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1. Overview
1-1 Introduction
Alpha is a high performance RTK receiver with multiple interfaces, including UART, USB, and Bluetooth.
It offers centimeter-level positioning accuracy suitable for survey, mapping, GIS data collection, and
outdoors robotic precision guidance.
By default, Alpha is shipped as RTK rover to accept RTCM3.x message or SkyTraq carrier phase raw
measurement data from a RTK base, and provide centimeter-level accurate position result relative to
the RTK base in standard NMEA message format. Alpha can also be configured as a RTK base to
provide RTCM3.x message or SkyTraq carrier phase raw measurement data output.
Alpha has three major interfaces for different applications. The USB interface is mainly used for
configuration, monitoring, and supplying power. With Bluetooth V2.1+EDR module built-in, Alpha can
be used as external Bluetooth RTK receiver for Android Mobile Device to provide higher accuracy
positioning than internal GPS. The 3.3V LV-TTL UART interface allows simple connection to controllers
for precision guidance applications, replacing normal meter-level accuracy GPS receiver.
Alpha can easily connect and use with Pixhawk / ArduPilot using the supplied connector cable,
enabling UAV to navigate with centimeter-level position accuracy. Unique to Alpha is camera shutter
triggered RTK position stamp function, which is much more accurate than alternative time stamp
based linear interpolation approach to re-generate camera triggered position for aerial survey
application.
1-2 RTK Operation Guidelines
To provide centimeter-level RTK accuracy, Alpha requires much better operating condition than
conventional meter-level accuracy GPS receiver:
Baseline distance between base and rover should be under 10Km.
Open sky environment without interference and signal blockage
Received signal level should be no less than 40dB/Hz.
12 or more satellites over 15 degree elevation angle
Good satellite geometry with satellites spread over four quadrants of the sky.
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