[Gta04-owner] Advance OpenStreetMap surveying with GTA04? / accelerometer patch

[Mayeul Kauffmann]

Hi,
Great, that was fast! Looking forward to see the results of the test
and, hopefully, get something to test integration!

> I still have to read all these links

Then yet another, better than the other 5: from link [3], click on
"resources" tab (goes to
http://www.pololu.com/catalog/product/1250/resources ).
Second link in "resources" gives the math and geometry too. There is
link on mbed Library for the LSM303DLH

Thanks,
Mayeul

Le lundi 19 mars 2012 à 22:29 +0100, Christoph Mair a écrit :
> Hi,
> 
> On Mon, Mar 19, 2012 at 1:44 PM,  <mayeul.kauffmann at free.fr> wrote:
> > Hi,
> > Thanks Christoph. Comments below:
> >> There exists a simple hack that reads the raw
> >> acceleration values from the chip and delivers them to userspace using
> >> a sysfs file
> >
> > I've read [0] but could not find it description of this hack. Any pointer and sample strings?
> 
> I attached a patch to get some values from the BMA180 accelerometer.
> It should apply to the 3.2-gta04 tree. I have not tested it lately, so
> it may just fail. When my flat battery is recharged I can test it too.
> 
> > The LSM303DLH combines both 3D compass and accelerometer, so is the HMC5883L usefull for this application?
> 
> We planned to use the LSM303DLH but we could not buy it in time.
> Therefore we had to find a replacement. The BMA180 and the HMC5883l
> have better specs than the LSM303 so the replacement should bring us a
> slight improvement in accuracy.
> 
> > So one idea is to put some tilt logic in the code here:
> > http://gitorious.org/vala-compass/vala-compass/trees/master/src
> > Or write a piece of code that takes the raw data and output tilt-corrected magnetic heading.
> > I found out some math and code (for Arduino) that could be re-used. Most interesting are [3] to [5]:
> >
> >
> > [1] Has nice geometric discussion and code, but cannot correct for tilt over 40 degrees. Saysthere are other (more complex) algorithms for tilt > 40°.
> > [2] Give some pointers to scientific articles, including I believe for 360 degrees correction.
> > Note that typical use is keeping the device vertical, so code in [1] is not OK
> > [3] Discusses the LSM303DLH chip included in the GTA04, and gives 2 links for code computing the tilt-corrected heading:
> > [4] Arduino code for LSM303DLH
> > [5] In "Ressources" tab: "library for the ARM mbed development board that interfaces with the LSM303DLH 3D compass and accelerometer carrier and provides the tilt-compensated magnetic heading"
> >
> > Isn't [5] the closest to what would be needed? Could it serve as a basis?
> 
> This sound very promising. I still have to read all these links
> (hopefully tomorrow) but the last one is probably what you need.
> 
> Christoph
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