ZED-F9P-Integration Manual
UBX-18010802 - R02
4 Receiver description Page 42 of 114
Advance Information
Key Name Unit/
Range
Optional Description
gnss String Mandatory A comma separated list of the GNSS for which data should be returned. Valid
GNSS are: gps, qzss and glo.
datatype String Mandatory A comma separated list of the data types required by the client. Valid data types
are: eph, alm, aux and pos. Time data is always returned for each request. If the
value of this parameter is an empty string, only time data will be returned.
lat Numeric
[degrees]
Optional Approximate user latitude in WGS 84 expressed in degrees and fractional degrees.
Must be in range -90 to 90. Example: lat=47.2.
lon Numeric
[degrees]
Optional Approximate user longitude in WGS 84 expressed in degrees and fractional
degrees. Must be in range -180 to 180. Example: lon=8.55.
alt Numeric
[meters]
Optional Approximate user altitude above WGS 84 Ellipsoid. If this value is not provided, the
server assumes an altitude of 0 meters. Must be in range -1000 to 50000.
pacc Numeric
[meters]
Optional Approximate accuracy of submitted position (see position parameters note below).
If this value is not provided, the server assumes an accuracy of 300km. Must be in
range 0 to 6000000.
tacc Numeric
[seconds]
Optional The timing accuracy (see time parameters note below). If this value is not
provided, the server assumes an accuracy of 10 seconds. Must be in range 0 to
3600.
latency Numeric
[seconds]
Optional Typical latency between the time the server receives the request, and the time
when the assistance data arrives at the u-blox receiver. The server can use
this value to correct the time being transmitted to the client. If this value is not
provided, the server assumes a latency of 0. Must be in range 0 to 3600.
filteronpos (no value
required)
Optional If present, the ephemeris data returned to the client will only contain data for the
satellites which are likely to be visible from the approximate position provided by
the lat, lon, alt and pacc parameters. If the lat and lon parameters are not provided
the service will return an error.
filteronsv String Optional A comma separated list of u-blox gnssId:svId pairs. The ephemeris data returned
to the client will only contain data for the listed satellites.
Table 15: AssistNow Online Parameter Keys
Thus, as an example, a valid parameter string would be:
token=XXXXXXXXXXXXXXXXXXXXXX;gnss=gps,qzss;datatype=eph,pos,aux;lat=47.28;lon=8.56;pacc=1000
4.6.6.1 Position parameters (lat, lon, alt and pacc)
The position parameters (lat, lon, alt and pacc) are used by the server for two purposes:
• If the filteronpos parameter is provided, the server determines the currently visible satellites at
the user position, and only sends the ephemeris data of those satellites which should be in view
at the location of the user. This reduces bandwidth requirements. In this case the "pacc" value
is taken into account, meaning that the server will return all SVs visible in the given uncertainty
region.
• If the datatype "pos" is requested, the server will return the position and accuracy in the response
data. When this data is supplied to the u-blox receiver, depending on the accuracy of the provided
data, the receiver can then choose to select a better startup strategy. For example, if the position
is accurate to 100km or better, the u-blox receiver will choose to go for a more optimistic startup
strategy. This will result in quicker startup time. The receiver will decide which strategy to choose,
depending on the "pacc" parameter. If the submitted user position is less accurate than what is
being specified with the "pacc" parameter, then the user will experience prolonged or even failed
startups.
4.6.6.2 Time parameters (tacc and latency)
Time data is always returned with each request. The time data refers to the time at which the
response leaves the server, corrected by an optional latency value.This time data provided by the
service is accurate to approximately 10ms but by default the time accuracy is indicated to be +/-10
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