Remote Sensing & Image Interpretation Flashcards

Which formula correctly defines the Normalized Difference Vegetation Index (NDVI)?

Answer: (NIR − Red)/(NIR + Red)

NDVI normalizes the difference between near-infrared and red reflectance, yielding values from −1 to +1.

The strong near-infrared reflectance of healthy green leaves is primarily caused by what?

Answer: Internal scattering by the spongy mesophyll cell structure

Multiple scattering at cell wall–air interfaces in the spongy mesophyll produces high NIR reflectance.

Which wavelength range is the primary atmospheric window used for thermal infrared sensing of Earth surface temperatures?

Answer: 8–14 µm

The 8–14 µm window has low atmospheric absorption and contains the peak emission of objects near Earth's ambient temperature.

Rayleigh scattering, which causes haze in aerial imagery, affects which wavelengths most strongly?

Answer: Blue

Rayleigh scattering is inversely proportional to the fourth power of wavelength, so shorter blue wavelengths scatter most.

What is the spatial resolution of the panchromatic band on the Landsat 8/9 OLI sensor?

Answer: 15 m

OLI band 8 (panchromatic) has 15 m resolution, while its multispectral bands are 30 m.

A sensor with 12-bit radiometric resolution can record how many distinct brightness levels?

Answer: 4,096

Radiometric levels equal 2 raised to the bit depth, so 2¹² = 4,096.

In standard color-infrared (false-color) aerial imagery, healthy vegetation typically appears as what color?

Answer: Red

CIR imagery displays NIR as red, so vegetation's high NIR reflectance renders it red.

Which element of image interpretation is most useful for estimating the height and profile of a tall structure on a vertical aerial photo?

Answer: Shadow

Shadows reveal an object's side profile and, with sun angle, allow height estimation.

In image interpretation, 'texture' is best defined as what?

Answer: The frequency of tonal change within an area

Texture describes the fineness or coarseness produced by tonal variation too small to discern individually.

Identifying a building as a high school because it is adjacent to a running track and football field uses which interpretation element?

Answer: Association

Association uses related nearby features to identify an object.

Vertical exaggeration in stereoscopic viewing of aerial photos occurs mainly because of what?

Answer: The air base-to-flying height ratio exceeds the viewer's eye base-to-viewing distance ratio

When B/H of the photography is larger than the equivalent viewing ratio, relief appears exaggerated.

On a truly vertical aerial photograph, relief displacement of a tall object occurs in which direction?

Answer: Radially outward from the nadir point

Relief displacement is radial from the nadir, with tops displaced outward for objects above datum.

Using relief displacement on a vertical photo, object height h is calculated by which equation (d = displacement, r = radial distance to top, H = flying height above base)?

Answer: h = d·H/r

Height equals displacement times flying height divided by the radial distance from nadir to the object's top.

Regularly spaced rows of trees that identify an orchard are an example of which interpretation element?

Answer: Pattern

Pattern is the spatial arrangement of objects, such as the grid spacing of orchard trees.

In side-looking SAR imagery, layover occurs when which condition is met?

Answer: The slope facing the radar is steeper than the local incidence angle

When foreslope exceeds the incidence angle, the top returns before the base and is imaged closer to the sensor.

The grainy 'salt-and-pepper' appearance in SAR imagery is called speckle and is commonly reduced by what?

Answer: Multi-look processing or adaptive filtering

Speckle comes from coherent interference and is reduced by averaging independent looks or speckle filters.

Sentinel-1 and RADARSAT operate in C-band, which has a wavelength of approximately what?

Answer: 5.6 cm

C-band SAR wavelength is about 5.6 cm (roughly 3.75–7.5 cm range).

Which radar band offers the greatest penetration into forest canopy among these options?

Answer: L-band

Longer wavelengths like L-band (~23 cm) penetrate foliage further than shorter bands.

In predawn thermal infrared imagery, water bodies typically appear how relative to surrounding dry land?

Answer: Warmer (brighter)

Water's high thermal capacity keeps it warmer than land, which cools quickly overnight.

Using Wien's displacement law, an Earth surface at about 300 K has peak emission near which wavelength?

Answer: 9.7 µm

Peak wavelength ≈ 2898 µm·K / 300 K ≈ 9.7 µm.