1.1 What is Remote Sensing?
So, what exactly is remote sensing? For the purposes of this tutorial,
we will use the following definition:
"Remote sensing is the science (and to some extent, art) of acquiring information about the Earth's surface without actually being in contact with it. This is done by sensing and recording reflected or emitted energy and processing, analyzing, and applying that information".
In much of remote sensing, the 
process involves an interaction between incident radiation and the targets of interest. This is exemplified by the use of imaging systems where the following seven elements are involved. Note, however that remote sensing also involves the sensing of emitted energy and the use of non-imaging sensors.
- Energy Source or Illumination (A) - the first
requirement for remote sensing is to have an energy
source which illuminates or provides electromagnetic
energy to the target of interest.
- Radiation and the Atmosphere (B) - as the
energy travels from its source to the target, it will come
in contact with and interact with the atmosphere it
passes through. This interaction may take place a
second time as the energy travels from the target to the
sensor.
- Interaction with the Target (C) - once the energy makes its way to the target through the atmosphere, it interacts with the target depending on the properties of both the target and the radiation.
- Recording of Energy by the Sensor (D) - after the energy has been scattered by, or emitted from the target, we require a sensor (remote - not in contact with the target) to collect and record the electromagnetic radiation.
- Transmission, Reception, and Processing (E)
- the energy recorded by the sensor has to be
transmitted, often in electronic form, to a receiving and
processing station where the data are processed into an
image (hardcopy and/or digital).
- Interpretation and Analysis (F) - the processed
image is interpreted, visually and/or digitally or
electronically, to extract information about the target
which was illuminated.
- Application (G) - the final element of the remote
sensing process is achieved when we apply the
information we have been able to extract from the
imagery about the target in order to better understand it,
reveal some new information, or assist in solving a
particular problem.
These seven elements comprise the remote sensing process from beginning to end. We will be covering all of these in sequential order throughout the five chapters of this tutorial,
building upon the information learned as we go. Enjoy the journey!
