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Axiom / Axiom Pro MFD cannot be configured to Head Up chart orientation
11-07-17, 09:21 AM
Post: #1
Axiom / Axiom Pro MFD cannot be configured to Head Up chart orientation
Axiom / Axiom Pro MFD cannot be configured to Head Up chart orientation

Two of the most commonly confused navigational terms are heading and course over ground (COG). Heading is the angular designation of the orientation of the vessel with respect to true or magnetic north ... in short, it is the direction in which the vessel is pointed. COG is the angular designation give to the direction in which the vessel is moving over the earth with respect to magnetic to true north. As indicated within this definition of COG, the vessel must be in motion to express the direction of its movement. Depending upon the vessel's speed and leeway (resultant of current and wind vectors), heading and COG may be very close or very different in value. Generally speaking, heading and COG will be closer in value as the speed of the vessel increases, thereby reducing the effects of leeway. Correspondingly, slower moving vessels will be more affected by leeway and as such slower moving vessels will typically display greater differences in the values reported for heading and COG.

Raymarine MFDs are not designed with an internal heading sensor. One may determine whether the Raymarine system has been interfaced to a source of heading data by configuring the MFD to display the "Heading" data item within the MFD's Databar, a Databox, or within one of the Data application's Data Panels. Should the reported value of "Heading" data item be ---, then one may assume that the Raymarine system has not been interfaced to a source of heading data.

GPS sensing devices are typically designed to function as source of heading data unless the product has been specifically designed, manufactured, and marketed as a GPS compass or has combined multiple sensors within a single device (ex. Airmar 220WX Weatherstation, Airmar GH2183, etc.). Accordingly, most GPS sensing devices are instead most commonly a source of COG data rather than heading data. Using the definition above, a stationary vessel (ex. one which is tied to a dock, mooring, etc.) has no COG. Additionally, when maneuvering or operating at very slow speeds, COG can be somewhat inaccurate due to update rates.

In systems lacking a source of heading data (ex. autopilot, instrument compass, GPS compass, etc.) where the vessel is stationary or operating below a speed that an accurate COG can be determined, the Chart application of an Axiom / Axiom Pro MFD operating with the latest available Raymarine product software updates will
- replace the vessel icon with a black dot, providing a visual cue that the system has no heading data or accurate COG to correctly orient a vessel icon.
- position the black dot (indicating the vessel's position) at the center of the Chart application's display
- orient the chart to North Up ... however, the orientation specified within the chart orientation listed within the titlebar will specify "(Head-Up)"
- changes to the Chart Orientation configuration setting (MENU->SETTINGS->VIEW & MOTION->CHART ORIENTATION) will be accepted, however the displayed chart will remain oriented North Up ... however, the orientation specified within the chart orientation listed within the titlebar will specify the selected chart orientation
- changes to the Boat Position configuration setting (MENU->PRESENTATION->VIEW & MOTION->BOAT POSITION) will be accepted, however, the black dot will continue to positioned within the middle of the displayed chart.

Once underway and making good way, the Chart application of the Axiom / Axiom Pro MFDs operating within a system not including a source of heading data will
- replace the black dot with a vessel icon oriented in the direction of COG
- orient the chart according to the Chart Orientation configuration setting
- offset the chart and vessel icon according to the Boat Position configuration setting
- the chart orientation specified within the Chart application will persist should the MFD be switched OFF and then switched ON.

Head-Up vs Course-UP Chart orientation ... Like the confusion over Heading and COG, many operators of systems lacking a Heading data source erroneously assume that the Chart application should be configured to Course-Up orientation rather than Head-Up orientation when seeking to have the system orient the chart in the direction in which the vessel is moving. Head-Up chart orientation is most commonly used by those operating in pilotage waters and/or to have all items displayed within the Chart application to be displayed relative to the vessel's head. In contrast Course-Up is associated with the the Chart application's navigation features (i.e. Go To Cursor/Waypoint and Follow Route). Should the system be commanded into navigation mode through execution of one of the aforementioned commands and should the Chart application then be commanded into Course-Up, then the displayed chart will be oriented to match that of the navigational course line to the waypoint/cursor position, which may or may not be the direction in which the vessel is moving over ground (COG) or pointed (heading).

It is not necessary to interface a heading data source to the system unless it is desired to have the vessel icon be properly oriented when the vessel is stationary or operating at maneuvering speeds or should one desire to utilize one of the system's heading dependent or heading enhanced features. Raymarine recommends that accurate 10Hz or greater heading data be supplied to any system using using any of (but not limited to) the following Radar and Chart application features:
- MARPA
- AIS Targets Displayed within the Radar Application
- Waypoints Displayed within the Radar Application
- North Up or Course Up orientation within the Radar Application
- Radar Overlay within the Chart Application .. may be used with COG alone.
- Heading Vector within the Chart Application
- Vessel Icon Orientation within the Chart Application (will default to COG when no heading data source is detected)
- Heading Databar and Data application data items
- Other features dependent on accurate, stable heading data.

It is generally recommended that Axiom / Axiom Pro MFDs consider installation of a Raymarine Evolution EV-1 CCU (Evolution Heading Sensor / Roll & Pitch Sensor / Rate of Turn Sensor / Course Computer) should it be desired to interface the MFD to a source of heading data. Not only is the EV-1 CCU designed to provide accurate and stable heading to the system, but may also form the basis of a future Evolution autopilot system. You will also find that the price of an EV-1 CCU is similar to that of other devices which simply sense heading.


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