Yo All! An update on my playing with the NEO-M9V receiver from u-blox. One feature is the inclusion of a lifetim AssistNow account. The sole purpose of A-GNSS products, like AssistNow is to improve TTFF. Since I tend to leave my GNSS receivers on forever, the feature has not been of much interst to. I grant that for battery saving, the option to quickly gather a fix, and then sleep is valuable to some.
Note that AssistNow should not be confused with some of their other assistance products, like Point Perfect. Here is a simple test using the u-blox sample code: assistnow_example_v1.1.1.py Get is from their Getting Started guide here: https://support.thingstream.io/hc/en-gb/articles/20837860069788-AssistNow-Getting-Started-Guide The python tool automates the handling of the A-GNSS data, and could be simply run before starting gpsd. First I use the tool to measure TTFF from a cold start: ~ # python assistnow_example_v1.1.1.py -P /dev/ttyACM1 -z <redacted> -n Polling UBX-SEC-UNIQID from receiver UBX-SEC-UNIQID: 21425a521b5e Polling UBX-MON-VER from receiver UBX-MON-VER: EXT CORE 1.00 (add159) 00190000 ROM BASE 0x118B2060 FWVER=MDR 2.16 PROTVER=35.16 MOD=NEO-M9V GPS;GLO;GAL;BDS SBAS;QZSS Resetting the receiver to simulate a cold start Waiting for receiver to be ready after reset... Waiting for UBX-NAV-STATUS to report time to first fix... Time from reset to first fix (TTFF): 35518 ms 35 seconds. A tad higher than I expected, but acceptable. So now I use Assit Now to see how fast TTF can be: ~ # python assistnow_example_v1.1.1.py -P /dev/ttyACM1 -z <redacted> -l Polling UBX-SEC-UNIQID from receiver UBX-SEC-UNIQID: 21425a521b5e Polling UBX-MON-VER from receiver UBX-MON-VER: EXT CORE 1.00 (add159) 00190000 ROM BASE 0x118B2060 FWVER=MDR 2.16 PROTVER=35.16 MOD=NEO-M9V GPS;GLO;GAL;BDS SBAS;QZSS Sending ZTP request to obtain chipcode with payload: { "token": "b1f9293a-e5a9-46e2-946f-d981fbc37852", "messages": { "UBX-SEC-UNIQID": "b562270309000100000021425a521b5e05", "UBX-MON-VER": "b5620a04dc0045585420434f524520312e3030202861646431353929000000000000000030303139303030300000524f4d20424153452030783131384232303630000000000000000000000046575645523d4d445220322e31360000000000000000000000000000000050524f545645523d33352e313600000000000000000000000000000000004d4f443d4e454f2d4d3956000000000000000000000000000000000000004750533b474c4f3b47414c3b424453000000000000000000000000000000534241533b515a53530000000000000000000000000000000000000000003f56" } } Received ZTP response with authorization chipcode Available data types for this device: ualm, uporb_1, uporb_3, uporb_7, uporb_14, ulorb_l1, utime, ukion, usvht Requesting live orbits and almanac data: ulorb_l1,ukion,usvht,ualm https://assistnow.services.u-blox.com/GetAssistNowData.ashx AssistNow data received successfully Resetting the receiver to simulate a cold start Waiting for receiver to be ready after reset... Enabling CFG-NAVSPG-ACKAIDING Sending 13856 bytes of AssistNow messages to the receiver... Warning: Resending 36 unacknowledged messages (try 2) All 228 MGA messages acknowledged. Waiting for UBX-NAV-STATUS to report time to first fix... Time to inject AssistNow data: 5289 ms Time from reset to first fix (TTFF): 42394 ms Wow. I did not expect that. TTFF is 7 seconds slower. The time spent downloading the assistance data just added to the TTFF... Oh well... RGDS GARY --------------------------------------------------------------------------- Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703 [email protected] Tel:+1 541 382 8588 Veritas liberabit vos. -- Quid est veritas? "If you can't measure it, you can't improve it." - Lord Kelvin
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