(Remember this thread is generally for discussion only. Do not let it stop you from observing..) Re : The clock on a cell phone I have just boxed up all my stuff, as a week of rain is expected here on the West Coast of CA.. Next time I have the stuff out, I will have to compare the phone to the KIWI.. I can assure you already that there is no basis for the assumption that the cell phone will have anything resembling accurate timing.. 1) Absolute time is unimportant for most operations and is therefore not provided for in most applications, even when it could be.. 2) We tend to observe when it is 'cold' and LCD latency is also an issue in timing. Latency, and therefore accuracy, would be temperature sensitive. 3) Even if it is 'accurate', matching it to a video field or frame is non trivial.. 4) Even if you can 'stamp' the time, from an accurate time base, onto a video frame, you still have to verify one way or the other that there are not any dropped frames / duplicated frames (or fields as the case may be). Etc.. Easy to test roughly, generally impossible to test "accurately".. (Dismantle the phone, use an oscilloscope....). I would be very surprised if anyone has done this. Another simple test is to go to your local Astronomy Society meeting, and gather everyone's cell phone together and watch the displays on all of them and see if they all change (apparently) at the same time.. Try it again after a couple hours outside when it is 40F or colder when the phones are cold.. Of course yet another underlying issue with "accurate timing" (a subject you may have noticed that I enjoy) is this.. "Do satellite observations need accurate absolute timing (and to what precision)?" No.. All the 'usual suspects' in this group have told me essentially that I could do a lot more if I was to get away from such high precision, but I am an 'old dog and new tricks' don't come easily. A perfect analogy is would you measure a 4x4 post with a micrometer?? Of course not.. I do because I know the underlying time is accurate.. My whole point is primarily a semantic one about "My timings are accurate to +/- (whatever).." My response is *ALWAYS* the same.. "HOW DO YOU KNOW?? Accurate time to one person isn't necessarily accurate to another.. When it involves a manufacturer of a cell phone or a computer, it creates a problem for us users. +/- 0.5s is fairly easy. +/- 0.1s isn't too involved, but does take a little thought and effort. Going below +/- 0.008s (which is the center point of an NTSC / EIA video field)?? That's a Project.. Derek _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-l
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