Re: dash7 pictures

Jason Brown wrote:
> Good, glad you're thinking about it. There's a few good articles on the 
> net, one written by a university team who tried to do this kind of thing 
> using accelerometers. They eventually gave up and incorporated GPS and 
> then got very good results. Sample rate seems to matter a lot when 
> trying to derive speed info from acceleration, but you've already got a 
> direct measure of speed so you might be able to work something out.

My own experience is that 10Hz is accurate enough to map half a lap
accurately, 100Hz gets you a few laps before it spirals off.  Using GPS
correction would get things perfect with just 10Hz resolution since the GPS
gives the layout and the accelerometers are just giving you the values to put
there.  The downside is that you end up using a fair amount more memory
and cycles to do it.

What I've found with just accelerometers is that the straights get elongated
first, then the corners become more wayward and the plot spirals out.  The
speed input will get the longitudinal plot accurate again but it won't cure
the cornering problem. 




 Try 
> here:
> http://www.csl.cornell.edu/~viran/learning/trackmap/
> http://www.analog.com/Analog_Root/sitePage/mainSectionContent/0,2132,level4%253D%25252D1%2526ContentID%253D8082%2526level1%253D212%2526level2%253D%25252D1%2526level3%253D%25252D1,00.html
> 
>>2) I'm using the largest I2C memory available at present. This will
>>obviously change, and when it does...just buy it from your preferred
>>supplier. Install the chip, upload the config data and off you go.
>>  
>>
> That's reassuring, assuming that the manufacturer keeps backward 
> compatibility.
> 
>>Anyone interested in making an application on a palm or pocketpc or
>>whatever, let me know and I'd be happy to give you the protocol info. A
>>number of cool things could be made; to name two - a temporary storage and a
>>graphical front end displaying real-time data...
>>  
>>
> This is the kind of thing I'm interested in. Temporary storage is just 
> useful, and should be simple. I've thought about a real-time display and 
> just about ruled it out, for the same reason that you have alarms - you 
> can't concentrate on the display when driving. I do however have some 
> other potentially cool things to do in real-time, and that's why I was 
> interested in the real-time serial feed.
> 
>>Export to Excel is a no-brainer.
>>  
>>
> Good ;-)
> 
> Please put me on the seriously interested list, and a potential beta 
> candidate if you can use one in the UK. I do about 1,000 miles / month, 
> regardless of the time of year or weather. I might even throw in a 
> winter track day or two.
> 
> Jason.
> www.strangely.org
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