Remote Sensing Foundations I: Quarks to Spectra
Question: I’m not sure I understand amplitude when it comes to wave energy. As I understand it, amplitude is the height of a wave, and higher amplitude means higher energy. But on the slides (the one with the equations and the one with the EM spectrum) — energy relates to frequency and wavelength. How does amplitude figure in? Are high frequency/low wavelength waves also high amplitude?
Instructor Answer: To put it simply: Yes, amplitude and energy are directly related. The higher the amplitude, the higher the energy that is prompted. Amplitude is the size of the wave, from its peak. That being said, there are 2 ways to change it; movement or distance a.k.a. frequency and wavelength. You can have high amplitude and low frequency by increasing wavelength.
Imagine beating a drum at a constant rate, say 60 bpm or one beat per second. Now without hitting the drum any harder, double your rate to 120bpm or two beats per second. Your energy has doubled without your amplitude increasing – your frequency has doubled, wavelength halved, but each wave isn’t carrying more energy. Now go back to one beat per second, but hit the drum twice as hard. Now your energy has doubled without changing frequency, and each wave (or beat) is double the original amplitude, and carrying twice the amount of energy. So basically, energy increase is not necessarily uni-directional.
Question: Quarks: The video starts out talking about quarks and their importance of understanding energy. When it gets to the electromagnetic spectrum, you mention photon energy. What are we actually measuring when we sense electromagnetic radiation — energy at the quark level, the photon level, something else, all of the above? What’s the role of quarks when we’re doing remote sensing?
Instructor Answer: Electromagnetic radiation has to do more with energy from Photons directly. I think you are confusing the role that quarks and photons have in this case. Remember that electromagnetic fields and photons are really just relating to the same phenomena. Quarks are simply electrically charged so that’s why they interact with magnetic fields. Also remember that Quarks are not actually able to be observed because of color confinement. Understanding quarks simply helps with understanding concepts that have to do with remote sensing. Don’t think too hard in relation to remote sensing yet! These are just building blocks to help understand the functions of remote sensing down the line.
For Google Earth Engine — the video by Dave Thau says it’s free to use for non-commercial applications. In your experience, does that include university research? I would think so, but you never know.
Google Earth engine is free.