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| Coordinates | Time Series | SCOUT | ||||||||||||
| Scripps Coordinate Update Tool (SCOUT) Documentation |
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The Scripps Coordinate Update Tool (SCOUT) can be used to compute mean coordinates of a specific site, by submitting a RINEX file of a particular day. The file may be uncompressed, or in .Z, .gz or .bz compressed format. Both standard observation (o) and hatanaka-compressed (d) files are accepted.
The location of the RINEX file should be given in the form of an ftp-URL (e.g., ftp://yourmachine.com/pub/rinex/123/site1230.98o.Z). The best place to store the file is in the pub directory of your machine, which can then be accessed by anonymous ftp. Make sure outside users are allowed to retrieve the file by setting the appropriate file permissions, if required. If outside users are not allowed to access your system, you can upload your rinex file to ftp://geopub.ucsd.edu through non-anonymous ftp. Login is "scout" and password is "coordgen". Logging in as the scout user will place you in the "pub/scout" directory; use the "put" command to ftp the RINEX files to this directory on geopub.ucsd.edu. Note: you will not be able to see your files after you've uploaded them, but they do exist. The rinex files that are available in this directory are shown under the "None" pulldown in under the "Select a RINEX file..." section. To update this list after you've sent your file, hold down the Shift key and press Reload (or Refresh) on your browser. Selecting one of those files will override any entries made in the URL-box. Note: SCOUT uses the GAMIT processing software package, which supports these model types. Do not attempt to submit RINEX data from different models while selecting dummy equipment types. The reference stations which are used in the analysis are by default the three nearest sites for which data are available on that specific day. If the RINEX header does not contain approximate xyz coordinates, these will be estimated by SCOUT, and used to determine the nearest sites. Most of the time, this will give the best results. However, in some cases it may be useful to use different reference stations. This can be achieved by providing up to four valid station ID's (four characters) in the appropriate box. Station maps may assist you in determining other nearby sites. RINEX filenames should follow the standard naming convention. This is of the form AAAADDDS.YYo, where AAAA is the unique four code station ID, DDD is the day of the year, S is the session number (0 for the whole day) and YY is the two digit year. The actual data should comply with the official RINEX definition, or no analysis can be performed. A useful tool to check the format of your data is teqc, which is available at UNAVCO. After supplying this information, the RINEX file will be retrieved through anonymous ftp. The four character station ID is then compared to the Scripps Orbit and Permanent Array Center (SOPAC) site database. If the site is recognized, the site parameters (e.g., antenna type, receiver, firmware, etc.) will be obtained using this database. However, if the station code is not recognized, you will be asked to provide the following information: receiver type, antenna type, receiver firmware, and antenna height. The firmware codes are as follows: ASH = Ashtech, LEI = Leica, ROG = (Turbo)Rogue, and TRM = Trimble. The height from the geodetic monument reference point (MRP) to the antenna reference point (ARP, often the bottom of the pre-amplifier) must be in meters. The analysis will be performed by means of a simultaneous network adjustment with the nearest reference sites. These sites will be chosen from the list of stations which are currently processed by SOPAC, in order to achieve the highest possible accuracy. It is critical, therefore, that the mandatory XYZ coordinates in the RINEX header are valid, and as accurate as possible. If the coordinates are not given in the header, absolute positioning will be used to estimate the intitial values. After the nearest sites have been determined, the analysis job is queued and automatically processed in the order in which it was received. If you entered different reference stations, the nearest sites are overruled and your reference sites are of course used in the analysis. When the analysis is completed, a report will be send to the e-mail address which you have provided. The report will include mean cartesian and geodetic coordinates for your site (valid for the epoch of the day processed), standard deviations, a map which shows the location of the two sites and the approximate baseline-length between the two stations. The cartesian coordinates are referenced with respect to the International Terrestrial Reference Frame 2005 (ITRF2005). The geodetic coordinates are also referenced with respect to ITRF2005, but projected onto the ellipsoid of the World Geodetic System 1984 (WGS84). In some cases the software will not be able to generate an acceptable solution. This will mainly be due to poor data quality, corrupted data (i.e., not RINEX compatible), or when providing incorrect site information. If a solution can not be formed, you will be informed and the analysis group can examine the solution manually at your request (time permitting). Fatal analysis problems also occur when the time tags of your RINEX file do not coincide with the time tags in the RINEX file of the reference station. In this case, no double differences can be formed. Your data should be sampled at least every 120 seconds and should coincide with a whole or half a minute (e.g., observations taken at 13h:21m:00s and 13h:21m:30s, but NOT at 13h:20m:58s and 13h:21m:28s). The naming of your rinex file should also reflect the actual data. That is, if the naming of your rinex file is site2610.98o.Z, there should actually be data available in this file for day 261 1998 and the "TIME OF FIRST OBS" tag should be properly set.
SCOUT uses a minimum time span requirement of 1 hour. Please note that files less than 3 hours may cause a high formal error to occur, represented by a high standard deviation of the output values; while the solution is not necessarily bad, the chance of it being poor is greater than usual. This is due to a limited number of satellites in view during this short time. If reference sites are far away, e.g., > 500 km, satellite position ambiguities are difficult to resolve. To confirm your solution, provide longer session data, or confirm your initial solution by performing additional short session solutions.
We would like to hear from you! Please send any questions, concerns or suggestions about this tool to the webmaster.
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