Ground GNSS Ionosphere Sounding - GNSS Remote Sensing: Theory, Methods and Applications - page 70

Fig. 4.3 The RMSs of the differences between receiver DCB values estimated by M_DCB and
those released by CODE, JPL, and IGS-combined

can estimate the DCB for multiple stations or one station. In the following sub-
sections, the test results using a multi-station network and a single station are
presented, respectively, which are evaluated using the IGS solutions, such as those
by CODE, JPL, and IGS-combined.

4.2.1.1 Test Results of Multi-stations

The DCB values of the satellites and receivers are estimated from January 1-31,
2010 using the M_DCB software. Here DCB estimate values released by CODE are
regarded as reference values to validate the M_DCB result. CODE uses 15 orders
of spherical harmonic functions to describe the global total electron content of the
earth's ionosphere every 2 h. Both global GPS and GLONASS observations are
used during DCB estimation ( http://www.aiub.unibe.ch/ ) . DCB values estimated by
M_DCB and those released by CODE are compared in Table 4.1 . Receiver DCB
biases are slightly larger than those for satellites, but most of them are less than
0.4 ns except PRN1 whose DCB bias reaches 0.746 ns. The RMS of all differences
is lower than 0.3 ns. Since the number of valid observations (when the elevation
angle is more than 20 ı ) for PRN 1 is approximately a quarter of the other satellites
each day from January 1-31, the larger bias in PRN 1 is probably caused by fewer
observations.