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imapbox
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 Posted: Fri Aug 13, 2004 7:55 am Post subject: how long does ASN hold the speed/direction ? |
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I asked to tomtom.nl support. they don't know. I have tried it in a tunnel and found out (although this was v4.2.0) that it stops updating after a short while, the tunnel is 6 km or so and it stopped after say, a minute...
others who have the same observations ?
also they declined to tell what technique they used. as far as I know, it's a two axis accelerometer, with some form of dead reckoning. anyone who has more info ?
seriously, it's hard to get more and interesting information, like what hardware approximately is used. it seems a nice device to load other software as well. (linux of course). it would be nice to have a proof of concept X window system running, connected via USB or something. just for fun.
push in the original SD card and it's a tomtom go again.. but as said, it's hard to do, if you don't even have the kernel sources available (GPL, they should at least have it available for us, but there hasn't been an anser to that yet, will take some time) |
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alix776
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Joined: 03/05/2003 14:45:49
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Location: leyland lancs ENGLAND
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| Posted: Fri Aug 13, 2004 5:30 pm Post subject: |
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it wont carry on all the way through the dartford tunnel but pick the gps signal us straight any when you emerge at the other side
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Oh the joys of being a courier.
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imapbox
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| Posted: Mon Aug 16, 2004 9:04 pm Post subject: |
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| alix776 wrote: | | it wont carry on all the way through the dartford tunnel but pick the gps signal us straight any when you emerge at the other side |
how long is this tunnel ? the schiphol tunnel is ok, without a problem. will see how long that is. I think ASN will fail after a minute or so.
weird things as well. black/white screen, no ASN flashing and... the screen gets updated where I drive ..
happened a few times when I was in belgium this weekend. the TTGO helped me 100% to stay on track btw. |
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lbendlin
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| Posted: Mon Aug 16, 2004 9:25 pm Post subject: Re: how long does ASN hold the speed/direction ? |
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| imapbox wrote: | | . it seems a nice device to load other software as well. (linux of course). |
The GO is actually running Linux.
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Lutz
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imapbox
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| Posted: Mon Aug 16, 2004 9:50 pm Post subject: Re: how long does ASN hold the speed/direction ? |
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| lbendlin wrote: | | imapbox wrote: | | . it seems a nice device to load other software as well. (linux of course). |
The GO is actually running Linux. |
I know. it was the only reason to get it. both the palm and pocketversions die within minutes on my hands. the TTGO keeps running here..
anyways:
I was referring to stuff like make the TTGO a time reference for the systems here for instance. or have X running on it. or make it a simple PDA. stuff like that. fun stuff. |
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tazcab
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Joined: Jul 27, 2004
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Location: Essex, UK
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| Posted: Fri Aug 20, 2004 4:07 pm Post subject: |
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| :D my one keep carry on all the way through the dartford tunnel till i emerge at the other side vershion 4.21 with ANS just incase i get lost in tunnel |
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MrT
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Location: Surrounded by A1, M1 & M25
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| Posted: Sat Aug 21, 2004 6:48 am Post subject: |
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| I thought is was just a simple mathematical interpolation of the previous data. It happens on the TomTom on a PDA and there are no inertial or gyroscopic sensing devices in that. |
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imapbox
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| Posted: Sat Aug 21, 2004 9:36 am Post subject: |
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| MrT wrote: | | I thought is was just a simple mathematical interpolation of the previous data. It happens on the TomTom on a PDA and there are no inertial or gyroscopic sensing devices in that. |
http://www.gpspassion.com/forumsen/topic.asp?TOPIC_ID=7908
states :
"While this is not mentioned in the specs, I have been able to confirm today with Mr. Pauwels, TomTom's CTO, that TomTom Go uses an accelerometer that combines the features of a gyro and speedo connection - for genuine tracking with a GPS, for up to 5 minutes! This is a first for any consumer navigation system as far as I know"
if dead reckoning is used, you are not able to sense any hchanges in direction as it's only mathematic. if the above test is 100% right, the tomtom has two acellerometers that sense acceleratin/decelleration on the x- and y-axis. combined with the current speed and the map, you can still update your position and mix this position with the GPS data so that you keep the present position accuracy within limits, even when you pick up the GPS data again.
so, if this information is correct, it's different than the simple idea of mathematic interpolation of previous data.
I btw noticed that sometimes, ASN kicks in when you have some stuff above you like fly overs etc; I recently turned the TTGO normal instead of upside down, hanging on the sucktion feet and found, hat now the antenna is facing up again, works much better. (of course this is normal but I just wanted to say that the difference is pretty huge) |
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MrT
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| Posted: Sat Aug 21, 2004 10:14 am Post subject: |
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| Interesting, I am wondering what speedo connection it is talking about? |
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imapbox
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| Posted: Sun Aug 22, 2004 12:50 pm Post subject: |
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| MrT wrote: | | Interesting, I am wondering what speedo connection it is talking about? |
none as far as I know. it's not necessary either given the fact that changes in GPS position will not only show direction but changes integrted in time, will give us speed. so the speed is known until the moment the GPS signal is lost. but then, you can have a two axis accelerometer that detects chanes in speed so you still can draw a vector to know where you go and the size of the vector.... is the speed. however, accelerometers of this kind only will work for a short time, especially if the speed is constant.
if the TTG would have been equipped with a gyro & accelerometers attached to it, it would change the story, the price, reliability and startup-time..... |
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lbendlin
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| Posted: Mon Aug 23, 2004 12:05 am Post subject: |
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Folks, this is not rocket science here. It's a simple combination of two solid state gyros (like you find them in model aircraft). There is no connection to the speedo, and none is required.
One Gyro senses the forward acceleration (what you could call X axis) and the other one lateral acceleration (turns, so to speak.). No speed measurement is done, it's all purely done with acceleration calculations.
So it doesn't matter if the acceleration is zero (the speed is constant) - fine, let's use the same speed. But any acceleration value obviously influences the speed, in both planes.
Since the gyros have a finite sensitivity they need a certain amount of acceleration to be triggered - that's what eventually leads to the disconnect with reality after a while. But hopefully by then the GPS signal has kicked in again.
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imapbox
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| Posted: Mon Aug 23, 2004 5:33 am Post subject: ASN gyro or Accelerometer only ? |
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| lbendlin wrote: | Folks, this is not rocket science here. It's a simple combination of two solid state gyros (like you find them in model aircraft). There is no connection to the speedo, and none is required.
One Gyro senses the forward acceleration (what you could call X axis) and the other one lateral acceleration (turns, so to speak.). No speed measurement is done, it's all purely done with acceleration calculations.
So it doesn't matter if the acceleration is zero (the speed is constant) - fine, let's use the same speed. But any acceleration value obviously influences the speed, in both planes.
Since the gyros have a finite sensitivity they need a certain amount of acceleration to be triggered - that's what eventually leads to the disconnect with reality after a while. But hopefully by then the GPS signal has kicked in again. |
I happen to know how the laser- and normal gyros work. for the solid state ones, I know the vibrating models. do you happen to have some URLs that describe what kind(s) might have been used ? the ones I see so far are too big to fit with the electronics in int and would make the TTGO too pricey.. |
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delboy0754
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| Posted: Mon Aug 23, 2004 5:38 am Post subject: |
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| lbendlin wrote: |
Since the gyros have a finite sensitivity they need a certain amount of acceleration to be triggered - . |
They are sensative. To prove this, you only need to walk with the TT Go. I have a walking disability, but it still registers me at the blistering speed of 1mph |
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lbendlin
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lbendlin
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| Posted: Mon Aug 23, 2004 2:03 pm Post subject: |
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| delboy0754 wrote: |
They are sensative. To prove this, you only need to walk with the TT Go. I have a walking disability, but it still registers me at the blistering speed of 1mph |
Are you sure that's not the GPS receiver registering the speed? Remember, this thread is about the ASN.
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