CPT7 and CPT7700 Installation and Operation User Manual v12
109
Chapter 5 CPT7 with Dual Antenna
NovAtel's ALIGN heading technology generates a heading solution using the position information from the
primary and secondary GNSS antenna. The CPT7700 requires a second receiver to generate an ALIGN
solution. The CPT7 can provide an ALIGN solution without an additional receiver.
With SPAN, the ALIGN GNSS baseline can be used to assist the initial alignment of the SPAN solution. In
addition, the ALIGN baseline solution will aid the heading solution from the receiver if the heading drifts due to
slow or constant dynamics.
ALIGN is capable of a 10 Hz heading output rate.
For optimal SPAN performance when using Dual Antenna with SPAN an ALIGN offset calibration is
required for each unique installation. This calibration refines the IMU to antenna baseline angular
offset from the initial estimate derived from the input lever arms. Refer to
INSCALIBRATE
command
for details.
5.1 Installation
The hardware for SPAN with Dual Antenna is installed in a manner similar to other SPAN systems. Some
points to consider during your installation are:
1. Install the CPT7 and the two antennas in the vehicle such that the relative distance between them is fixed.
2. The antennas should be mounted as a similar height, relative to the CPT7, where the view of the satellites
will not be obstructed by any part of the vehicle. As heading accuracy is dependent on baseline length,
mount the antennas as far apart as possible. A minimum separation distance of 1 meter is recommended.
3. The lever arms or distance from the CPT7 to the antennas needs to be fixed and accurately measured
using the coordinate axes defined on the outside of the CPT7. The baseline between the two antennas
does NOT need to be aligned with the vehicle axes or with the axes of the CPT7.
4. If using a CPT7700, the CPT7700 and the second receiver need to be powered and connected to each
other via COM 2 before sending any configuration commands. It does not matter which receiver is
powered on first, or how long they are both powered before sending any commands.
SPAN with Dual Antenna operation assumes the use of the COM 2 port for communication between
receivers unless a different port is specified using the
INSALIGNCONFIG
command. This command
can change the COM ports of the SPAN-enabled master and the rover, the baud rate used and data
output rates.
For information about connecting the ALIGN master and rover receivers using a port that is not a
serial COM port (e.g. Ethernet), contact NovAtel Customer Support.
For a CPT7700, the two receivers need to be set up as shown in the example in
The CPT7 contains the hardware necessary to provide an ALIGN solution without an additional receiver. Set
up a SPAN system with a dual antenna receiver as shown in