Remote Sensing & Satellite Imagery Flashcards

What does LiDAR stand for in the context of hydrographic remote sensing?

Answer: Light Detection And Ranging

LiDAR stands for Light Detection And Ranging, using laser pulses to measure distances and, in bathymetric applications, water depths.

Which type of satellite sensor is most commonly used to measure sea surface temperature (SST) in hydrographic studies?

Answer: Thermal Infrared (TIR) sensor

Thermal infrared sensors detect heat emission from the ocean surface, making them the standard tool for sea surface temperature measurement from satellites.

What is the primary advantage of multispectral satellite imagery for shallow water bathymetry?

Answer: It can penetrate clear, shallow water to map the seafloor using light attenuation

Multispectral imagery exploits differential attenuation of light wavelengths through clear water, enabling seafloor mapping in shallow, transparent conditions typically up to 20–25 m depth.

Synthetic Aperture Radar (SAR) is particularly valuable for hydrographic applications because it can:

Answer: Detect oil spills, ship wakes, and surface roughness regardless of cloud cover or darkness

SAR operates in the microwave spectrum, penetrating clouds and functioning day or night, making it ideal for detecting surface phenomena such as oil spills, ship wakes, and internal waves.

The Secchi depth is used in satellite-derived bathymetry primarily to estimate:

Answer: Water transparency and maximum depth of optical light penetration

Secchi depth quantifies water transparency by measuring how deep a white disk remains visible, indicating how far light penetrates and thus the practical depth limit for optical satellite bathymetry.

The Normalized Difference Water Index (NDWI) is primarily used in remote sensing to:

Answer: Distinguish and delineate water bodies from land and vegetation

NDWI uses the ratio of green and near-infrared bands to highlight water bodies, since water strongly absorbs NIR while land and vegetation reflect it strongly.

Which orbit type do most hydrographic Earth observation satellites use to achieve consistent global coverage?

Answer: Sun-synchronous Low Earth Orbit (LEO)

Sun-synchronous LEO orbits ensure the satellite crosses each latitude at the same local solar time, providing consistent illumination conditions and global coverage with frequent revisits.