Now let's get down to some nitty gritty.  How does one get from the data to the rate?  Look at the SOPAC Data Archive page.  Choosing the first option: Find Data (SOPAC database source) leads to a dialog window that allows you choose a range of days and a range of sites to download data for those days. 

Hark! A voice from the future: Scripps has instituted some changes since I wrote this and while I've tried to update, I can't promise all these links work as advertised. For a broader perspective, look at this.

Entering "cotd" in the site field and 200 to 210 as the range of days for the year 2000 for instance will (with a little luck) produce a table titled "Data Availability (obs) - 200, 2000 to 210, 2000" with links to the data of each of the 11 days showing availability at 99%.  Clicking one should give you the option of saving the file containing the data to your local disk.

Now what?  Well...for better or worse, there's a webdoc that explains, to some degree, how to read these data: Hatanaka and RINEX Format Information.  
The intructions for this have changed, so a lot of this stuff is out of date.

In the second section (GENERAL FORMAT DESCRIPTION) we read that there are 4 files in ASCII format:
                   1. Observation Data File
                   2. Navigation Message File
                   3. Meteorological Data File
                   4. GLONASS Navigation Message File
and that each consists of header section and a data section.

The header section gives information types of observations in the data. Each Observation file and each Meteorological Data file basically contain the data from one site and one session.

3. DEFINITION OF THE OBSERVABLES

GPS observables include three fundamental quantities that need to be defined: Time, Phase, and Range.

TIME:

The time of the measurement is the receiver time of the received signals.  It is identical for the phase and range measurements and is identical for all satellites observed at that epoch. It is expressed in GPS time (not Universal Time).

PSEUDO-RANGE:

The pseudo-range (PR) is the distance from the receiver antenna to the satellite antenna including receiver and satellite clock offsets (and other biases, such as atmospheric delays):

PR  =  distance + c * (receiver clock offset - satellite clock offset + other biases)

so that the pseudo-range reflects the actual behavior of the receiver and satellite clocks. The pseudo-range is stored in units of meters.

See also clarifications for pseudoranges in mixed GPS/GLONASS files in chapter 8.1.

PHASE:

The phase is the carrier-phase measured in whole cycles at both L1 and L2. The half-cycles measured by sqaring-type receivers must be converted to whole cycles and flagged by the wavelength factor in the header section.

The phase changes in the same sense as the range (negative doppler). The phase observations between epochs must be connected by including the integer number of cycles. The phase observations will not contain any systematic drifts from intentional offsets of the reference oscillators.

The observables are not corrected for external effects like atmospheric refraction, satellite clock offsets, etc.

If the receiver or the converter software adjusts the measurements using the real-time-derived receiver clock offsets dT(r), the consistency of the 3 quantities phase / pseudo-range / epoch must be maintained, i.e. the receiver clock correction should be applied to all 3 observables:

                  Time(corr)  = Time(r)  -  dT(r)
                  PR(corr)    =  PR(r)   -  dT(r)*c
                  phase(corr) = phase(r) -  dT(r)*freq

DOPPLER:

The sign of the doppler shift as additional observable is defined as usual: Positive for approaching satellites.
 

Ok, well...this is a work in progress.  My difficulty is currently in how to interpret the raw data such as shown below: