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by thanksgiving 2279 days ago
I have been playing with my (spare) Android phone and its GPS to record my location and speed when driving. My guess is when using an app on Android, there are too many variables (from the actual GPS hardware, device ROM settings, app settings, etc.) which are not very easily accessible and likely optimized for different goals.

In my use case (as in the article) only care about GPS readouts when the car is in motion so I don't really care about energy efficiency (within reason, the cigarette lighter thing should be able to safely power the device).

The GPS module manual says it takes about forty seconds for the GPS module to position.

https://images-na.ssl-images-amazon.com/images/I/81+jY5X2YrL...

> Once the GPS module is powered on, there is data output > It usually takes about 40 seconds to be successfully positioned. > After the positioning is successful, the correct time, latitude and longitude position data will be available.

But the article says:

> GPS is usually acquired within 15-30 seconds of starting (much faster than the cheap electronic speedometers I tested first).

Maybe this does not include the time it takes for the raspberry pi to boot? Maybe the raspberry pi takes an additional thirty seconds to boot and the GPS unit powers on almost simultaneously with the raspberry pi but we don't blame the GPS module for any delay until the raspberry pi boots, logs in, and the Navit application starts?

Or maybe the GPS positions way before forty seconds and the manual is written that way to not be overly optimistic (could never get decent GPS signal when walking in areas with tall skyscrapers on my Android phone a few years back).

This is also exciting because it is modular. When GPS III[1] (hopefully) becomes operational by the end of the decade (The tenth and final GPS Block III launch is projected in Q2 2023 so it should be fully operational/adopted by 2030), you could simply use a new module (in theory at least).

[1] https://en.wikipedia.org/wiki/GPS_Block_III

1 comments

You are right; I didn’t factor in RPi boot time to that figure. I’d guess maybe 60-90 seconds total? By the time I’ve turned the ignition, backed out of the driveway, and put it in drive I have a GPS lock.
You can make a Pi boot much faster than that. The main thing to disable is wait for network available. Other embedded boards I've used eg Rock960 are ssh-able within about 20 seconds or less.

Edit - much much faster (4 secs), actually: http://himeshp.blogspot.com/2018/08/fast-boot-with-raspberry...

Not sure if this is unusual, but it takes me ~10 seconds to turn on my car and pull out of the driveway. What are you doing for 60-90 seconds?
I’ve been watching ChrisFix and Scotty Kilmer in Youtube and while they don’t agree on much both say you should wait a few seconds after starting the car before driving away.

Something about engine oil and lubrications. Probably doesn’t harm anything in the short term but if you have time, probably not a bad idea.

I live on a busy city street.
Ah, gotcha. Yeah, that makes sense. :)
Looking out for other cars?