Dead reckoning with BMW zumo works

Discussion in 'Mapping & Navigation' started by dbrown, Mar 24, 2009.

  1. dbrown

    dbrown Adventurer

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    Well It passes my first test. The dead reckoning feature of my BMW zumo 550 works, well maybe. It appears to work with my '08 R1200GS, but I am going to test it further. According to my dealer, this feature does not work with all BMW motorcycles. If your not sure what dead-reckoning is, I've described the feature below. The test I conducted is also described below.

    Dead Reckoning
    The dead-reckoning feature is enabled by use of a CAN-bus connection through the BMW power cable supplied with the BMW zumo 550. When the zumo looses satellite reception, in tunnels, canyons, streets flanked by tall buildings, and such, it takes speed data gathered through its CAN-bus connection and heading data from its internal compass to produce continued position tracking on its display. Of course, dead reckoning is not as accurate as the position tracking provided when the zumo is receiving good satellite signals, but it allows the GPS to continue plotting your position even with temporary satellite signal loss. A a result, you have a better chance of making the correct turn half way through that "urban canyon" of a city street.

    The Test
    To test the capability on my bike I took a detour into a multi-level parking structure, since there are no nearby tunnels or canyons. I drove around one floor of the structure then dropped down one floor before making an exit. When I have done this in our car with our nuvi 760 or Vista C, they have lost satellite reception and stopped tracking my position. My BMW zumo/R1200GS setup continued to track a position. When I download the track from the zumo to RoadTrip, I found a complete, uninterrupted track of the trip, including the nearly two loops in the parking garage.

    Now I will look for a long tunnel and test it again.
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  2. 9Dave

    9Dave Bazinga!

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    One question on your test - while in the garage, did you go to the satellite page and confirm the GPS was not receiving any satellite data? :lurk
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  3. BlueLghtning

    BlueLghtning Riding is my passion

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    Yeah, I don't think dead reckoning would pick up loops in a parking garage. I thought it was more meant for you are going straight through a tunnel and it keeps track of how far you have traveled, but not necessarily where you have traveled.

    I'm thinking your Zumo still had sat reception if you had 2 perfectly loops of tracks in the garage. Maybe the compass can fill in, but that seems iffy?
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  4. dbrown

    dbrown Adventurer

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    The zumo does not have a "satellite" page like some of the other Garmin models. There is however a satellite signal indication on the upper left corner of the menu page that appears after the unit completes it's start-up sequence. It resembles the signal strength meter on many cell phones. According to the zumo manual "When your zumo has aquired satellite signals, the signal strength bars on the Menu page are green. When it looses satellite signals, the bars turn red or clear." More bars equal better signal, with five bars max.

    While circling the lower level of the parking garage the signal varied from three green bars to one red, with several lost satellite signal dialog screens appearing. At one point I stopped the bike, waited about 5 minutes and observed the signal meter--constant single red bar. I then shut-off the bike and zumo, removed the zumo from its mount, and restarted the zumo. I was immediately presented with a no satellite signal dialog. I then slowly walked about 75 feet or so toward the nearest opening in the parking structure, where the signal was again received and a position fix was aquired. At this point I am standing about 15 feet from the opening. I turned and walked slowly toward the bike and quickly lost the signal. I returned the zumo to its cradle and started the bike and zumo...one red bar. Once I was moving it started tracking my position again.

    I doubt that BMW had Garmin add any extra control circuitry for the dead reckoning feature. More likely, they just had Garmin write a little extra code (software) that would "fool" the zumo when paired with a compatible bike and make it "think" it was getting a weak signal, so it would not go into "No Signal" mode. Meanwhile, the extra code is also directing the zumo to get its speed and/or direction data from other sources on the bike. This could explain why I did not immediately get the no signal indication when I returned the zumo to the bike while in the parking garage.




    Yes and no. When using dead reckoning, if you know your starting point, have a means of determining direction and a means of determining speed, you can track your position, even if your direction or speed changes. From what I have read, the BMW zumo is provided tire rotation data through its CAN-bus connection in the power cable connection to certain BMW bikes. This is the same data that is routed to the speedodometer/odometer on the bike, so it is relatively accurate. Combine this with an accurate, continuasly-updated compass heading and you can accurately track your position on a map.

    Here's the rub...the zumo compass is not an electronic compass, so it must have a satellite signal and be moving to give accurate direction indications, or have direction info supplied from another source. By comparison, my Vista C has an electronic compass and the unit can be placed on a table then turned and the compass will react immediately, even to small changes and will do this without a satellite signal. When I placed my BMW zumo on a table and turn it, there is little change, if any, on the compass indication. Another problem...electronic compasses, in general, have problems dealing with motorcycle lean angles.




    So my question now: Is the bike, cradle, or the combination of the two working like a strong antenna or is dead reckoning actually being employed here? If dead reckoning is actually working, what is generating the compass heading data when the zumo looses its satellite signals? ...the computer on the bike? Or is it fixed on the last known heading? That is why I would like to test it in a tunnel, preferably a long one with a direction change. ...No tunnels around here though.

    In either case, I am very pleased that it will accurately indicate my direction and travel while in a parking garage. I have been in a few with multiple unmarked exits and become disoriented while negotiating the maze looking for a parking space or when leaving, take the wrong exit to find myself on a one-way street in traffic traveling away from my intended destination.
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  5. xlcr

    xlcr Stop being a dick, dick.

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    My guess is that the Zumo is just projecting your last known speed onto an existing route or road until reception is resumed.
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  6. 9Dave

    9Dave Bazinga!

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    Thanks for the info. While dead reckoning is a feature, I'd bet it had just enough signal for a fix. I'd think that dead reckoning would know distance and speed, but wouldn't know your turn directions, so the circles in the garage would be straight lines at best.

    It is an interesting question. I wonder what would happen if while in the garage, you took multiple layers of heavy duty foil and shielded that unit totally. I'd think that would be capable of blocking the signal. Then, try your ride through again.:dunno
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  7. dbrown

    dbrown Adventurer

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    Well, I went out and looked at the power cable. The CAN-bus connector plug has only two wires connected. The third pin on the plug has no connection. I was told by a dealer (not the dealer that sold me the unit) that all three pins were connected, two wires for power and one for speed data. The dealer that sold me the unit, installed the cable, so I never had any reason to look at the connector.

    Still, I have had several Garmin GPS receivers over the years. The zumo, from what I have seen so far, has the most sensitive receiver.
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  8. rockies-GS

    rockies-GS Been here awhile

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    never had trouble with my Zümo....
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  9. dbrown

    dbrown Adventurer

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    I'v never had any trouble with any of the Garmin products I've purchased. I was just stating the BMW power cable that came with my BMW zumo has only two wires, even though I have been told by a BMW dealer in the past, that there are three wires in the cable. So either the dealer was mistaken or the cable has been changed by BMW. But my Zumo is working great.
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  10. 9Dave

    9Dave Bazinga!

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    Yeah - the new chipsets are amazing. And the processor speed doesn't suck, either.
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