In the CWEX11 S directory at EOL is a file of Splus code, latlonalt.q, for computing averages of the GPS values of latitude, longitude and altitude.
I ran it on 6 days of data from Jul 9 11:15 to Jul 15 16:00 (arbitrary period), and it returned the following:
stn  | 
Lat(deg)  | 
Lat stddev(deg)  | 
Lon(deg)  | 
Lon stddev(deg)  | 
Alt(m)  | 
Alt stdev(m)  | 
|---|---|---|---|---|---|---|
1  | 
42.06605  | 
1.101896e-05  | 
-93.28521  | 
9.501855e-06  | 
338.998  | 
1.798216  | 
2  | 
42.06977  | 
1.317406e-05  | 
-93.28515  | 
1.091214e-05  | 
340.4294  | 
1.796624  | 
3  | 
42.07344  | 
1.417124e-05  | 
-93.28522  | 
1.358779e-05  | 
340.0666  | 
1.977678  | 
4  | 
42.07679  | 
1.39572e-05  | 
-93.28523  | 
1.211881e-05  | 
341.577  | 
2.024058  | 
Note that the altitude estimates have a std deviation of around 2 meters
Here's a kml file: cwex_ncar.kml with the above positions.