C-Nav Hardware Reference Guide
83
Chapter 6 ........................................................................ Glossary
Troubleshooting
The following information is provided for the use and operation of C-Nav DGNSS Systems. It is
recommended that you read through this chapter before calling C-Nav Support. Refer to p. 2 for
C-Nav 24/7 support contact information. You can also visit
www.cnavgnss.com/faq
for a list of
Technical Support and Product-related frequently asked questions.
Up-to-date information on all C-Nav Products can be found at
www.cnavgnss.com/products
Increasing GNSS Accuracy
C-Nav GNSS receivers will give the most accurate position with a C-Nav corrections
subscription. These corrections are Real Time Gypsy (RTG) which are global in coverage. The
system can also decode SBAS type system corrections as a fall back measure. By control of the
various GNSS parameter settings, optimal GNSS satellite configurations are maintained,
preventing less accurate positions from being computed. However, these parameters can
prevent reliable positions from being output as well. If your GNSS application can tolerate
occasional outages, then more accuracy is possible by changing the various GNSS receiver
parameters from their default values.
The receiver must have sufficient satellites and signal from either SBAS (WAAS/ EGNOS) or C-
Nav Subscription Service sources to achieve advertised accuracies. The geometry also plays
an important role in navigation, meaning that the GNSS signals received must have good
dispersion. This dispersion reduces errors by providing wide angles for trilateration algorithms to
more accurately compute position.
GNSS receiver parameters that affect accuracy are:
•
Elevation Mask
- Raising this mask prevents the receiver from using some low
elevation satellites, often a source of inaccurate positions.
•
Dilution of Precision (DOP) Mask
- Decreasing the DOP mask prevents GNSS
satellites of poor geometry from contributing to inaccurate positions.
•
GNSS Mode
- Three-dimensional positions are more accurate than two-dimensional
positions, so changing the receiver to Manual 3D prevents 2D positions from being
computed.
Local conditions may have an impact on accuracy. Interference, such as harmonics from co-
located transmitting antennas, and multipath, induced by reflective surfaces in the proximity of
the antenna, can be harmful to the quality of the measurements used within navigation. A
relatively uncontrolled source of position inaccuracy is multipath noise, caused by reflections of
the GNSS signals from nearby structures, buildings and flat surfaces. For best accuracy, mount
the GNSS antenna so it has a clear view of the sky. Accuracy is best when operating away from
structures. The same problem of masking can also occur in the reception of C-Nav Signals from
the geo-stationary communication satellites. The user must take care to ensure that a clear and
unobstructed view of the sky is maintained for C-Nav GNSS Antennae, and that no RF
interference sources are present.
Summary of Contents for 1000
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