![]() The typical drone that your cousin might have, or one that recorded the really cool aerial video footage from your favorite TV show probably looks a little bit like an extra-large insect with four horizontal propellers. There are many subcategories, and they range from insect-size to passenger jet-size, but as long as an aircraft is powered and unmanned, it’s a drone by definition.Īny aircraft that has a propulsion system (e.g., battery, fuel… just no gliders) and does not carry humans is considered a drone, though the FAA often uses the terminology “UAS” which means an unmanned aerial system, and refers to the flying object, the pilot on the ground, and the means of communication between the two.Īs the definition of a drone is quite broad, it’s probably no surprise to hear that drones come in many different shapes and sizes. Some extremely small drones, often used for surveillance, utilize ornithopters, which are flapping-wing mechanisms making the drones appear to be insects to anyone not looking closely! Drone DefinitionĪ cut-and-dry drone definition is any powered aircraft with no humans onboard. Many drones possess an array of sensors to relay information to the person controlling the drone, including collision sensors to keep them from crashing. A diagnosis of neutropenic nadir after chemotherapy typically lasts 7–10 days.Most of the drones used in the commercial world are powered by lithium-polymer batteries and utilize a quadcopter mechanism (4 horizontal propellers) to stay in flight. ![]() In oncology, the term nadir is used to represent the lowest level of a blood cell count while a patient is undergoing chemotherapy. Generally in medicine, nadir is used to indicate the progression to the lowest point of a clinical symptom (e.g. A satellite ground track represents its orbit projected to nadir on to Earth's surface. A nadir image is a satellite image or aerial photo of the Earth taken vertically. Nadir also refers to the downward-facing viewing geometry of an orbiting satellite, such as is employed during remote sensing of the atmosphere, as well as when an astronaut faces the Earth while performing a spacewalk. The Sun is said to be at the nadir at a location when it is at the zenith at the location's antipode and is 90° below the horizon. This can be used to describe the position of the Sun, but it is only technically accurate for one latitude at a time and only possible at the low latitudes. The term can also be used to represent the lowest point that a celestial object reaches along its apparent daily path around a given point of observation (i.e. Specifically, in astronomy, geophysics and related sciences (e.g., meteorology), the nadir at a given point is the local vertical direction pointing in the direction of the force of gravity at that location. Since the concept of being below is itself somewhat vague, scientists define the nadir in more rigorous terms. The direction opposite of the nadir is the zenith.ĭefinitions This diagram depicts a satellite observing backscattered sunlight in the nadir viewing geometry. The nadir ( / ˈ n eɪ d ɪər, - d ər/, also UK: / ˈ n æ d ɪər/ Arabic: نظير, romanized: ( listen ⓘ), lit.'counterpart') is the direction pointing directly below a particular location that is, it is one of two vertical directions at a specified location, orthogonal to a horizontal flat surface. Note that the zenith is opposite the nadir. Diagram showing the relationship between the zenith, the nadir, and different types of horizon. Look up nadir in Wiktionary, the free dictionary.
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