Vector Sensor Reference Manual 45
3. Overview
This chapter provides a brief introduction to the Vector Sensor system and some its high-level
features. The remaining chapters provide more detailed information on the workings of the
product and the integration requirements.
As mentioned in the previous chapter, if you are new to GPS and SBAS, we recommend that you
consult Appendix C for further information on these services and technology.
For your convenience, both the GPS and SBAS operation of the Vector Sensor features automatic
operational algorithms. However, you must program the Vector Sensor for which differential
service to use. The Vector Sensor does not automatically choose one service over the other. By
default, the Vector Sensor operates with SBAS corrections.
When powered, the Vector Sensor system will performs a ‘cold start’, which involves acquiring
the available GPS satellites in view and the SBAS and beacon differential services, if available.
Acquisition of a GPS heading is also automatic, however, you are able to force a new heading
search if needed.
If SBAS or beacon corrections are not available in your area, an external source of RTCM SC-104
differential corrections may be used. If you choose to use an external source of correction data,
you will need to ensure that the external source supports RS-232 and an eight data bit, no parity,
and one stop bit configuration (8-N-1) and also configure the Vector Sensor for external
correction operation.
3.1 GPS
The following sections describe the general operation of the GPS technology within the Vector
Sensor.
3.1.1 Satellite Tracking
The internal GPS receivers automatically search for GPS satellites, acquire the signal, and manage
the associated navigation information required positioning and tracking. This is a hands-free mode
of operation. Satellite acquisition quality is described as a signal to noise ratio (SNR). A higher
SNR is indicative of better quality signal reception. The primary GPS receiver supplies SNR
information via $GPGSV NMEA 0183 data messages that may be output through either Port A or
B.
3.1.2 Positioning Accuracy
The Vector Sensor provides sub-meter 95% accurate positions under ideal conditions horizontally
(minimum error). Since the Vector Sensor will be used in the real world, multipath signals and
GPS signal blockages may reduce the level of system performance. To aid in challenging
environments, the CDA-RTK antennas feature multipath rejecting technology to reduce the
effects of multipath.
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