CH Remote Sensing & Satellite Imagery 2

Question 1

Converting raw satellite digital number values to surface reflectance is accomplished through:

Accepted Answer

Radiometric calibration followed by atmospheric correction

Answer

Radiometric calibration converts raw digital numbers to at-sensor radiance, and atmospheric correction then removes the effects of atmospheric scattering and absorption to yield true surface reflectance.

Question 2

ICESat-2, used for shallow water depth mapping, employs which primary technology?

Accepted Answer

Photon-counting green-wavelength LiDAR (ATLAS instrument)

Answer

ICESat-2 carries the Advanced Topographic Laser Altimeter System (ATLAS), a photon-counting LiDAR using 532 nm green light capable of penetrating shallow, clear water to measure bathymetry.

Question 3

What is the primary limitation of optical satellite imagery when used for bathymetric surveys?

Accepted Answer

Water turbidity and depth restrict usable optical penetration

Answer

Suspended sediment, algae, and colored dissolved organic matter absorb and scatter light rapidly, limiting optical satellite bathymetry to clear, shallow water typically shallower than 20–25 m.

Question 4

WorldView-2 is particularly valuable for coastal bathymetric mapping because it provides:

Accepted Answer

Eight multispectral bands including a coastal blue band with sub-meter panchromatic resolution

Answer

WorldView-2's eight spectral bands — including the 400–450 nm coastal blue band ideal for water penetration — combined with approximately 0.5 m panchromatic resolution make it well suited for high-detail shallow water mapping.

Question 5

In multispectral satellite-derived bathymetry, which wavelength range penetrates deepest into clear oceanic water?

Accepted Answer

Blue band (~450 nm)

Answer

Water absorbs longer wavelengths (red, near-infrared) very rapidly; blue light (~450 nm) experiences the least absorption in clear oceanic water and therefore penetrates to the greatest depth.

(CH) Certified Hydrographer Practice Test

(CH) Certified Hydrographer Practice Test

CH Remote Sensing & Satellite Imagery 2