Spectra Precision ProFlex 800 Reference Manual - Manual (Page 101)

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Using the Web Server
This chart deserves a few more comments and explanations:
• Accuracy has a linear relationship to baseline length.
However a too long baseline length can result in
differential multipath between antennas and introduction
of vehicle flexing into the heading solution. These two
factors are detrimental to heading accuracy. In addition,
the longer the baseline length, the longer the calibration
sequence. That’s why baseline lengths of three to five
meters are recommended. Baseline lengths less than one
meter are not advised.
• Accuracy figures given above are 1-sigma values, or rms,
which means that 67% of the measurements are at or
below these figures.
• Heading accuracy will be about a factor of 2 better than
pitch or roll accuracy. Pitch and roll accuracies are the
same.
• In each figure, the lower line (blue) represents accuracy
achievable if no multipath errors were present. In a normal
environment, this is not possible. Multipath effects from
typical environments are depicted by the upper line (red).
For a given baseline length, the performance of the
ProFlex 800 should lie somewhere near the upper line.
• A moving vehicle does not experience as many multipath
effects as when it is stationary. This is because multipath
is a correlated error. Correlated errors become more noise-
like under vehicle dynamics and therefore can be filtered
out. Therefore, accuracy results improve toward the lower
line (blue) when the vehicle is moving.
Elevation Offset
Ideally, the two antennas should be installed at the same
elevation. You may however be facing some installation
constraints on your vehicle compelling you to install the
0.1
0.1
0.01
0.001
1
1
10 100 1000
Baseline Length (m)
Heading A
ccur
a
c
y
(°)