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| author | Eric S. Raymond <esr@thyrsus.com> | 2012-05-24 19:11:54 -0400 |
|---|---|---|
| committer | Eric S. Raymond <esr@thyrsus.com> | 2012-05-24 19:11:54 -0400 |
| commit | e4feb0441f9299441efe1b000d65381fabc6402f (patch) | |
| tree | db5caa9091add4e6dab95721c0d0161644d10586 | |
| parent | 354c438607bfabcc4877c60310c5144b429d941d (diff) | |
| download | gpsd-e4feb0441f9299441efe1b000d65381fabc6402f.tar.gz | |
Clarifications on time service.
| -rw-r--r-- | www/hardware-tail.html | 32 |
1 files changed, 16 insertions, 16 deletions
diff --git a/www/hardware-tail.html b/www/hardware-tail.html index 94fe0df7..3e354a22 100644 --- a/www/hardware-tail.html +++ b/www/hardware-tail.html @@ -2,23 +2,23 @@ <h2 id="timing">PPS and GPSD:</h2> -<p>Many GPS receivers offer a 1PPS (one pulse per second) output that - GPSD is capable of passing along to <code>ntpd</code> for use as an - extremely accurate clock source. The "Claimed Accuracy" are taken - from manufacturers' data sheets, and have not been independently - verified.</p> +<p>Some GPS receivers offer a 1PPS (one pulse per second) output that +GPSD is capable of passing along to <code>ntpd</code> for use as an +extremely accurate clock source. The "Claimed Accuracy" figures are taken +from manufacturers' data sheets, and have not been independently +verified.</p> - <p>Where specified, NTP time offsets have been measured by - comparison with the NTP time service and reported by - <code>gpsd</code>.</p> +<p>Where specified, NTP time offsets have been measured by +comparison with the NTP time service and reported by +<code>gpsd</code>.</p> - <p>Note that either a direct RS-232 connection or the "Magic Macx -mod" (1PPS on the GPS chip connected to DCD on the serial-to-USB -adaptor) is required for optimal PPS timing. Typical gpsd/PPS users -report ntp clock stability on the order of 1uSm for RS232, 1ms for -USB).gpsd can extract from GPSes that are native USB but not -PPS-capable time information from the serial data accurate to about -250mS.</p> +<p>Note that either a direct RS-232 connection or the "Magic Macx mod" +(1PPS on the GPS chip connected to DCD on the serial-to-USB adaptor) +is required for PPS. Typical gpsd/PPS users report ntp clock stability +on the order of 1μs (microsecond) for RS232, 1ms (millisecond) for +USB. From GPSes that are native USB but not PPS-capable, GPSD can +extract time information from the serial data accurate to about +250ms.</p> <div> </div> @@ -133,7 +133,7 @@ PPS-capable time information from the serial data accurate to about </tr> <tr> <td>Rockwell Jupiter</td> -<td align="center">1usec</td> +<td align="center">1μsec</td> <td align="center">-</td> <td align="center">-</td> </tr> |