Lantronix PNT Series PNT-SG3FS GNSS Module Software User Guide - Page 44

5. Assisted GNSS Table 11. ST-AGNSS NMEA Interface Syntax $PSTMSTAGPSONOFF $PSTMSTAGPSINVALIDATE $PSTMGETAGPSSTATUS $PSTMSTAGPSSETCONSTMASK $PSTMAGPS $PSTMAGLO $PSTMPOLSTARTED $PSTMPOLSUSPENDED Description Turns ON/OFF the STAGPS\xaa engine Clears data stored in the STAGPS\xaa internal database Returns the status of the STAGPS\xaa internal processing Switches among the ST-AGNSS constellations Message with the same syntax as standard NMEA GSA Message Message with the same syntax as standard NMEA GSA Message Message in response to $PSTMSTAGPSONOFF Message in response to $PSTMSTAGPSONOFF Predictive AGNSS Predictive AGNSS, when used in systems with network data access, is able to provide fullconstellation long-term prediction taking advantage of an assistance server. Server based assistance for the TESEO™ III family of ST Microelectronics GNSS integrated circuits is done using location.io technology from RxNetworks. This unique solution combines the advantage of universal assistance data protocol with lightweight data access, by needing only about 9 KB biweekly data transfers to maintain fast and accurate GPS performance. Starting from this downloaded payload "seed", the ST-AGNSS is capable of generating at the client satellite orbit predictions for up to 14 days, with very high accuracy, for the complete GPS constellation and GLONASS constellation. The Assisted GNSS algorithm will seamlessly fall back from the14-day server-based prediction to 5-day autonomous prediction capability, which self-sustains on the field depending on usage patterns. This is very useful to keep quality of the GPS experience,should a connected device lose its ability to contact the server for coverage or roaming issues or any other wireless connectivity problem. While Autonomous AGNSS is completely transparent to the host device, the server-based (Predictive AGNSS) version should be downloaded from the server and passed to the GNSS device. The method to achieve the downloading is discussed in the following subsections. PGPS server should be accessed in the following ways: ♦ Host generates HTTP request string ♦ HTTP Request made from Host to RxNetworks ♦ Seed data packet returned to the Host ♦ Seed data sent to ST GNSS device ♦ ST GNSS device expands seed data into flash database ♦ Predicted ephemeris data available now and in future 14 days PGPS Server Access The HTTP Request URL To download a PGPS seed from the server, the application will need to format a HTTP request. Refer to the ST Microelectronics Application Note "AN5160: RxNetworks Assisted GNSS Server Interface Specification" to access the RxNetworksService. PNT-SG3FS GNSS Module Software User Guide 44