Missing GPS data... sometimes

[butako]

Sometimes recorded video footage is missing GPS data, and sometimes it's present. I can understand why GPS would be missing at the beginning of a journey, but it's also the case several minutes into the trip. It is not consistent, sometimes GPS is OK. What are the reasons for no GPS please?

 

[jokiin]

GPS dropouts are typically due to poor signal, if your can has athermic windscreen, heated windscreen etc this will cause it, check your owners manual for the car, if you have an affected windscreen they will often mention it, there may also be mention or a section of the window which is untreated that is transparent to the signal

if all that checks out you could have a faulty camera, if that's the case just talk to the seller about getting it replaced

 

[M8TJT]

Please clarify your exact problem. Do you mean:
A. Sometimes the unit does not get a GPS lock (Co-ords on recording) for an extended period after start up?
or
B. After obtaining a GPS lock, your unit subsequently looses lock later during the same journey?

 

[butako]

Hi M8JTJ, the symptoms are (A).
Reviewing camera footage I am seeing that sometimes it lacks GPS after the car has been driving for several minutes.

 

[M8TJT]

Your symptoms are quite common and depends a lot on how clear a view of the sky the receiving aerial has.

Simplistically (very), GPS works by triangulation on a minimum of three points: two moving satellites and the receiver. But the system knows where the sats are in relation to one another.
If the receiver is also moving, this makes the triangulation so much more difficult as all three points are now moving.

The longer a 'sat location' device has been switched off, the longer it will take to achieve a lock. This is also true if the device is moved a large distance without it being switched on and tracking.

The way to overcome this 'problem' and get a faster sat lock, it to wait until you have one before moving off or put up with not having GPS data for the first part of the trip (as you are getting).

 

[M8TJT]

The signal from the sats is never poor (but it is jolly weak). Its the receiver's location, the receiver's sensitivity or something between the receiver and the sats that's not obvious like an athermic windscreen as noted by jokiin above, that causes it to be poor.
Rain can affect reception, but it needs to be seriously heavy before it does. Overhanging trees, especially wen wet. Limited view of the sky because of surrounding buildings (urban canyon) etc, etc.

The GPS will take varying times to lock onto the sats, and if you drive off before it has locked on, then it takes considerably longer (can be miles) to get a really solid robust (multiple sats) lock (as observed by the OP) and may become unlocked again if any of the above apply before it has picked up enough sats to make it more robust.