Lecture 3 Flashcards
(22 cards)
What is spectral resolution?
The ability of a sensor to distinguish between different wavelengths of electromagnetic radiation.
What are spectral bands?
Discrete wavelength intervals used to collect image data in specific portions of the electromagnetic spectrum.
What is the difference between low and high spectral resolution?
Low spectral resolution captures broad bands (e.g., RGB), while high spectral resolution includes narrow bands (e.g., NIR, SWIR) for detailed analysis.
What is a spectral signature?
A feature’s unique pattern of reflected energy across spectral bands.
What is spectral enhancement?
A technique to create new image data using pixel operations between spectral bands to highlight specific features.
Name three common spectral enhancement techniques.
1) Spectral Ratios & Indices, 2) Principal Components Analysis (PCA), 3) Tasseled Cap Transformation.
What does PCA do in spectral enhancement?
Compresses redundant data into fewer, more informative bands for analysis.
What is NDVI and what does it measure?
Normalized Difference Vegetation Index; it measures vegetation health using NIR and Red bands. Formula: (NIR - Red) / (NIR + Red)
What is NDMI used for?
To monitor moisture in vegetation; indicates drought or fuel levels. Formula: (NIR - SWIR1) / (NIR + SWIR1)
What is NDBI and what does it detect?
Normalized Difference Built-up Index; used to detect built-up urban areas. Formula: (SWIR - NIR) / (SWIR + NIR)
What does NDWI indicate?
Presence and changes in surface water content. Formula: (Green - NIR) / (Green + NIR)
What is spatial resolution?
The size of a pixel on the ground; it determines image detail.
How is spatial resolution related to pixel size?
Smaller pixels = higher spatial resolution (more detail).
Define GIFOV.
Ground Instantaneous Field of View – the ground area covered by a single detector.
What happens to pixel size at large scan angles (e.g., AVHRR)?
Pixel size increases due to sensor angle and Earth curvature.
What is spatial enhancement?
Techniques to improve image detail and clarity.
Name four spatial enhancement techniques.
1) Spatial filtering, 2) Pan-sharpening, 3) Edge enhancement, 4) Super-resolution.
What is pan-sharpening?
Merging high-res panchromatic and low-res multispectral images to get high-res multispectral imagery.
What is spatial filtering?
Applying kernels to highlight or suppress image features.
What does a high-pass (high-frequency) kernel do?
Enhances edges by increasing spatial frequency.
What does a low-pass (low-frequency) kernel do?
Smooths the image by reducing spatial frequency and averaging pixel values.
What is the main difference between spectral and spatial resolution?
Spectral = number & width of bands; Spatial = pixel size/detail in the image.
