Lab4b_RemoteSensingand_Digital_Images (4)

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Red Rocks Community College *

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Astronomy

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Oct 30, 2023

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Lab 4b: Remote Sensing & Digital Images (46pts) 1. (2) What is the definition of remote sensing? Remote sensing is a technique used to collect information about an object or area from a distance, typically using aerial photographs or satellite images. 2. (4) As this is the primary method we use to investigate and explore our universe, what limitations make it necessary to use this method? The primary limitation of using telescopes to explore the universe is their limited field of view. Telescopes can only observe a small portion of the sky at any given time, meaning they can only observe a small portion of the universe. Additionally, the amount of light that telescopes can detect is limited. Telescopes can only detect light that is within a certain range of wavelengths, meaning they can only detect certain forms of radiation. Finally, the resolution of telescopes is limited, meaning they can only detect objects of a certain size. 3. (6) Think about how these limitations might be overcome and suggest viable solutions for overcoming two of them. Be specific and detailed. 1. Increasing the Aperture Size: To increase the field of view of a telescope, the aperture size of the telescope needs to be increased. This means increasing the diameter of the telescope's optics, such as its mirror or lens, to allow it to capture more light from a wider area of the sky. This can be done by using larger and more powerful mirrors or lenses. 2. Combining Telescopes: Another way to overcome the limited field of view of a telescope is to combine multiple telescopes into an array. By using a technique called interferometry, multiple telescopes can be combined to act as a single instrument, providing a wider field of view than any of the individual telescopes. This technique is often used with radio telescopes but can also be used with optical telescopes.

4. (4) Describe what the electromagnetic spectrum is and give some examples of EMS energy. The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. Examples of electromagnetic spectrum (EMS) energy include gamma rays, X- rays, ultraviolet radiation, visible light, infrared radiation, and radio waves. 5. (3) Research how wavelength, frequency and the speed of light are related and provide an equation. Wavelength, frequency, and the speed of light are related by the following equation: Speed of Light (c) = Wavelength (λ) x Frequency (f) This equation is also known as the wave equation and states that the speed of light is equal to the product of the wavelength and frequency of the light wave. This equation is a fundamental physical law for all electromagnetic radiation and is derived from Maxwell's equations. 6. (4) What is a reflectance curve and why is it important to Remote Sensing? A reflectance curve is a graph that shows how much light is reflected by a surface at different wavelengths of light. This is important to remote sensing because it allows us to characterize the reflectance of different materials and surfaces, which can be used to identify or classify objects from a distance. For example, vegetation and water can be distinguished from each other by their reflectance curves, allowing for more accurate mapping and monitoring. 7. (5) If you were to build an instrument to monitor the Earth’s surface in three discrete wavelengths (I want wavelength numbers here not regions like the UV region) where

might you suggest they be placed along the EMS? (Hint: use the atmospheric transmission plot at the end of the lab) Why? The three wavelengths that could be used to monitor the Earth's surface are: 1. 940nm 2. 730nm 3. 550nm These wavelengths can be selected based on the atmospheric transmission plot at the end of the lab. 940nm is in the near- infrared region and has high transmission, so it is ideal for monitoring the earth's surface. 730nm is in the visible region and has high transmission, so it is also suitable for monitoring the earth's surface. 550nm is in the blue region and has medium transmission, so it can also be used to monitor the earth's surface. 8. (5) Where wouldn’t you want those 3 bands to be and for what reasons? Identify the molecules that would interfere with the transmission at the wavelengths you chose. I wouldn’t want the 3 bands to be near a dense cloud of water vapor, carbon dioxide, oxygen, ozone, or nitrogen dioxide. These molecules would interfere with transmission at the wavelengths chosen because they can absorb energy at the same wavelengths. 9. (2) How is a digital image different from a photograph? A digital image is an image that is created and stored electronically, while a photograph is an image that is created on light-sensitive paper. Digital images are often more easily manipulated than photographs and can be composed and edited more quickly. Additionally, digital images can be stored, shared, and printed more easily than photographs. 10. (2) Describe the components of a digital image. A digital image is composed of several components.

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1. Pixels: Pixels are the smallest unit of a digital image and are the building blocks of digital images. Each pixel is a single color or shade, and the combination of all pixels forms the full image. 2. Resolution: Resolution measures how much detail a digital image contains. It is measured in dots per inch (DPI) or pixels per inch (PPI). The higher the resolution, the more detailed and sharper the image appears. 3. Color Depth: Color depth is the number of bits used to store color information for each pixel. The higher the color depth, the more colors the image can contain. 4. Compression: Compression is a process used to reduce the size of a digital image. It removes redundant information and reduces the file size, but it can also reduce the quality of the image. 5. File Format: File formats are the types of files used to store digital images. Common file formats include JPEG, GIF, and PNG. 11. (2) What two things made the invention of the digital camera/image such a powerful tool for studying the Solar System, Galaxies and Universe? 1. The digital camera/image was able to capture incredibly detailed images of astronomical objects, allowing researchers to study them in a way not possible with analog cameras. 2. The digital camera/image was able to take multiple exposures and combine them together, allowing researchers to gather a much more complete picture of astronomical objects. 12. (2) Why are color images a more powerful tool than B&W images? Color images are more powerful than black and white images because they can convey more information in a single glance. Colors evoke strong emotions and create a sense of connection with the audience. Colors can also be used to create contrast, depth, and visual interest. Furthermore, color images are more visually appealing and can draw attention to the subject of the image more easily.

13. (4) What are false-color images and how do they provide more information than true- color images? False-color images are images that have been digitally altered to represent different colors than those that are actually present in the scene. These images are typically used to enhance features or provide better contrast between objects in the image. False-color images can provide more information than true-color images because they can highlight features that may be difficult to distinguish in a true-color image. For example, in a false-color satellite image, different vegetation types may be easier to identify because they are represented by different colors. 14. (1) If you are interested in mapping vegetation on the Earth’s surface, at what wavelength would you want your instrument to record the reflectance of the Earth’s surface (this can be approximate)? The most useful wavelengths for vegetation mapping are the near-infrared (NIR) wavelengths of around 0.7 - 0.9 micrometers. Figure 1. Atmospheric Transmission plot.