Remote Sensing & Satellite Imagery Flashcards

The Lyzenga log-ratio empirical method for satellite-derived bathymetry (SDB) is based on:

Answer: Logarithmic ratios of water-leaving radiance in two spectral bands calibrated with known depths

The Lyzenga method exploits the fact that different wavelengths attenuate at different rates with depth; by forming log-ratios of two bands and regressing against known control depths, a bathymetric model is derived.

What minimum spatial resolution is generally required for satellite imagery used in detailed coastal harbor feature mapping?

Answer: Sub-meter to 1 meter (Very High Resolution class)

Resolving fine coastal features such as dock edges, navigation aids, and channel margins requires sub-meter to 1-meter resolution imagery from very high resolution commercial satellites.

MODIS (Moderate Resolution Imaging Spectroradiometer) data is primarily used in hydrographic and oceanographic practice for:

Answer: Synoptic monitoring of ocean color, SST, and chlorophyll over large ocean areas

MODIS's 250 m–1 km resolution and 2,330 km swath make it ideal for large-scale, frequent monitoring of ocean color, sea surface temperature, sediment plumes, and chlorophyll-a concentrations.

Ground truth depth data is essential in satellite-derived bathymetry (SDB) because it is required to:

Answer: Calibrate the empirical spectral-to-depth model and validate its accuracy

SDB models (empirical or physics-based) must be calibrated using independently measured depths from sonar or other sources, and the resulting model must be validated against withheld check points.

Orthorectification of satellite imagery is performed to:

Answer: Remove geometric distortions caused by terrain relief displacement and sensor viewing geometry

Orthorectification uses a digital elevation model (or bathymetric model) and sensor parameters to correct for the apparent displacement of features caused by varying terrain elevation and off-nadir viewing angles.

Satellite radar altimetry contributes to hydrography and geodesy primarily by providing:

Answer: Sea surface height measurements used to model mean sea level and the marine geoid

Radar altimeters precisely measure sea surface height relative to a reference ellipsoid; these measurements underpin mean sea level determination, geoid modeling, and ocean circulation studies.

Which of the following satellite datasets is freely available and widely used for large-area coastal monitoring and satellite-derived bathymetry research?

Answer: Sentinel-2 (ESA Copernicus program)

Sentinel-2 imagery is freely accessible through the ESA Copernicus Open Access Hub, making it the most widely used dataset for large-area coastal change monitoring and shallow water bathymetry studies.