General information: When two GNSS antennas are connected to the iCG82 instrument and have a clear view of the sky, the instrument automatically provides a precise GNSS
heading relative to True North.
☞ ORP outputs heading relative to grid north instead of true north when a local grid coordinate system is used. The HDT, VTG, XDR messages will always be relative to true north as defined in NMEA-0183 standard.
The iCG82 uses a Advanced SmartHeading method of calculating the precise position of the secondary GNSS antenna. This means that precise heading output is available even when the instrument is not receiving corrections from a base station.
The antenna connected to port ANT1 is always the primary GNSS antenna while the one on port ANT2 is always the secondary (heading) GNSS antenna.
Mounting of GNSS antennas: For best results, it is recommended to mount the two GNSS antennas according to following guidelines
• separated as far as possible,
• at approximately the same height,
• with the TNC connectors orientated in approximately the same direction, and
• ensuring an unobstructed view of the sky.
Heading Adjustment: Heading output is the azimuth from GNSS Antenna 1 to GNSS Antenna 2. If it is not possible to mount the antennas parallel to the centreline of the vehicle,
then the known orientation to the centreline can be entered as a Heading Adjustment.
The Heading Adjustment field offers the opportunity to enter an angle correction in order for the heading to be calculated in the exact direction of the machine.
It is important to note that:
• The Heading is the vector from Antenna 1 to Antenna 2 in degrees clockwise from north rather than clockwise from the vehicle reference frame.
• The Heading Adjustment is always applied from a bird’s eye view perspective.
• A positive Heading Adjustment is applied clockwise from North while a negative Heading Adjustment is applied anticlockwise from North.
Heading output: Heading information is available in the Position sub menu on the display.
Heading output can be configured on either of the serial ports (P1 or P2) using the NMEA Output wizard.
Heading output is available in following message formats:
• Leica ORP
• NMEA HDT
• NMEA VTG
• NMEA XDR
Refer to 6.3 ORP and NMEA Output for further information.