ZOE-M8B - System Integration Manual
UBX-17045131 - R04
Contents
Page 32 of 42
Production Information
u-blox only sends ephemeris data for those satellites currently visible to the mobile device requesting
the data, thus minimizing the amount of data transferred.
The AssistNow Online service provides data for GPS, GLONASS, BeiDou, Galileo and QZSS.
3.2.2
AssistNow™ Offline (ANO)
With AssistNow Offline (ANO), users can download long-term orbit data from the Internet at their
convenience. The orbit data can be stored in the u-blox M8 GNSS receiver’s external SQI flash memory
(if available) or in the memory of the application processor. Thus, the function requires no connectivity
at system start-up and enables the GNSS performance and power consumption improvement even
when no network is available.
The long term-orbit data is based on differential almanac correction data. Because this system
utilizes the almanac data on the receiver, the current almanac should be also available.
Almanac data can be loaded separately or alongside with the ANO data.
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AssistNow Offline offers augmentation for up to 35 days.
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AssistNow Offline service provides data for GPS and GLONASS only; BeiDou and Galileo are not
currently supported.
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AssistNow Offline cannot be used at the same time with AssistNow Autonomous.
3.2.3
AssistNow™ Autonomous
AssistNow Autonomous provides aiding information without the need for any external network
connection. It is based on broadcast satellite ephemeris data that the receiver has previously
downloaded. AssistNow Autonomous automatically generates accurate predictions of satellite
orbital data (“AssistNow Autonomous data”) that is usable for future GNSS position fixes. The
concept capitalizes on the periodic nature of GNSS satellites: their position in the sky is repeated
every 24 hours. By capturing strategic ephemeris data at specific times of the day, the receiver can
predict accurate satellite ephemeris for up to six days after initial reception. The use of an SQI flash
memory is recommended when using AssistNow Autonomous, otherwise only GPS satellites are used
and the prediction time decreases to three days.
u-blox’s AssistNow Autonomous benefits are:
•
No connectivity required
•
Can work stand-alone or concurrently with AssistNow Online
•
No integration effort; calculations are done in the background, operation is transparent to the user
3.3
Data Batching
The data batching feature allows position fixes to be stored in the RAM of the receiver to be retrieved
later in one batch. Batching of position fixes happens independently of the host system, and can
continue while the host is powered down.
The RAM available in the chip limits the size of the buffer. With the default 1 Hz navigation rate, up to
five minutes of data can be stored to the buffer. To make the best use of the available space, only a
minimum set of data is stored for each navigation epoch by default. More detailed information can be
stored on the position fixes; however, this reduces the number of fixes that can be batched.
It is possible that the host is not able to retrieve the batched fixes before the buffer fills up. In such
cases, the oldest fix will be dropped and replaced with the newest. The host can request batching
status information to see if fixes have been dropped.
