ArduSimple simpleRTK3B Development Boards are affordable and low-power dual/triple band GPS/GNSS RTK boards that allow reaching millimeter-level accuracy in minutes. The main component of simpleRTK3B is Septentrio Mosaic. These development boards are used as an external GNSS for Pixhawk and Ardupilot. The simpleRTK3B development boards are powered by a GPS USB port, XBEE USB port, Pixhawk connector, and Arduino rail sources. These boards are designed to track any movement with a latency below 10ms and go up to 50Hz attitude tracking without the need for RTK position. The simpleRTK3B boards offer advanced configurations such as antenna offset settings, upload antenna calibration files, and RTCM 1021/1023 support for local coordinate systems. The RTK3B development boards support different operating modes such as standalone, base-rover configuration, base-multiple rovers configuration, and RTK heading. These development boards operate at a 4.5V to 5.5V voltage range and -40°C to 85°C operating temperature range. The RTK3B development tools reduce convergence time, increase ambiguity fixing rates, and increase overall cm-level position availability.