GIS Geospatial Data Acquisition 3

Question 1

What does NDVI measure in remote sensing applications?

Accepted Answer

Normalized Difference Vegetation Index — plant health using NIR and red bands

Answer

NDVI uses the difference between near-infrared and red reflectance bands to quantify vegetation density and health, with values ranging from -1 to +1.

Question 2

Which orbital type do most civilian optical earth observation satellites use to ensure consistent illumination conditions?

Accepted Answer

Sun-synchronous orbit (SSO)

Answer

Sun-synchronous orbit keeps the satellite's orbital plane at a constant angle to the sun, ensuring each overpass occurs at the same local solar time for consistent lighting.

Question 3

In the context of GPS accuracy, what does 'selective availability' (SA) refer to?

Accepted Answer

An intentional degradation of civilian GPS accuracy formerly imposed by the US military

Answer

Selective Availability was a US Department of Defense policy that intentionally degraded civilian GPS accuracy; it was permanently disabled in May 2000.

Question 4

What is 'pansharpening' in satellite image processing?

Accepted Answer

Merging a high-resolution panchromatic image with lower-resolution multispectral bands to improve spatial detail

Answer

Pansharpening fuses a high-resolution single-band (panchromatic) image with lower-resolution multispectral bands to produce a color image with higher spatial resolution.

Question 5

A surveyor uses a total station to collect coordinates. What additional piece of equipment is needed to tie these measurements to a geodetic datum?

Accepted Answer

A GPS/GNSS receiver for control points

Answer

A GPS/GNSS receiver establishes control points with coordinates in a geodetic datum, which allows total station measurements to be referenced to a global coordinate system.

GIS - Geographic Information System Practice Test

GIS - Geographic Information System Practice Test

GIS Geospatial Data Acquisition 3