NEO-M9N - Integration manual
•
Save-on-shutdown:
The receiver can be instructed to dump its current state to flash memory
as part of the shutdown procedure; this data is then automatically retrieved when the receiver
is restarted. For more information, see section
. For information on
the UBX-UPD-SOS messages consult the applicable interface description [
].
•
Database dump:
The receiver can be made to dump the state of its navigation database in the
form of a sequence of UBX messages reported to the host; these messages can be stored by
the host and then sent back to the receiver when it has been restarted. See the description of
the UBX-MGA-DBD messages in the applicable interface description [
]for more information.
3.9.3 AssistNow Offline
AssistNow Offline is a feature that combines special firmware in u-blox receivers and a proprietary
service run by u-blox. It is targeted at receivers that only have occasional internet access and so
cannot use AssistNow Online. AssistNow Offline speeds up time to first fix (TTFF), typically to
considerably less than 10 s.
AssistNow Offline currently supports GPS and GLONASS. u-blox intends to expand the
AssistNow Offline Service to support other GNSS (such as BeiDou and Galileo) in due course.
The AssistNow Offline Service uses a simple, stateless, HTTP interface. Therefore, it works on all
standard mobile communication networks that support internet access, including GPRS, UMTS and
Wireless LAN. No special arrangements need to be made with mobile network operators to enable
AssistNow Offline.
Users of AssistNow Offline are expected to download data from the AssistNow Offline Service,
specifying the time period they want covered (1 day to 5 weeks) and the types of GNSS. This data
must be uploaded to a u-blox receiver, so that it can estimate the positions of the satellites, when no
better data is available. Using these estimates will not provide as accurate a position fix as if current
ephemeris data is used, but it will allow much faster TTFFs in nearly all cases.
The data obtained from the AssistNow Offline Service is organized by date, normally a day at a
time. Consequently the longer time for which coverage is requested, the larger the amount of data
to handle. Similarly, each different GNSS requires its own data and in the extreme cases, several
hundred kilobytes of data will be provided by the service. This amount can be reduced by requesting
lower resolution, but this will have a small negative impact on both position accuracy and TTFF. See
the section on
for details of how to specify these options.
The downloaded Offline data is encoded in a sequence of UBX-MGA-ANO messages, one for every
SV for every day of the period covered. Thus, for example, data for all GPS SVs for 4 weeks will involve
in excess of 900 separate messages, taking up around 70 Kbytes. Where a u-blox receiver has flash
storage, all the data can be directly uploaded to be stored in the flash until it is needed. In this case,
the receiver will automatically select the most appropriate data to use at any time. See the section
on
AssistNow Offline can also be used where the receiver has no flash storage, or there is insufficient
spare flash memory. In this case the customer's system must store the AssistNow Offline data until
the receiver needs it and then upload only the appropriate part for immediate use. See the section
on
for further details.
3.9.3.1 Service parameters
The information exchange with the AssistNow Offline Service is based on the HTTP protocol. Upon
reception of an HTTP GET request, the server will respond with the required messages in binary
format or with an error string in text format. After delivery of all data, the server will terminate the
connection.
UBX-19014286 - R07
3 Receiver functionality
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