WinFrog User’s Guide - Appendix C – GPS/MX 9400
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vehicle) to the device (antenna) location. Offsets Fore and Starboard are entered as
positive values, offsets measured Port and Aft are entered as negative values. Rule
of thumb suggests the CRP “Z” reference should be at the water line.
DGPS Mode:
Select the desired mode of DGPS operation
There are four different DGPS modes: Auto, On, Off and Generate.
Auto:
WinFrog will automatically use differential corrections in its position
calculations, when available. If no corrections are available, WinFrog will
compute a single point (aka autonomous) position solution.
On:
WinFrog will always attempt to use differential corrections. If no corrections
are available, no position will be computed.
Off:
WinFrog will not use differential corrections in its position computations,
even if they are available. Instead it will always compute a single point GPS
solution.
Generate:
WinFrog will generate differential corrections based on a fixed
reference position. This option is used for Base Stations only.
Phase Smoothing:
Phase smoothing utilizes the GPS receiver’s observations of the GPS satellite’s
carrier signals. Because the GPS L1 frequency has a wavelength of only 19 cm.,
measurements made using this signal will provide higher accuracy than
measurements made on the C/A code message modulated onto the L1 signal. Note,
however, that since the carrier phase position is derived from the C/A code position,
it does not offer an improvement in precision.
If the Phase Smoothing feature is enabled, WinFrog will use the C/A Code derived
(DGPS corrected) position to derive the number of L1 wavelengths to each of the
observed satellites. Over the length of time entered into the
Filter Length
field
(value in seconds), WinFrog will switch the GPS calculated position from the C/A
code position to the derived Carrier Phase position.
WinFrog will continue to use the carrier phase data to provide positioning until the
Cycle Slip Tolerance
is exceeded. A Cycle Slip is the loss of lock on a satellite’s
signal. This loss of lock forces WinFrog to re-establish the number of wavelengths
from the antenna to the satellite. If the number of cycle slips exceeds the Cycle Slip
Tolerance, WinFrog will resort back to the C/A code position and re-calculate the
number of wavelengths to all received satellites.
