| NAV problem brewing, or common?
- Click HERE for Original Thread
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| DaleB |
I have noticed at times, the Nav screen display will be offset about 20 degrees from true North.
I have only seen this happen when first starting out, not while driving for any length of time. After several seconds or when making a turn it will snap back into position.
It happens so rarely it would be hard to duplicate unless it happened with some kind of regularity. |
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| xcel |
Hi DaleB:
___I am not sure if this describes your find or not and I am grasping at straws but most external GPS receivers can only give you a direction once you have started moving after initial startup if I remember correctly? In other words, until you move, the GPS just assumes you are at a given point but gives you no actual direction because it doesn’t have a reference to true north. With an accuracy of ~ 30’ or so, the birds could probably be locked into a lookup table for a particular time of day or from their own position giving true North but I am not sure that is the easiest way or if it is even done. I can see the bird positions around me in the GPS HW screens so I would assume you could pick up true North from that but I only remember seeing a point and as soon as you moved a few feet, the map would swing around to heading up. By the sounds of it, the Acura based NAVI might be tied into the compass or simply remembers the last direction it was headed before it lost the birds due to shut down or losing contact after being driven into the garage? I would be curious to hear other NAVI owners take on this as it is something I have never thought of myself as well as a feature that X owners may never have known they had! It would be very useful none the less. I will have to run my parents new CF based GPS receiver and PDA to see if it gives a semi true north on initial startup but I don’t remember that it did?
___This is a very interesting question (to me anyway) so thanks for bringing it up.
___Good Luck
___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___Waynegerdes@earthlink.net |
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| DaleB |
I think we are just 'touching' on the phenomena. Or walking around it, not sure. What I see happens is not indicative of memory, because the offset is always the same (true N being offset about 20-30 deg toward NW).
It could be a default position when the NAV is not receptive to compass orientation. Like it is asleep for a few seconds, but it does display a full map. |
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| xcel |
Hi DaleB:
___I know I was a bit un-descriptive in my post above but that is because I am not sure exactly how a hand held functions on first boot and fix as far as its actual true direction is concerned. I can always see a map with or without a fix but am not sure as to what direction is shown as up no matter where true North actually is. Again, this is only on first fix after being turned on. I guess what I will do is turn on my parents GPS receiver while motionless and once it receives a fix, I will turn in a circle (on a dime of course) to see if it spins the map or not? Afterwards, I will walk a few feet, let it pick up my heading and then shut it off again. I will perform the same to see if the hand held remembers its last fixed direction or it starts from scratch on each boot and fix as well as if it will give a true North direction by Bird position or not?
___A bit OT but I have the ability to turn off “Map Heading Up” through Mapopolis so I will have to experiment with that as far as direction on first fix is concerned as well?
___Why don’t you pull your X into the garage or up the drive backwards and see what happens when you turn on the X and it receives first fix? If your heading is 180 degrees out, that should tell you something about how it either remembers its last heading or how it initializes with a direction whether true North is actually 22.5 or so degrees off or not? I also seem to remember that true North and compass North are a bit off from one another as well but not 22.5 degrees off?
___After reading the above, it will probably sound like gibberish to most but I am very curious now as to how a Hand Held works just before and after initial fix as well as your X. Unfortunately, my mouse based GPS receiver is permanently mounted in the X and it’s in Champaign, IL. right now.
___Good Luck
___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
___Waynegerdes@earthlink.net |
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| DaleB |
Typically it locks to true north immediately, no matter where I am. But on occassion will go into this 'slump' mode for several seconds when first turned on. That's about the only way I can describe it.
It could be a slow to initiate compass, and the receiving electronics just defaults to that mode if there is no direction input. At least it appears to be acting that way when it happens. |
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| jimfr |
| Not familiar with exactly how the Alpine system works, but the Nav system I worked on (as a coder) would display a best guess direction when the unit was first switched on. Once you start moving, the nav system corrects the guess with accurate information. On systems with road lock (which locks the GPS direction onto a current street), this can sometmes take a minute or two and will often require that the car be moving at a minimum speed to do so. |
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| DaleB |
| Well, this is a random problem. I guess it is a problem because it seems no one else has seen it exhibited in their X. |
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