From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-we0-f171.google.com (mail-we0-f171.google.com [74.125.82.171]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id 711EC200A2E for ; Fri, 16 Mar 2012 19:07:00 -0700 (PDT) Received: by werm1 with SMTP id m1so7857259wer.16 for ; Fri, 16 Mar 2012 19:06:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type:content-transfer-encoding; bh=JzqiJSn40uNFq1Vg7qlOFkMpbJQRpyE/oLsk+JXkxNk=; b=a/LD7B4bUN5iuNGkjbWU9FrpkofoiLxMy7YCzKjAcbzqSXl/oakxbT91omcoGTl4Fb Dl7fx/cob1y0qiiXvx1Rolj0elu5e6VfxlncaVTZXqfoPaxwW/J42myiBzR6iD+8hS34 EH+zUDa0WhYVEFirOgWaCQkMfGK1Jzhlh9W9A1npauZwZGIJhsBk5PEyK6ArbvFyN/tp jtZXmx2B1oqsePyMguAFrL3HW+SRqnuLbBvxQXOznichox8pgXscmGAWADD9W2jnO0UV dNBX5I5ceE4uPSxnE48hNhiZ5OF3gNkfSSCGl4k68JWDExqDQH1BPdG/sbmqAfkRpgV+ T3kA== MIME-Version: 1.0 Received: by 10.216.202.99 with SMTP id c77mr3479106weo.5.1331950018456; Fri, 16 Mar 2012 19:06:58 -0700 (PDT) Received: by 10.223.151.8 with HTTP; Fri, 16 Mar 2012 19:06:58 -0700 (PDT) In-Reply-To: <20111025095801.C9A9D800037@ip-64-139-1-69.sjc.megapath.net> References: <20111025095801.C9A9D800037@ip-64-139-1-69.sjc.megapath.net> Date: Fri, 16 Mar 2012 19:06:58 -0700 Message-ID: From: Dave Taht To: thumbgps-devel@lists.bufferbloat.net Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Subject: [Thumbgps-devel] Fwd: Long term SiRF data X-BeenThere: thumbgps-devel@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 17 Mar 2012 02:07:00 -0000 I can't remember if I had shared this already. ---------- Forwarded message ---------- From: Hal Murray Date: Tue, Oct 25, 2011 at 2:58 AM Subject: Long term SiRF data To: Eric Raymond Cc: Hal Murray , Dave Taht , Jim Getty , Gary Miller I've been collecting data from 2 SiRF units. =A0I'm up to about 12 days now= . Quick summary: both suck. Both are located inside my house, poor conditions. The first is a Holux GR-213. =A0It's setup to only send GPRMC sentences. That's what I would use with ntpd. Here is the startup: =A0http://www.megapathdsl.net/~hmurray/bb/gps/Holux-1.png The green marks are "good" sentences. =A0The Y offset is the difference bet= ween the actual arrival time and the time stamp in the sentence. =A0The blue mar= ks are the fraction part of the time stamp in the sentence. =A0The red marks a= re invalid sentences. At about -2.94 (hours) the reported time jumped by 1 second. =A0My guess is that it learned about the latest leap second or something like that. At about -2.82 hours, the fractional part of the report switched to 0. =A0I have no idea what caused that. =A0It doesn't really matter much. =A0It wasn= 't useful anyway. Here is the big picture: =A0http://www.megapathdsl.net/~hmurray/bb/gps/Holux-2.png There is a mode shift every 1-3 days. =A0What's the right term? For reference, here is an old graph with the mode shift every 8-12 hours. =A0http://www.megapathdsl.net/~hmurray/bb/gps/SiRF-GPRMC-4800.png This is the previous 2 pictures glued together: =A0http://www.megapathdsl.net/~hmurray/bb/gps/Holux-3.png Here is one day: =A0http://www.megapathdsl.net/~hmurray/bb/gps/Holux-4.png ------------- The second unit is a Global Sat BU-353. =A0It ignored my attempts to change= the configuration, so I let it run in the default setup. =A0Normally it sends GPGGA, GPGSA, and GPRMC. =A0Every 5 seconds it includes 3 GPGSV sentences before the GPRMC. =A0I think that fits in 1 second at 4800 baud, but the GP= RMC gets pushed over to the next second. Here is the graph for the GPGGA sentences: =A0http://www.megapathdsl.net/~hmurray/bb/gps/BU-353-gpgga.png The long term cycle time is 8-10 days. Here is the graph for the GPRMC sentences: =A0http://www.megapathdsl.net/~hmurray/bb/gps/BU-353-gprmc.png The top band of green is the data that gets pushed over to the next second. The blue and purple are the number of satellites. =A0(They are scaled up by 100.) =A0I don't see any pattern. This unit doesn't always return 000 for the fraction part of the time stamp= . Sometimes it's 998 or 999 with the previous second. =A0http://www.megapathdsl.net/~hmurray/bb/gps/BU-353-gpgga-off.png -- These are my opinions, not necessarily my employer's. =A0I hate spam. --=20 Dave T=E4ht SKYPE: davetaht US Tel: 1-239-829-5608 http://www.bufferbloat.net