephemeris data (hot start) only for a maximum period of 4 hours. Devices with onboard GPS installed (for example a car navigation system), normally need to re-calculate their position if turned off for more than 4 hours, and require time to do so (warm start). Self-Ephemeris™ solves this problem by allowing for a startup that is equivalent to a hot start for up to 72 hours. This is performed independently by the GPS/GNSS receiver, and can function without a network connection or a connection to an assisted GNSS server.

Self-Ephemeris™ technology uses a specialized algorithm to predict and estimate the orbital information of a satellite based on previously received ephemeris data, and allows the GPS/GNSS receiver to have a TTFF in the same amount of time as a hot start, for up 72 hours.

With Self-Ephemeris™, every time the GPS receives new ephemeris data, the internal receiver automatically recalculates the data as required, for operation that requires minimal user interference.