Converting GPS seconds to readable time&date

flamey has asked for the wisdom of the Perl Monks concerning the following question:

How can I convert GPS time in seconds to something readable, say UTC time? For example I have GPS time in seconds = 915725119. I use http://www.mapshots.com/tools/gps_time.asp and get "1/7/1999 4:05:19 PM" -- the time matches what I see on my device (i can't confirm date). I tried Time::GPS and DateTime::Format::Epoch::MJD as follows:

use Time::GPS qw(gps_instant_to_mjd gps_mjd_to_instant);
use Math::BigRat;

my $x = Math::BigRat->new('915717017');
my $mjd = gps_instant_to_mjd($x);
print "$mjd\n"; # 2021871299/43200

use DateTime::Format::Epoch::MJD;
my $dt = DateTime::Format::Epoch::MJD->parse_datetime( $mjd );
print $dt; # 1987-01-06T00:00:00
[download]

Obviously something there is wrong, but what? What's the best way to do such conversion, anyway? Many thanks in advance.

Comment on Converting GPS seconds to readable time&date Download Code

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Re: Converting GPS seconds to readable time&date by derby (Abbot) on Jan 11, 2009 at 14:46 UTC
gmtime in scalar context should do the trick: `perl -e 'print scalar( gmtime( 915725119 ) ),"\n"'` [download] prints `Thu Jan 7 16:05:19 1999` [download] -derby Update:There's a lot of talk about which CPAN date module to use but for whatever reason, I always fall back on Date::Manip. With that module, you have tons of control over lots of most aspects of time: `perl -MDate::Manip -e 'print UnixDate( ParseDate(scalar(gmtime(9157251 +19))), "%m/%d/%Y %i:%M:%S %p"), "\n"'` [download] (there's probably tons of ways to simplify that). Or if you just need a pretty string, you could always use strftime: `#!/usr/bin/perl use POSIX qw( strftime ); print strftime( "%m/%d/%Y %l:%M:%S %p", gmtime( 915725119 ) ), "\n";` [download] (format strings to strftime tend to be platform dependent)	[reply] [d/l] [select]
Re^2: Converting GPS seconds to readable time&date by flamey (Scribe) on Jan 11, 2009 at 14:56 UTC
thnaks for your help, derby. now i don't understand why they called it GPS time in the serial output :-/ , but that's a different issue.. thanks	[reply]
Re^3: Converting GPS seconds to readable time&date by derby (Abbot) on Jan 11, 2009 at 15:23 UTC
Yikes! Found this at leapsecond.com `GPS, Global Positioning System time, is the atomic time scale implemen +ted by the atomic clocks in the GPS ground control stations and the G +PS satellites themselves. GPS time was zero at 0h 6-Jan-1980 and sinc +e it is not perturbed by leap seconds GPS is now ahead of UTC by 15 s +econds.` [download] I'm not sure if your hardware is compensating for this diff and/or if it's just outputting standard UTC and saying it's GPS. You're better off listening to someone more GPS aware than I am (that is if you're really worried about that 15 second gap). -derby	[reply] [d/l]
Re^4: Converting GPS seconds to readable time&date by Anonymous Monk on Jan 11, 2009 at 16:36 UTC
Re^4: Converting GPS seconds to readable time&date by ikegami (Patriarch) on Jan 11, 2009 at 16:58 UTC
Re^4: Converting GPS seconds to readable time&date by zentara (Archbishop) on Jan 11, 2009 at 15:33 UTC
Re^5: Converting GPS seconds to readable time&date (relativity) by tye (Sage) on Jan 11, 2009 at 22:03 UTC
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Re^4: Converting GPS seconds to readable time&date by n3toy (Hermit) on Jan 11, 2009 at 16:31 UTC
Re^5: Converting GPS seconds to readable time&date by hobbs (Monk) on Jan 11, 2009 at 22:01 UTC
Some notes below your chosen depth have not been shown here
Re^4: Converting GPS seconds to readable time&date by JavaFan (Canon) on Jan 12, 2009 at 19:02 UTC
Re^5: Converting GPS seconds to readable time&date by BrowserUk (Patriarch) on Jan 12, 2009 at 19:19 UTC


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