Here 3 RTK GNSS with base : Drones, UAV, OnyxStar, MikroKopter, ArduCopter, RPAS : AltiGator, drones, radio controlled aircrafts: aerial survey, inspection, video & photography
Arducopter Quickstart Guides and Tips - Arduino based Arducopter UAV, the open source multi-rotor
Here+ RTK GPS — Copter documentation
Connecting external LED's to Arducopter | Visser I/O
Buy ThinkRobotics ArduPilot APM2.8 With M8N GPS Online – ThinkRobotics.com
UBlox GPS + Compass Module — Copter documentation
UBlox GPS + Compass Module — Copter documentation
APM 2.8 ArduPilot Mega Internal compass APM Flight Controller Built-in Compass with 7M GPS for FPV RC Drone Aircraft