ZED-F9K - Integration manual
Key name
Unit/range Optional
Description
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 the
Position parameters (lat, lon,
section below). If this value is not provided, the server assumes an
accuracy of 300 km. Must be in range 0 to 6000000.
tacc
Numeric
[seconds]
Optional
Time parameters (tacc and latency)
section 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 18: 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
3.7.4.4.1 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 satellites 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 100 km 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, the user will
experience prolonged or even failed startups.
3.7.4.4.2 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 10 ms but by default the time accuracy is indicated to be +/-10
seconds in order to account for network latency and any time between the client receiving the data
and it being provided to the receiver.
UBX-20046189 - R01
3 Receiver functionality
Page 51 of 105
C1-Public
Early production information
