#Radiant flux density how to

The arrows of different colour indicate that these two radiant flux densities are measured for all wavelengths present in the radiation field. On the right, exitance is the radiant flux leaving a surface per unit area. On the left, irradiance is the radiant flux incident on a surface per unit area. For practical use, the term irradiance is used to describe radiant flux density incident upon a surface, and exitance is used to describe radiant flux density leaving a surface (Figure 13).įigure 13: Irradiance and Exitance. This is called the radiant flux density, and is measured as radiant flux per unit area, for example W m -2. one represented by a pixel in a satellite image). In remote sensing, we are almost always interested in measuring the intensity of radiation over a finite area (e.g.

This is called radiant flux, and is measured in Joules per second, or Watts (W). Because radiation moves as the EMR waves propagate, an important measure of the intensity of an EMR field is the amount of energy moving onto, through or from a surface or volume per unit time. The fundamental SI unit of energy is the Joule (J). Several other properties of EMR fields relate to their intensity – the amount of energy contained in them.

#Radiant flux density how to

After that we will look at how to employ those concepts to extract useful information from satellite imagery. First we need to define some concepts related to electromagnetic radiation and how it is measured. In this chapter we will focus on such use of satellite imagery. cities and ships and fires, it is important to understand that most satellite sensors can also be thought of as precisely calibrated instruments used to measure the characteristics of electromagnetic radiation that arrives from a given direction at the time of measurement. While much remote sensing data can be visualized as imagery, and interpreted directly as such to locate e.g.