From Jeff Tue Feb 23 00:00:00 1993 From: Jeff (Jeff) Date: 23 Feb 1993 00:00:00 Subject: [IGSMAIL-204] Re Message-ID: From: Jeff Freymueller Subject: Re: No 201: Proposal to standardize receiver and antenna names in RINEX ----------------------------------------------------------------- The name standardization proposal put forth by Ulf Lindqwister, Werner Gurtner and Miranda Chin (in IGS Mail Message 201) is a good one, but I have a few additional suggestions. This topic also brings a few other ideas and questions to mind, which I will deal with after my comments about the proposal. For those who want to skim through this message, a quick summary is - Comments on proposed naming conventions - What are the monument inscriptions? - How were heights to Rogue and TurboRogue antennas measured? In short, as a user of the IGS data (rather than a participant in IGS), I think that we need to do a better job of site documentation than has been done so far. COMMENTS ON THE PROPOSED RECEIVER AND ANTENNA NAMING CONVENTIONS > > The list below proposes a standardization of the receiver names and > antenna names... > > Trimble > ------- > > Receiver Type Description > > TRIMBLE 4000S 4000SL and 4000SX (single frequency) > TRIMBLE 4000SD 4000SLD (dual freq. L2 squaring) > TRIMBLE 4000ST 4000SST (dual freq. L1 c/a, L2 squaring or p-code) > TRIMBLE 4000SE 4000SSE (dual freq. p-code on L1 and L2) The RINEX format allows 20 characters for receiver name. I see no reason to truncate Trimble's three letter typename to two letters. Fourteen characters has no obvious advantages over fifteen! More importantly, this list leaves out the Trimble 4000SDT, a receiver which was used for some field campaigns in 1989 and early 1990. It was an intermediate unit between the SLD and the SST. It was the last Trimble receiver which could not sample on the integer GPS second. > > Antenna Type Description > > GEODETIC L1 To use with Single frequency geodetic receiver > GEODETIC L1/L2 " Dual " > KINEMATIC L1 antenna without a ground plane > KINEMATIC L1/L2 " There have been at least three types of Trimble "Geodetic" antennas, called the SXD, SLD and SST antennas. As far as I know, all three use the same microstrip, but the dimensions of the ground planes and the preamp units are different. Another antenna type is the built-in antenna that sat on top of the receiver unit in some cases. Even though all but the SST are now historical, our naming convention should not ignore them. The mean phase centers for all these antenna types (and probably the variation with azimuth and elevation) are different, due to the dimensions of the package being different if nothing else. The advantage of distinguishing between an L1 and L1/L2 antenna is not clear. As far as I know, the L1 phase centers are identical for both types. If that is true, then very little useful information is conveyed by making the distinction. The only case I can think of where it might make some difference is that if a dual frequency receiver was using a single frequency antenna, knowing so would explain the lack of L2 data! > > Ashtech > ------ > Receiver Type Description > > MD-XII Dual freq. L1 c/a and L2 squaring > P-XII Dual freq. p-code on both L1 and L2 Don't forget the Ashtech L-XII receiver, which is similar to the MD-XII. I don't remember what the differences are, except that the L-XII was the earlier model.. > > > Antenna Type Description > > GEODETIC L1/L2 Dual freq. with a ground plane > MARINE/RANGE Single freq. with a smaller ground plane > A-C L1 Single freq. without a ground plane for aircraft use > A-C L1/L2 Dual freq. without a ground plane for aircraft use > There have also been at least two Ashtech "Geodetic" antennas. Again, the microstrips are the same but the physical dimensions differ. MARKER NAMES It was decided early on in the IGS campaign that the "MARKER NAME" record of the RINEX files should contain the four character site ID rather than the actual marker name. In my opinion, this is not very useful since the four character ID is also given in the file name. Furthermore, receivers have been known to move to different monuments from time to time. I maintain that in 5 years everyone will be hard pressed to remember what "KOK2" was, or what happened at USUDA, or what distinguished the three sites all named "CANB" (two moves in 1992, before the start of the IGS Campaign). Marker inscriptions, on the other hand, do not change with time and thus are a more useful permanent identification. I suggest that there should be more discussion on this topic (perhaps by email between interested parties). Even if it is necessary for some software to read the four character site ID from the RINEX file, there is nothing to prevent the actual marker inscription from being given in a "COMMENT" line in the RINEX file. On this topic, I have read through all the IGS mail messages except for a few that I missed (and was unable to find), and I have yet to see a complete listing of the marker inscriptions for all the IGS sites. Examples of sites I have not seen inscriptions for are: CANB, FAIR, MATE, MCMU, METS, NYAL, GOLD, PAMA, SANT, STJO, TAIW, USUD, YARG, DARW, and MASP. While certainly some of these 15 are due to ignorance on my part, it is clear that it is time (past time!) for a complete list to be compiled and distributed through the IGS Mail. I would like to say that the information given about the Pie Town and North Liberty sites is exactly the way it ought to be done in the future. The monument inscription, site ID, antenna type and antenna height were all given at the time the receiver started tracking. I think it is important for all future IGS sites to follow this example! ANTENNA HEIGHTS JPL has always distributed antenna heights measured to the TOP of the choke rings. While not in accord with the RINEX standard, which would specify the base of the antenna unit (where the screw mount is located), at least it is a well-defined point. It is worth noting that the RINEX point, at least on the TurboRogue antenna, is NOT the base of the rings themselves - but rather the base of the ring unit (which is 3.4 cm below the base of the actual rings. The 10.16 cm ring height includes this. It is not clear how some of the other heights have been measured. If a height is given as being to the base of the choke rings, does this mean the base of the rings, or the base of entire unit? TurboRogue antenna: ____ / \ ---------------- <- TOP of choke rings | | | | ---------------- <- base of the actual rings - if a slant height | | was measured it would probably be to here. ------ <- RINEX point Also, most of the JPL sites have antenna heights given as 16.30 cm to the TOP of the choke rings. This height has been reported for sites with both Rogue and TurboRogue antennas. Since the choke rings have different heights, it is not clear how the same mounting system would give exactly the same height to the top of the choke rings. Jeff Freymueller (jeff at pangea.stanford.edu) Stanford University