[CA] [CA11] Axiom Pro RVX Course Up Issues.

[PetrelMarine]

Hi Chuck

Can you please help me with an issue I am having with a newly installed Axiom 16" PRO RVX. This unit was installed replacing an E140W, integrating it as far as possible with the original equipment installed. I have attached a layout of the system. The issue I am having is as follows.

i. Chart behaves erratically in Course Up. I have tried every possible configuration but when the 16" display is placed in Course Up orientation, the chart does not orientate to display the course to the noon position. I've tried so many different motion and presentation settings to try and get the unit to behave normally and still cannot get it to. I have not seen this behavior with other Axiom units, it's utterly confusing and defies any logic whatsoever when underway.

ii. The COG as displayed by the unit 16" whilst using the internal GPS, which is set as the manual selected GPS, can sometimes be significantly off from reality. I have checked it against another independent GPS and manual compass, and have sometimes seen it differ up to 30 degrees with no tide/drift conditions . Again, totally odd behavior.

All other equipment and operations work just fine except for this issue and I am completely at a loss as to what to do next.
Thanks.

Matt

[Chuck - Raymarine - Moderator]

Welcome back to the Raymarine Forum Matt,

Please click here to view the FAQ addressing the differences between Head Up and Course Up chart orientations. Should navigation (i.e. Go To Waypoint / Cursor Position or Follow Route) not have been commanded within the system, then the chart orientation should be configured to either Head Up or North Up. Course Up orientation has no application within a system in which navigation has not been commanded. Should the problem occur when navigation has been commanded, then please respond accordingly.

[PetrelMarine]

Thanks for your help and that clarification. We will run more tests this week and try using HEAD UP although we had tried that before also and seen similar odd behavior. But we will try again to confirm.

To follow up on my original post, can you please suggest why the COG as reported by the Axiom 16" RVX is different from other onboard independent COG readings. With the vessel underway at 20kts+ on a stable course, an unconnected and independent GPS COG is as much as 20 degrees off from the Axiom COG.

We checked the independent COG against actual vessel heading in no drift conditions and they matched within a degree or two, however the Axiom was again about 20 degrees off. Again, all readings are in degrees Magnetic.
So it seems like the Axiom COG is off from other sources which appear to be correct, and the Axiom incorrect.
Thanks for your help and patience if I am missing something obvious.

[Chuck - Raymarine - Moderator]

PetrelMarine,

COG differences may result from:

- a software issue within the MFD / system components ... ensure that all Raymarine products as well as third party products have been updated with the latest available Raymarine product software updates. Please additionally ensure that a Power On Factory Reset operation has been performed to the system's MFD and that afterwards, all configuration settings have been manually reconfigured rather than from a saved settings file.

- not having used the Data Sources feature to have manually designated the GPS data source for the system within a system featuring more than one source of GPS data. The GPS source having the most unobstructed view of the skies overhead should be selected.

- poor GPS signal reception ... please click here to view a FAQ addressing this subject.

- use of different and/or incorrect magnetic variation values within the MFD or compared systems ... check the settings within each product to ensure that they have all be configured with the same magnetic variation value,

- an installation issue ... should the above listed items not have addressed the issue, then attach a diagram of the system identifying each of the items within the system and how they have been interfaced to one another. Please additionally attach the System Information diagnostics file from the system's Data Master MFD.

[PetrelMarine]

Hi Chuck

So I performed the factory hard reset last week and also disconnected the NMEA2000 network. This left the internal GPS as the only position source for the Axiom 16RVX. The only other items left connected were the radar and external sounder module as shown in the diagram that I sent originally in the first post.

The unit continues to report completely erroneous CoG readings, with completely inaccurate radar to chart overlay as a result. The vessel was on one occasion shown in the incorrect location and then froze on another occasion. The GPS reception was checked and multiple satellites were available and being used, accuracy supposedly approximately less than 3ft.

The CoG was checked against a smaller Axiom 7" which was isolated from the Axiom 16RVX but connected to the N2K network, nothing else. It's behavior was normal and CoG values made sense as cross referenced to another independent CoG and also heading (No Drift Conditions). So the fault seems to be associated with the Axiom 16" or potentially it's network? Why the network would cause this behavior I don't know.

I'm at a loss and I really need your help.
Thank you.

Matt

[Chuck - Raymarine - Moderator]

Matt,

While I understand your desire to remove possible sources of the problem reported, the DSM would have no bearing and as such need not be disconnected from the system. Per our discussion, both the Axiom Pro MFD and Axiom MFD are reporting HDOP values of 0.8 when operated independently. The resulting GPS performance should be identical. However, as you have indicated, the COG is significantly greater. Per our conversation ... and not indicated within your diagram, the Axiom Pro MFD has been interfaced to a VHF radio throughout this investigation, which is by your recollection, an Icom VHF radio. As indicated, we have had some past experience with Icom VHF radios looping received NMEA 0183 data. The problem with such is that if the MFD has been interfaced in a manner which would support bidirectional communications with a device which is looping NMEA 0183, the MFD will perceive it to be an additional NMEA 0183 source of GPS data ... and by LH3 prioritization schema, assign it highest priority. This may have the added effect of causing the apparent doubling of the local magnetic variation applied to COG. In the Seattle area, the local magnetic variation is approximately 15.5 degrees. The suggested data loop may result in approximately 31 degrees of local magnetic variation being applied instead of 15.5 degrees. Accordingly, I suggest that the BAUD rate setting of the Axiom Pro MFD's NMEA 0183 Port which has been interfaced to the VHF radio be changed from a matching BAUD rate (typically 4800 for DSC VHF radios lacking AIS features) to a mismatched BAUD rate (i.e. 38400), thereby breaking communications between the MFD and VHF radio, and that the system then be tested again. I further recommend that the Mercury Marine devices be disconnected during this test. Should the system perform correctly after having made the specified changes, then BAUD rate of the Axiom Pro MFD's NMEA 0183 Port may be changed back to its original setting and the system tested ... I suspect that you may find that the symptom returns. If not, then the Mercury Marine devices may be reconnected and tested one by one to determine whether either causes the reported issue.

Should the problem be determined to be solely attributed to the VHF radio, then the following two options would apply:
a) disconnect the MFD's NMEA 0183 input leads from the VHF radio's NMEA 0183 output leads; or
b) install a programmable NMEA 0183 multiplexer (ex. Actisense NDC-4-USB, etc.) between the MFD's NMEA 0183 input leads from the VHF radio's NMEA 0183 output leads. The NMEA 0183 multiplexer would then be programmed to only pass the DSC and DSE NMEA 0183 sentences to the MFD.

[PetrelMarine]

Hi Chuck

Thanks for your help today and your detailed feedback. I was unaware that the ICOM VHF behaved like that. Tonight I connected an 0183-USB converter to the VHF output and watched the data and can confirm that data is being looped back from the Axiom 16.

So when the data source is selected as the internal GPS on the Axiom 16, what happens when the VHF is turned on is the GPS status page indicates that 0183 is being used. I can't remember the exact wording but its something like " NMEA 0183 (5) to NMEA 0183 (1)". So you are absolutely correct, the VHF is looping the internal GPS data it's receiving and then the Axiom is re-using this GPS data when it is transmitted back. I can imagine that would cause all sorts of issues so this may be the problem, I am hoping it is. Your theory on the double application of the local variation/declination seems logical and hopefully that clears up with this also.

We will be testing the system again tomorrow, only this time with the VHF 0183 output disconnected. I will report back on how things go.
Thank you again for all your help sir.

Matt

[Chuck - Raymarine - Moderator]

You're welcome.