Troubleshooting - Sure-Path GPS Boat Lane Tracking

Boat Lane Tracking
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Data Communications
If the rover phone is stuck in "GPS" mode and will not achieve "DGPS", "RTK Float" or "RTK Fix" then this means that error signals from the Base are not being received by the Rover.

To find out where the problem is, you must be methodical and follow the path the data takes going from Base to Rover. Do the following in this order:

On the Base phone:
    • Check that the upper progress bar is animating. This shows that data is being received via bluetooth from the base receiver. If not, then either there is no bluetooth connection between the base receiver and the phone or the receiver is not seeing any satellites, ie there is a problem with the antenna or its connection.
    • If the upper progress bar is animating, check that the lower progress bar is also animating. This normally shows that data is successfully being sent to the cloud server. If not, then one of the following could be the cause:
        • The base phone has no internet access. This could be because:
        • There is no WiFi or SIM card installed to enable the phone to have internet access.
          • If there is a SIM card, check that:
            • You have a decent cell signal.
            • Mobile Data is turned on (in the phone's "Settings\Mobile network").
            • The phone's APN settings are correct for your network carrier.
            • You haven't run out of credit!
          • If you are using WiFi, check that:
            • You are still within range of the WiFi
            • The router feeding your WiFi network is still OK and is providing internet access. You can do this by using a browser on a different phone or device on the same WiFi to check whether it has internet access.
        • The Base Phone Mountpoint and/or Password settings are wrong or missing. These are normally pre-configured for you but if you suspect this is a problem, contact us for the correct settings.

If you are seeing both progress bars animating, then all is well with the Base receiver and phone and you can move on to checking the Rover.

On the Rover phone:
    • Check that the Mountpoint and Password are set the same as for the Base.
    • Assuming the Rover is using 3/4G for its internet access, do the same checks as for the Base phone:
      • You have a decent cell signal
      • Mobile Data is turned on.
      • The phone's APN settings are correct for your network carrier.
      • You haven't run out of credit!

If the Status on the Rover phone (displayed just below the Connect button) is "DGPS", "RTK Float" or "RTK Fix", then the data link from Base to Rover is fine. If you are only reaching "DGPS" or "RTK Float" and not "RTK Fix", it is not because of the data link. Instead it is to do with the quality/strength of the GPS signals. See the next section.

GPS Signal Quality
If the Rover reaches "DGPS" or "RTK Float" but is unable to reach "RTK Fix" status (or "RTK Fix" is unreliable), then the quality of the GPS signal at the Base and/or the Rover needs to be improved.

Base Antenna
We cannot stress enough that if you can get the Base antenna position to be the best it can be, then it is much easier for the Rover to make do with moderate GPS signals and still reach "RTK Fix".

In an ideal world, the base antenna should have clear view of the sky all the way down to about 15⁰ above the horizon in ALL directions. This maximises the number of good satellites that can be used for generating the error data signals the Rover needs to achieve RTK Fix. Also, the antenna should be away from any hard vertical surfaces such as walls of buildings which can give rise to reflected GPS signals which confuse the receivers.

To achieve the above, you may need to mount the antenna high up on a roof or pole so that it is not overlooked by tall trees or buildings. You can run a coax extension to the antenna if it is impractical to have the receiver box and phone close to the antenna. Certainly 30 metre (50') extensions have been tested and you could probably go to 60 metres (100') if required. We would recommend RG58 coax cable for extensions over 3 metres (as opposed to the thinner RG174). When looking for an extension cable, it needs to be SMA-male to SMA-female. Do NOT get anything that has "RP" in the name of the connector such as "RP-SMA-male" as these are "reverse polarity".

Rover Antenna
At the Rover, you are obviously limited to where the antenna can go in the boat but things to be aware of are:

    • If the boat is near a bank with tall trees then they will reduce the GPS signals.
    • If the antenna is mounted too low on the pylon, then you are reducing the antenna's view of the sky.
    • If you are under any sort of roof (eg your jetty canopy), then it will severely restrict GPS signals. When the boat moves out onto open water, it will usually be fine again.
    • The bimini on your boat has very little effect on the GPS. This is because RF signals (such as GPS) are primarily absorbed and stopped by moisture. Trees contain a lot of moisture and therefore are not good. Your bimini hopefully contains zero water and so is fine.

If you find that despite the Base antenna having a very good position, the Rover status is still not reliably in "RTK Fix", then you can upgrade the standard UBlox boat antenna to a survey grade antenna, (the same as is used for the Base). We are also experimenting with another style of antenna (a helical design) which is extremely light and compact and may give better results, but it will be more expensive. If this turns out to be the case, we will advise all our customers accordingly.

Mapping Accuracy
Sure-Path is indicating that I am driving to the left/right but I am pretty sure this is wrong.

First of all check that you have mapped the course accurately. See Guidelines for Tournament for more information on how to check your course mapping.

If you remap the course, remember to "reselect" the course as the Boat Lane after you have done so as any changes to the survey file are not automatically reflected in the boat lane file.

If all the above is good and you still think you are getting erroneous deviations, then we would respectfully suggest that the system is correct. Remember that every boat is different. Even two boats that are the same year and model will sit in the water differently and will drive differently. The boat should always be balanced. If it is available, set up end-course video and compare the results with Sure-Path. If Sure-Path is consistently telling you that you are left or right on successive passes in both directions, then it is definitely you, since any error in the Sure-Path readings in one direction would give an opposite error in the other direction.

Another consideration to bear in mind is that most drivers use a combination of "distance" viewing and the next guide buoy as their reference points as they drive through the course. The tolerance on the guide buoys is roughly +/- 11cm which is a lot when compared with the tolerance allowed for the boat from the centre line (+/- 20cm). If one guide buoy is say 10cm narrow and the next is 10cm wide of ideal, then although both buoys are "in tolerance", it is extremely difficult to drive a good "straight" line relative to the centre of the boat lane.

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