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Digital remote sensing uses advanced electronics to gather and interpret information from a distance, without physical interaction. It can be passive or active and has various applications, from weather satellites to electron microscopes. The inverse problem method is often used to derive desired results.
Remote sensing is a technique for obtaining information about something at a distance, without physical interaction. Digital remote sensing is a more refined version of this method that relies on advanced electronics to gather information and interpret it. This is distinct from conventional remote sensing which includes analog devices and basic methods such as visual perception or simply the act of looking at something.
Applications involving digital remote sensing can vary greatly in scope. Weather satellites and ultrasound machines are both types of remote sensing devices, for example, although the subjects of their scrutiny are wildly different. The important thing to remember is that scale is irrelevant when it comes to remote sensing. Its main advantage is the ability to obtain data on objects that are inaccessible or effectively immaterial, regardless of their size.
A magnetic resonance imaging (MRI) machine, for example, can scan the inside of the human body through the skin, eliminating the need for exploratory surgery in a large number of cases. Similarly, devices called photometers measure the amount of radiation emitted or reflected by distant objects, such as stars. Electron microscopes measure some of the smallest objects known to man, which otherwise could only be evaluated in large quantities.
Digital remote sensing, like remote sensing in general, can be divided into two main types: passive and active. A passive digital remote sensing device simply receives projected visual information from whatever subject it is observing. A digital camera is an example of a passive sensor, as it records the light radiated by an object and stores it.
Active digital remote sensing, in contrast, works by sending a signal that scans a subject and returns the results. Active sonar, which involves emitting sound waves and interpreting how they bounce off objects, is a type of active digital remote sensing. Another example is radar, which involves measuring the distance and direction of radio waves as they bounce off targets in their path.
In almost all cases of digital remote sensing, the information of interest cannot be measured directly. Instead, a principle known as an inverse problem is employed, whereby a known relative quantity is measured and used to derive the desired results. A prime example of this is how a police detective would evaluate tire tracks left at a crime scene to help determine what type of car may have been used in a robbery. Since there are no physical signs of the car itself, the inverse problem method uses a known quantity to draw a conclusion.
