GPS files are now accessible via the World Wide Web!
The files are collected on an hourly basis and stored as (.zip) files. The files are available 5 minutes after the hour they are collected.
To download the files, first, read the following caveats, then, simply click on the DOWNLOAD button where you will be shown a directory structure
based on the file type. Click on the desired ZIP file to download the file to your local hard disk.
Each RINEX file is named using a ssssdddh.rin.zip format. ssss represents the
four character station name (CSAL), ddd is the Julian Date, h is the hour
long UTC time block, and rin is the file type. For example, a RINEX file
from this site containing data for 3:00 pm to 4:00 pm (central standard time) on
February 17, 2003 would be named CSAL048v.rin.zip
All other files are named using a yymmddhh.zip format. yy represents
the year, mm is the month, dd is the day, and hh is the hour long UTC time
block.
There are a few of things you will want to know before downloading.
1. Important notes about browser behavior during downloading. READ THIS BEFORE PROCEEDING!
2. Data are collected in SYNCHRONIZED mode, so you may need the SYNC2RAW file.
3. How to compute the file names you need, or, how to convert your local time to UTC time. IMPORTANT!
1.
We have switch from using .EXE files to .ZIP files because of the following reasons:
Problem Description: One major problem we have noticed is that the .EXE file may be treated as a self-installing executable program by the Netscape browser during the download. The system starts a new browser session that attempts to download the same EXE file. This happens over and over until the machine locks up.
A different problem occurs with Microsoft Internet Explorer. Apparently IE3.x doesn't properly close sessions with the FTP server we use, causing error messages on multiple downloads.
2.
Problem Description: If you are using an older version of GPS correction software, your software may not properly read the base data because it is collected in SYNCHRONIZE mode. This mode allows newer rover units to collect carrier phase signals and differentially correct for sub-meter accuracy.
Solution: Download the SYNC2RAW.EXE conversion utility and use this program to convert the SSF files you obtain here into the older RAW format. Don't try this unless you cannot process the SSF files. You will find the SYNC2RAW file in the "special" directory on the FTP server. Just follow the links to download and look for the "special" directory.
3.
Problem Description: Base data files are named by the Trimble Community Base Station (TCBS) software (ie, the software that collects the data) according to the time they were collected in UTC (universal time coordinate) time. UTC time coincides with Greenwich Mean Time (GMT), which is in turn the time to which all time zones refer. Note that GMT coincides with the Prime Meridian.
Solution: Read the instructions describing UTC time conversion process.
