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Motion Detection on a Car Camera Explained.

Most car cameras (pretty much all infact) come with "motion detection" and this can often cause the owners some confusion as to how it works when it appears that their camera is not functioning correctly.  Here's an explanation of what this feature is, what it does and how it is best used  to help you get the most from your dash cam, whichever model you have chosen.

Primarily, "motion detection" is a function of the camera, but it can also be seen as a sub-function of what is known as parking mode on some cams, whereby parking mode may (and almost always does) utilise the function of "motion detection" whilst the car is stationary.  This is a very important consideration, as we can immediately see that the detection of movement is tied in very closely with being parked!

With the above in mind, it is first worth solidifying that motion detection is strictly to be used in a parked car.  This applies without exception, irrespective of the make or model of the dashcam.  The reason for this is that it will only record if something is moving within its field of view.  When nothing moves, the camera goes into "watch" mode and stops recording.  This is no good if you are sat at traffic lights waiting to move off and someone hits you from behind as the camera will not be recording anything.  (Bear in mind that being hit from behind with only a front view camera recording will still give you evidence of fault).

When power is supplied to the camera, but the car is parked (power is normally provided by a hardwire to the car battery) the camera can remain "ON" as it were.  This gives rise to the opportunity of recording whilst the car owner is not present.  However, in-turn, long duration parking becomes an issue because the memory card may quickly fill up with videos containing nothing but a view of the cars opposite (envisage a car park with the camera pointing forward - and what the camera is looking at). What's worse, is that loop recording will also start to overwrite old footage within a few hours (memory card size dependent) which may cause the loss of a clip containing a bump.

To get around these issues, the camera is placed in "motion detection" mode.  On some more expensive sophisticated models, this switchover is accomplished automatically with firmware within the camera deciding when the car is parked via a combination of a change in the power supply and/or remaining still for a while (detected via lens movement and/or shock sensor inactivity). 

Motion Detection on a Car Camera.

On normal cameras or earlier models, the owner must park the car and then go into the menu to select the motion detect option.  Either way, once selected video will only be created whilst there is something happening in front of the lens of the camera in terms of objects (cars or people (or birds!)).

Lets take a quick look at the sequence of events as they may occur in a real-life situation.

a) Car is parked up and ignition switched off - power supplied by car battery so camera still has electricity supply.
b) Camera placed in motion detection mode.  (either automatically or manually).
c) Cam is now "waiting" for movement in its field of view.
d) Movement occurs.
e) Recording starts - and continues until motion has stopped (for longer than x seconds - x normally around 15).
f) Recording stops
g) Go to c) until owner of vehicle moves car, or switches to normal recording mode.

At point e) above, you may ask yourself how fast the recording kicks in.  This is a commonly asked question and there are two answers.

Simpler model units will incur a delay of a second or so after movement is seen before the footage starts to be captured - thus the approach of a vandal may be seen, but may be missing the first couple of seconds.  More complex systems incorporated into those car cameras with a "true" parking mode feature will actually store footage from a number of seconds BEFORE movement aswell as footage after activity ceases therefore increasing the chances of preserving details such as facial images or the number plate of an offending vehicle.

Motion Detection In summary

"motion detection" is a memory saving feature which only records footage where motion is taking place.
You should NEVER drive your car with it enabled - as this will confuse the camera as you stop and start at lights etc.
Some cameras have built-in methods of activating it automatically when the car stops.
Power is drained from a source at a similar rate whilst in this mode - even though it may not be recording, the camera requires power to maintain surveillance.

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