GIS Geospatial Data Acquisition 5

Question 1

What is the 'revisit time' (or repeat cycle) of a remote sensing satellite?

Accepted Answer

The time between successive passes over the same geographic location

Answer

Revisit time is the interval between two consecutive observations of the same location by the same satellite, which determines how often up-to-date imagery can be collected.

Question 2

In terrestrial laser scanning (TLS), what is a 'scan registration' or 'point cloud registration'?

Accepted Answer

Aligning multiple individual scan positions into a single unified coordinate system

Answer

Registration combines multiple point cloud scans collected from different positions into one coherent dataset with a common coordinate system, typically using overlapping points or targets.

Question 3

What is 'image orthorectification' and when is it necessary?

Accepted Answer

Correcting geometric distortions caused by terrain relief, sensor tilt, and Earth's curvature to create a planimetrically accurate map

Answer

Orthorectification removes distortions from relief displacement and sensor geometry, producing an orthophoto where every pixel represents a true planimetric position suitable for accurate spatial measurements.

Question 4

What is 'GNSS augmentation' and what systems provide it in the United States?

Accepted Answer

Using additional reference signals to improve GNSS accuracy; WAAS (Wide Area Augmentation System) is the primary US provider

Answer

GNSS augmentation uses ground reference stations and geostationary satellites to broadcast correction signals; WAAS provides sub-meter accuracy to compatible receivers across North America.

Question 5

What is 'hyperspectral imaging' and how does it differ from standard multispectral imaging?

Accepted Answer

Hyperspectral captures hundreds of narrow, contiguous spectral bands; multispectral captures only a few broad bands

Answer

Hyperspectral sensors collect data in hundreds of narrow, contiguous spectral bands, enabling detailed material identification, while multispectral sensors typically collect only 4-12 broader spectral bands.

GIS - Geographic Information System Practice Test

GIS - Geographic Information System Practice Test

GIS Geospatial Data Acquisition 5