Common Abbreviations

ACC

Accelerometer

AHRS

Attitude Heading Reference System

ALT

Altitude

ATC

Attitude Control

AP

ArduPilot

APM

ArduPilot autopilot

ARSPD

AirSpeed

ATT

Attitude

BATT

Battery

CTUN

Control Tuning

DCM

Discrete Cosine Matrix (first generation position/attitude estimator)

EKF

Extended Kalman Filter (a predictive filter subsystem)

EK2/3

EKF2/EKF3 (ArduPilot has two generations of EKF based position/attitude estimators in the firmware)

GCS

Ground Control Station

GPS

Global Positioning System

GYRO

Gyroscope

IMU

Inertial Measurement Unit

INS

Inertial Navigation System

PCS

Position Control System

PM

Power Module

RC

Radio Control

TECS

Total Energy Control System (altitude/speed controller for Plane)

WP

Waypoint