Delivered-To: igsmail@igscb.jpl.nasa.gov Message-ID: <3EC4283A.5050106@jpl.nasa.gov> Date: Thu, 15 May 2003 16:52:26 -0700 From: "Angelyn W. Moore" User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.0.1) Gecko/20021003 To: igsmail@igscb.JPL.NASA.GOV Subject: [IGSMAIL-4379]: data smoothing in IGS RINEX Sender: owner-igsmail Precedence: bulk ****************************************************************************** IGS Electronic Mail 15 May 16:52:28 PDT 2003 Message Number 4379 ****************************************************************************** Author: Angelyn Moore Dear IGS Colleagues, You probably noticed quite a few messages from station operators regarding data smoothing earlier this spring. This message is intended to explain further and make a general announcement about it. The IGS CB was made aware that Ashtech RINEX data, when the available Ashtech smoothing corrections are applied, may contain incorrect P1 and P2 values. One detectable manifestation of this is that the L1 multipath figure has a drift with respect to time, within a given satellite arc. We attempted to detect which IGS sites may be applying this smoothing by looking at the L1 multipath. In most cases the answer was clearly 'yes' or 'no' but some sites' data was inconclusive. Due to this uncertainty as well as an incomplete understanding of what the impact of the smoothing corrections was, we began by contacting the operators of Ashtech sites identified as probably smoothing. We asked that they check whether it was true and if possible, set smoothing to off. As usual, many site operators were quickly responsive, and confirmed that smoothing had been set 'on' but would afterward be set to 'off'. It's now clear that this action did have a noticeable effect and the drift of L1 with respect to time was removed. Some operators of Ashtech sites might not have received the original message, due to the L1 slope tests being initially inconclusive. Therefore, this message now serves as a general request to operators, and a reminder to those who could not quickly respond to earlier emails. Procedures for turning off smoothing appear below. Please note that the -general- question of whether data should or may be smoothed is separate from this issue, which is specific to Ashtech receivers. If you have any opinions or evidence on the general question of smoothing, please forward them to me or igscb@igscb.jpl.nasa.gov for consideration in upcoming revised station operating guidelines. Otherwise, if you operate an Ashtech receiver, please consider turning off smoothing in the RINEX creation step as follows: - For teqc: not using the +smooth option. teqc defaults to not applying the smoothing, but if you received teqc from Ashtech, it may have +smooth turned on. - For ASRINEXO: set "L2 FIT / PR SMOOTH FLAG" to 0 - For Micro-Z's with firmware > CN00: avoid "Data Mode 7" with the smoothing option. In this case the unsmoothed data is not saved for possible use at the RINEX conversion step. You're invited to let me know of any of the following (if you have not already): - If you cannot make this change at your station - If you use another RINEX translator and cannot identify how smoothing would be switched off. Finally, please feel free to let me know if you have any other questions! Best regards, Angie ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Angelyn W. Moore, Ph.D. Deputy Director, IGS Central Bureau JPL/Caltech Angelyn.W.Moore@jpl.nasa.gov 4800 Oak Grove Dr. MS 238-540 voice: +1 818 354 5434 Pasadena CA 91109 USA http://igscb.jpl.nasa.gov fax: +1 818 393 6686