POS MV V4 User Guide
Theory of Operation
Copyright © Applanix Corporation, 2009
B-29
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rΔ
=
surveyed antenna baseline vector - the vector
that joins the two GNSS antennas; because
the IMU and the GNSS antennas are mounted
rigidly on the vessel, this vector remains fixed
Note: The example shown in
Figure 74 is greatly simplified. It shows only the
relative yaw angles made by the baseline vectors. In practice, the
transformation of one baseline vector to another may possibly involve
rotations in all three axis - roll, pitch and yaw.
Baseline Measurement
Geographic Antenna Baseline Vector
To compute a highly accurate value for Ф
ANT
based on carrier phase
differential GNSS, GAMS must first resolve the phase ambiguities in the
differential carrier phase observables.
The GNSS receivers in POS MV use the L1 GNSS signal, which has a carrier
frequency of 1575.42 MHz and a wavelength of 19 cm. You can consider the
range between each GNSS satellite and a GNSS antenna as an integer
number of L1 wavelengths plus a fraction of a wavelength.
Each receiver can measure the fraction of a wavelength from each tracked
satellite but cannot determine the integer number of wavelengths between the
transmitting satellite and the antenna.
By using satellite pseudo-range, the receiver can reduce the uncertainty in
knowing the integer number of wavelengths to less than 100. The remaining
unknown integer number of wavelengths is the carrier phase ambiguity.
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