On 2008-03-11, chowalit.lab Chowalit Lab Linux <[EMAIL PROTECTED]> wrote:
> So It's wrong on my GPS (GPSmap60). The problem with the GPSMAP 60 is that it is the wrong type of GPS receiver for an application which needs highly stable time. There are two types of GPS receivers: mapping and timing. The key difference between these two type of receivers is that the timing receivers provide a Pulse Per Second (PPS) output which is typically aligned to within 1 microsecond (0.000001 sec) of UTC time. Higher quality timing receivers may be capable of closer (e.g. nanosecond) alignment. Both types of receivers are able to emit NMEA sentences via a serial or USB interface. These NMEA sentences are emitted when the receiver is not busy doing other things such as processing satellite data, updating the display, etc., and can occur at _any_ _time_ during second they are valid for. Time sources utilizing only NMEA sentences are not suitable for a Stratum 1 time server. It is up to you to decide if the GPSMAP 60 is good enough for your requirements. The USD249.99 GPSMAP 60 is a mapping receiver. The USD74.50 GPS18 LVC is a timing receiver. GPSMAP 60 https://buy.garmin.com/shop/shop.do?pID=224&tab=gpsmap60#specsTab GPS 18 OEM https://buy.garmin.com/shop/shop.do?cID=158&pID=223 > Oh... So If I still use this GPS I should add offset with fudge > option. You may correct (i.e. fudge) the approximate offset but not the massive jitter inherent in the NMEA sentence(s). You also should enable only one of the NMEA sentences to reduce the receiver's workload. >Can I get other source from this GPS? No. The GPSMAP 60 is not a timing receiver and does not provide a PPS signal. -- Steve Kostecke <[EMAIL PROTECTED]> NTP Public Services Project - http://support.ntp.org/ _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
