ZED-F9P - Integration Manual
UBX-18010802 - R01
1 Overview
Page 10 of 64
Objective Specification - Confidential
This generated VRS data is then sent to the user through a wireless connection, often using the
Networked Transport of RTCM via Internet Protocol (NTRIP). Finally, just as if the VRS data had
come from a physical reference station, the rover receiver uses standard single-baseline algorithms
to determine the coordinates of the user’s receiver, in near-real-time kinematic or post-processed
modes. The main purpose of a VRS station is to reduce the baseline distance between the rover
and the reference station in order to efficiently remove spatially correlated errors using differential
processing, and to incorporate error corrections obtained from the reference stations network. The
Rover receiver must send its own actual position back typically using the NMEA GGA message.
Usually if the VRS system does not receive a GGA message it will not provide the RTCM3 data to the
Rover. he VRS concept allows a less dense antenna network without accuracy degradation because
the multiple reference station network better models the spatially correlated GNSS errors over
longer baselines. As a result the maximum distance between the rover and the nearest reference
station can be extended beyond the typical 10 ~15 kilometers without accuracy degradation of the
single reference station case. Another benefit of a VRS is that the reference data are free of site-
specific errors such as multipath, because the VRS computation assumes that the virtual station
is situated at an ideal location.
1.9 Configuration
The configuration settings can be modified using UBX protocol configuration messages, see the
Receiver Configuration and CFG Interface sections in the ZED-F9P Interface Description [
]. If
stored in RAM the modified settings remain effective until power-down or reset. If these settings
have been stored in BBR (Battery Backed RAM), then the modified configuration will be retained, as
long as the backup battery supply is not interrupted. The configuration can be saved permanently
in flash memory. The new messages that should be used are the UBX-CFG-VALSET, UBX-CFG-
VALGET, and UBX-CFG-VALDEL messages and are supported on the early Beta firmware. Please
see the u-blox ZED-F9P Interface Description [
u-center 18.05 or newer has support for the UBX-CFG-VALSET, UBX-CFG-VALGET and UBX-
CFG-VALDEL messages.
The early Beta firmware for the ZED-F9P still accepts the legacy UBX-CFG messages,
however these messages are now deprecated on ZED-F9P and have been replaced by new
configuration messages that should be used instead of the older UBX-CFG messages.
1.9.1 Communication interface configuration
It is possible to configure the communication interfaces of a base station or a rover. This is
done by setting the appropriate configuration items by using the UBX-CFG-VALSET message.
Several configuration items allow configuring the operation modes of the different communications
interfaces. This includes parameters for the data framing, transfer rate and protocols used. A
subset of the relevant configuration items is seen below for the UART1 only. For all for available
configuration items, see ZED-F9P Interface Description [
Configuration item
Description
CFG-UART1-BAUDRATE
The baud rate that should be configured on the UART1
CFG-UART1INPROT-UBX
Flag to indicate if UBX should be an input protocol on UART1
CFG-UART1INPROT-NMEA
Flag to indicate if NMEA should be an input protocol on UART1
CFG-UART1INPROT-RTCM3X
Flag to indicate if RTCM3X should be an input protocol on UART1
CFG-UART1OUTPROT-UBX
Flag to indicate if UBX should be an output protocol on UART1
CFG-UART1OUTPROT-NMEA
Flag to indicate if NMEA should be an output protocol on UART1
CFG-UART1OUTPROT-RTCM3X
Flag to indicate if RTCM3X should be an output protocol on UART1
Table 3: Typical configuration items used for UART1 baudrate and protocol configuration
