GISP Remote Sensing and Image Analysis 1 — Questions and Answers
Question 1: Which type of remote sensing uses its own energy source to illuminate a target and record the reflected signal?
- Passive remote sensing
- Active remote sensing (Correct answer)
- Thermal remote sensing
- Hyperspectral remote sensing
Correct answer: Active remote sensing
Active remote sensing systems, such as radar and LiDAR, emit their own electromagnetic energy and measure what is reflected back from the surface.
Question 2: What is the Normalized Difference Vegetation Index (NDVI) primarily used for in remote sensing?
- Measuring water depth
- Assessing vegetation health and density (Correct answer)
- Detecting urban heat islands
- Mapping soil moisture levels
Correct answer: Assessing vegetation health and density
NDVI is calculated from near-infrared and red band reflectance values to quantify vegetation density and health across a landscape.
Question 3: In Landsat 8 imagery, which band combination is most commonly used for a standard true-color composite?
- Bands 7-5-3
- Bands 5-4-3
- Bands 4-3-2 (Correct answer)
- Bands 6-5-4
Correct answer: Bands 4-3-2
A true-color composite assigns red, green, and blue wavelength bands (Bands 4, 3, and 2 in Landsat 8) to display colors as the human eye would perceive them.
Question 4: What does spatial resolution refer to in the context of satellite imagery?
- The number of spectral bands captured
- The smallest distinguishable ground feature size in an image (Correct answer)
- The frequency of satellite revisit time
- The radiometric bit depth of the sensor
Correct answer: The smallest distinguishable ground feature size in an image
Spatial resolution defines the smallest ground area that can be distinguished as a separate entity in an image, typically expressed as pixel size on the ground.
Question 5: Which atmospheric correction method converts raw digital numbers to surface reflectance by removing atmospheric effects using sensor-measured path radiance?
- Dark object subtraction (DOS) (Correct answer)
- Empirical line correction
- MODTRAN radiative transfer
- Histogram equalization
Correct answer: Dark object subtraction (DOS)
Dark object subtraction assumes that the darkest pixel in each band should have near-zero reflectance and uses it to estimate and remove atmospheric path radiance.
Question 6: What is the primary advantage of hyperspectral sensors over multispectral sensors?
- Wider swath coverage
- Higher spatial resolution
- Hundreds of narrow contiguous spectral bands enabling detailed material identification (Correct answer)
- Faster revisit times
Correct answer: Hundreds of narrow contiguous spectral bands enabling detailed material identification
Hyperspectral sensors capture hundreds of narrow, contiguous spectral bands, allowing identification of specific materials and chemicals by their unique spectral signatures.
GISP Remote Sensing and Image Analysis 1
Which type of remote sensing uses its own energy source to illuminate a target and record the reflected signal?