Is GPS chip control affected by 'sensor aiding'?
<p>I had come to the conclusion that the two parameters passed to requestLocationUpdates(minTime, minDistance) don't make any difference to conserving battery power on my phone (Gingerbread), as the satellite icon stays on all the time and the GPS status never goes to TEMPORARILY_UNAVAILABLE as reported by some people in the past.</p>

<p>Therefore I farmed out the control of the GPS to a service which had a timing Runnable in order to control the GPS myself. The service is a simple state machine with three states, IDLE, SEEKING and FIXED_AND_SLEEPING. When the machine is SEEKING the GPS is enabled, when it gets a fix of sufficient accuracy, it calls removeUpdates, to turn the GPS off and starts a Runnable which times out after a period set by a parameter in the service Binder interface and switches updates back on again and moves to state SEEKING.</p>

<p>I thought I'd pretty well nailed this in terms of controlling wheteher the GPS was on or off, as the icon came on and off according to the arguments passed to the machine and log lines showed the state changes as I'd expected.</p>

<p>However, my phone has a feature described as:</p>

<p><strong>Use sensor aiding: "Set to use sensors to enhance 
pedestrian positioning when the GPS signal is obstructed. 
There may be variations between the sensor estimates and 
your actual location"</strong></p>

<p>If I turn this on then I see log lines whizzing past saying something like </p>

<p><strong>[HYPOS] NOMOVE Time 234940, PowerMode 0, GPSWeakSignal 181, GPSFixTime 0, Car 1, DOE 3</strong></p>

<p>and the GPS icon sometimes turns off when I hadn't told it to. Well of course it's not moving as the phone's on my desk with the USB cable plugged in for capturing the logcat.</p>

<p><strong>I'm wondering if this is the purpose of that minDistance argument to requestLocationUpdates?</strong></p>

<p>It never could have determined whether the GPS stayed on or not by using the GPS alone, as the GPS needs to be on to know how far the phone has moved.</p>

<p><strong>Is it the case that if sensor aiding is turned on, then the accelerometers can integrate over a time, get an approximate idea of distance travelled and decide the phone's not moved further than the minDistance and tell the GPS chip to turn itself off?</strong> </p>

<p>I tried to see what would make it come back on again, but as soon as I unplugged the USB to take the phone for a walk, the icon immediately lit up again.</p>

<p>In the absence of Android developers giving a definitive statement on this, any opinions or experiences with this will be gratefully received</p>
