General information: When two iCG120 instruments are used 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 iCG120 uses an Advanced SmartHeading method of calculating the precise position of the secondary iCG120. This means that precise heading output is available even when the instrument is not receiving corrections from a base station.
The primary iCG120 and the secondary (heading) iCG120 are selected in MC1.
Mounting of GNSS antennas
For best results, it is recommended to mount the two iCG120 instruments according to following guidelines:
• separated as far as possible,
• at approximately the same height,
• with the 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 via the iCON gps 120 Web Interface. Refer to: Home
Heading output can be configured on the Configuration page. Refer to: Sensor Configuration
Heading output is available in following message formats:
• Leica ORP
• NMEA HDT
• NMEA VTG
• NMEA XDR
Refer to NMEA Message Formats for further information.