Study Guide Flashcards
What is Atmospheric Window and Why is it important for RS?
A spectrum portion outside the main absorbtion bands of the atmospheric gases that can be used for remote sensing.
Size
Relative and/or absolute size of an object relative to other objects in a sceneq
What is multi-band image display?
Viewing multiple bands. Relies on color mixing to display.
Reflectance
Portion of the incident energy on a surface that is reflected, usually expressed as a percentage. Spectral reflectance is the reflectance as a function of wavelength. Also can be expressed as a ration with a value range of 0 to 1 and then occasionally called reflectivity.
What is the WRS2 system?
Worldwide Reference System. Global notation for landsat data. Path and Row numbers uniquely identify a nominal scene center. WRS 2 is on Landsate 4-8.
Tradeoffs among four types of resolution (Give example)
Depending on how greater or lower resolution is achieved, it can have an effect. If temporal resolution is increased by widening the swath, it will result in reduced spatial resolution. An increase in spatial resolution may require a smaller field of view, which means a sensor will take in less light, leading to reduced radiometric resolution. To increase spatial resolution without decreasing radiometric resolution, it would require increasing the length of a band which a sensor detects leading to a reduction in spectral resolution.
What is largest number of pixels an 8-bit image can store?
256 - 0 to 255
What are platforms and what kinds are there in RS?
A vehicle, such as a satellite or aircraft used to carry a sensor.
General Concepts of Radiation Law
In the wave theory of electromagnetic radiation, radiation moves as an electromagnetic wave consisting of an electrical save and a magnetic wave, which is at a 90 degree angle from the electrical wave. These two fields oscillate as waves. When the electrical wave has a positive energy, the magnetic wave has a negative energy and vice-versa.
Electromagnetic waves travel at the speed of light.
Wavelength is the length of a wave cycle measured as the difference between wave crests. Frequency refers to the number of cycles per unit of time.
The speed of light = wavelength x frequency, so in order to maintain the constant speed of light, wavelength and frequency or inversely related. Shorter the wavelength the higher the frequency.
Frequency is related to energy. Higher frequency = higher energy.
Amplitude is the difference between crest of wave and the “center line”. Amplitude can be different for same wavelength. Describes intensity.
What is the principle when choosing a band composite to differentiate land objects?
Example, natural grass and artificial turf
Pushbroom vs Whiskbroom Scanner
Whisk broom scanner is an across-track scanner. Pushbroom scanner is along-track scanner. Whisk broom scanners use a rotating mirror to scan from side to side to focus on light from different areas on the ground. Pushbroom Scanner uses an array of sensors.
What is a reflectance curve?
Curve showing the portion of the incident energy that is reflected by a material as a function of wavelength. IE what wavelengths will be reflected by different materials.
Definition of Remote Sensing
The art, science and technology of observing and object, scene, or phenomenon by instrument-based techniques. Remote is because the observation is done at a distance without physical contact with the object.
Temporal Resolution
Amount of time needed to revisit the same location.
What is single-band image display?
Displaying only the image captures for a single band.
What is a pixel?
Picture element. Building cell of a digital image. Smallest non-divisible elemetn of a digital image. Value of a pixel can be called Pixel value, brightness value, digital number, etc.
Brief History of Remote Sensing
Begins with photograph in 1820s. The practical applications of photography expanded with technology, beginning with photogrammetry, taking aerial pictures to produce topographic maps. At first using balloons in 1858, kites in 1882, rockets in 1897, pigeons in 1903, and the airplanes in 1909, finally progressing to satellites in the space era.
Moreover, the ability of what types of electromagnetic energy that can be captures by a camera or sensor expanded from visible light, to thermal infrared in the early 1900s, and eventually the rest of the EM Spectrum.
Many applications for this technology were general mapping and military in nature originally, but have expanded over time to more civilian uses such as meteorology
When is Mie Scattering Likely to Occur?
When particles that are about the same size as the wavelength, which effects longer wavelengths.
Texture
Arrangement and frequency of tonal variations in particular areas of an image. Rough texture would be where grey levels change abruptly in small areas. Smooth areas are the result of uniform, even surfaces, such as fields or asphalt
Difference between multispectral and hyperspectral?
Multispectral scanning is remote sensing technique in which the Earth’s surface is scanned and reflected radiation is recorded simultaneously in different wavelength bands.
Multispectral scanners can measure several bands of the EM Spectrum at the same time. A hyperspectral scanner has an even higher spectral resolution with no gaps in spectral coverage. A multispectral scanner might record data for up to 12 bands whereas hyper can record hundreds of bands.
Types of Scattering
Rayleigh
Mie
Nonselective
