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Radar overlay is not properly aligned with cartography
04-13-16, 09:33 AM (This post was last modified: 04-10-18 08:02 AM by Chuck - Raymarine - Moderator.)
Post: #1
Radar overlay is not properly aligned with cartography
Radar overlay is not properly aligned with cartography

Proper operation of the Chart application's Radar Overlay feature is dependent upon proper configuration and operation of each of the following:
- GPS ... check for low HDOP (HOME->SET-UP->SYSTEM SETTINGS->GPS SET-UP->VIEW SATELLITE STATUS). A GPS having a good position FIX will generally have a HDOP value of 1.0 or less. If a high HDOP is reported using the MFD's internal GPS sensor and should the MFD's installation location not afford it an unobstructed view of the skies overhead, then the system should be fitted with an external GPS sensor (ex. Raystar 130 GPS Sensor, GA150 GPS Antenna, etc.).

- Radar Scanner Ships Heading Sensor ... open the Radar application page and configure it for Head Up orientation. Verify that radar returns are being properly plotted (i.e. check relative bearings) with respect to the vessel's head. If not, then the Radar Bearing Alignment feature (MENU->RADAR SET-UP->ADVANCED->BEARING ALIGNMENT) should be adjusted such that radar returns are being properly plotted with respect to the vessel's head. Should bearing alignment adjustments not permit radar returns to be properly plotted radar with respect to the vessel's head, then the radome or open array pedestal should be sent to Raymarine’s Product Repair Center to be bench tested / serviced.

GPS COG vs Heading ... Should an a/c/e/eS/gS-Series MFD be operating with the latest available software update, then it will support the Chart application's Radar Overlay feature without heading input when GPS COG data is available within the system. However, there are limitations to COG's ability to function as a substitute for heading data (i.e. when the vessel is stationary or maneuvering at slow speed, or under the influence of leeway (current or wind), then COG may not be representative of the vessel's heading). Should you desire to use the MFD's MARPA radar features, then a heading sensor supporting 10Hz or greate heading data updates would be recommended (ex. Raymarine EV-1 Sensor Core, Airmar H2183, KVH AutoComp 1000, etc.). The principal advantage of the EV-1 Sensor Core is superior heading performance and a single point of contact for support associated with the MFD and/or the heading sensor.

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).

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:

--- Doppler assisted automatic target acquisition (MFDs running LH3 software equipped w/Quantum 2 Radomes)
--- AIS Targets Displayed within the Radar Application
--- Waypoints Displayed within the Radar Application
--- North Up or Course Up orientiation 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 heading dependent features.

- Heading ... Incorrect heading data it the most common cause for misalignment of of radar overlaying the Chart application. The MFD should be configured to display the Heading data item within its Databar, Databox, or Data application panel. The vessel should then be steered at each of the intercardinal (or better yet half wind point of the compass) compared to the vessel's properly calibrated fluid filled compass (if so equipped). Should heading errors be detected, then the vessel's heading data source will need to be recalibrated for deviation and then aligned to the correct heading. The owner's manual for the heading data source should be consulted for information concerning how to calibrate it for deviation and then align the compass. After doing so, then the heading should be tested against vessel's properly calibrated fluid filled compass (if so equipped) again. Should heading error continue to be detected then it is recommended that the heading data sensing device be serviced.

Before performing any calibration and alignment of a heading sensor, it is strongly recommended that the area around the heading sensor be inspected to ensure that all sources of magnetism (ex. ferrous materials, electric motors, high current carrying conductor have not been located within at least 3' of the heading sensor. Please click here to view a FAQ addressing this subject. The most common source of heading data onboard a vessel is an autopilot system. Other heading sources include the retired ST60+ Instrument Compass, Pathfinder Smart Heading System, and third party NMEA 0183 and NMEA 2000 GPS Compasses and magnetic heading sensors.

- Cartography ... should the cartography being overlaid feature a georeferencing error, the cartography may not only have an offset error, but may also have an orientation error. Cartography georeferencing error are most commonly detected when the user observes that the vessel icon's plotted position is not consistent with the vessel's actual position. When electronic cartography was in its infancy, cartography georeferencing errors were quite common, but are less common today. Cartography georeferencing errors should be reported to the cartography manufacturer.

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