SAM-M10Q - Integration manual
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 AssistNow Offline data is encoded in a sequence of UBX-MGA-ANO messages, one
for every satellite for every day of the period covered. For example, data for all GPS satellites for 4
weeks will involve in excess of 900 separate messages, taking up around 70 kb which would not fit
into the available BBR memory in the receiver, and thus an external flash memory is required.
AssistNow Offline can also be used where the receiver has no flash storage. In this case, the host
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.
2.12.3.1 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.
The HTTP GET request from the client to the server should contain a standard HTTP query string in
the request URL. The query string consists of a set of "key=value" parameters in the following form:
key=value;key=value;key=value;
The following rules apply:
• The order of keys is not important.
• Keys and values are case-sensitive.
• Keys and values must be separated by an equals character ('=').
• Key-value pairs must be separated by semicolons (';').
• If a value contains a list, each item in the list must be separated by a comma (',').
The following table describes the keys that are supported.
Key name
Unit/range Necessity
Description
token
String
Mandatory The authorization token supplied by u-blox when a client registers to use the
service.
gnss
String
Mandatory A comma-separated list of the GNSS for which data should be returned. The
currently supported GNSS are: gps and glo.
period
Numeric
[weeks]
Optional
The number of weeks into the future the data should be valid for. Data can be
requested for up to 5 weeks into the future. If this value is not provided, the server
assumes a period of 4 weeks.
days
Numeric
[days]
Optional
The number of days into the future the data should be valid for. Can be used instead
of the period parameter when data for less than one week is desired.
resolution
Numeric
[days]
Optional
The resolution of the data: 1=every day, 2=every other day, 3=every third day. If this
value is not provided, the server assumes a resolution of 1 day.
Table 17: AssistNow Offline parameter keys
Thus, as an example, a valid parameter string would be:
token=XXXXXXXXXXXXXXXXXXXXXX;gnss=gps,glo;
2.12.3.2 Time, position and almanac
While AssistNow Offline can be used on its own, it is expected that the user will provide estimates of
the receiver's current position, the current time and ensure that a reasonably up-to-date almanac
UBX-22020019 - R01
2 Receiver functionality
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