Product specifications

10
C HAPTER 2: I NTRODUCTION
O VERVIEW
This chapter provides a brief introduction to the Crescent Vector module and some of
its high-level features. The remaining chapters provide more detailed information on
the workings of the product and the integration requirements.
For your convenience, both the GPS and SBAS operation of the Crescent Vector
module features automatic operational algorithms. When powered for the first time,
the Crescent Vector system will perform a ‘cold start’, which involves acquiring the
available GPS satellites in view and the SBAS differential service.
If SBAS is 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 an eight data bit, no parity,
and one stop bit configuration (8-N-1). Additionally, since the Crescent Vector is a
low-level module, it will need to receive corrections at a 3.3 V CMOS signal level.
This chapter describes the various modes of operation and features of your Crescent
Vector module.
GPS
The GPS engine is always operating, regardless of the DGPS mode of operation. The
following sections describe the general operation of the Crescent Vector module.
S ATELLITE T RACKING
The Crescent Vector module automatically searches for GPS satellites,
acquires the signal, and manages the associated navigation information
required for 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. SNR information is
provided by the Crescent Vector through the use of NMEA 0183 data
messages available via its multiple serial ports.
H EADING A CCURACY
The Crescent Vector has a heading accuracy of 0.5 degrees 95% with an
antenna separation of 0.5 meters. This heading accuracy can be increased
with an increased antenna separation, but, with the trade off of slower
acquisition and reacquisition times. For more information, please refer to the
white paper on the Crescent Vector OEM.