[Ssc-dev] quick note on Carrie's work

[Hans-Christoph Steiner]

On 08/23/2013 03:09 PM, Nathan of Guardian wrote:
> Adding Harlo to this thread, and cc'ing the list, as this is an
> important general topic.
> 
> On 08/23/2013 03:06 PM, David Oliver wrote:
>> Here's one thing I want to know to aid in this process:  As I understand
>> it, having a single accelerometer reading is useless for determining
>> anything about movement, it is the comparative readings that are important.
>>  Using, say, 3 readings, you could assert something about motion.  But,
>> InformaCam does not know "I should collect an accelerometer reading just
>> before the picture is taken, then one during, then one after - since it
>> does not know when media is created.  Yet, you can't possibly gather
>> accelerometer (and/or compass) in real time all the time and then wait to
>> use it.......so what does InformaCam actually do?
> The question is then, how/when are we logging accelerometer data, and
> what can or should we infer from it?

The easiest thing to derive from accelerometer data is the directly of
gravity, i.e. the orientation of the device.  Gravity is a constant
acceleration (i.e. force), and accelerometers measure acceleration (and not
position or speed). That's why phones have them, then the phone knows which
way is down.

As for getting more information from them, you need to have many readings per
second, like 100 or 1000 even, in order to get useful results.

Sounds to me that reading the accelerometer directly would be only useful for
InformaCam in very special cases, and cases where battery life is not so
important.  Most of the time, InformaCam should just log the orientation from
the Android API and not bother reading the accelerometer.

.hc

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