Sensors that can quantify factors related to crop, animal, and woodland production and environmental management are the foundations of digital management.  When those sensors are interconnected and communicate in real time, that concept is Internet of Things, or IoT.  Sensors can be mounted on satellites, airplanes, unmanned aerial vehicles or drones, ground-driven implements, or in fixed or semi-fixed locations on plants or animals or in the soil.  Common measurements include geographic coordinates, electromagnetic reflectance within the visible, near infrared, thermal, and other spectrums, temperature, pressure, speed, resistance, vibration, and humidity.