PS Photogrammetry & Remote Sensing 2

Question 1

LiDAR (Light Detection and Ranging) determines distances by:

Accepted Answer

Recording the two-way travel time of emitted laser pulses and their returns

Answer

Measuring the intensity of backscattered solar radiation

Answer

Analyzing the Doppler frequency shift of emitted pulses

Answer

Comparing stereo images captured from two different sensor positions

Question 2

Ground Sample Distance (GSD) in aerial or satellite imagery is best described as:

Accepted Answer

The real-world size (area) of one image pixel as measured on the ground

Answer

The horizontal distance between consecutive ground control points

Answer

The horizontal spacing between successive LiDAR returns on the ground

Answer

The total ground area covered by a single flight line

Question 3

Which statement best describes passive remote sensing?

Accepted Answer

The sensor detects naturally available energy such as reflected solar radiation or thermally emitted energy from Earth's surface

Answer

The sensor emits energy and measures the signal reflected back from the target

Answer

The system operates only in darkness using artificial illumination from ground-based sources

Answer

The platform must be within 500 m of the target surface for effective data collection

Question 4

The primary purpose of aerial triangulation (aerotriangulation) is to:

Accepted Answer

Extend control from a sparse network of surveyed ground points to all photograph positions in the block

Answer

Measure vertical angles between ground control points on the ground

Answer

Calculate the flying height of the aircraft using onboard altimeters

Answer

Determine spectral calibration coefficients for each camera band

Question 5

Fiducial marks in a metric aerial camera are used to:

Accepted Answer

Define the interior photo coordinate system and locate the principal point for each exposure

Answer

Display the aircraft heading and altitude in the corner of each photograph

Answer

Indicate the boundaries of the stereo overlap zone between adjacent photos

Answer

Record the exact GPS time of exposure on the image frame for synchronization

Question 6

In LiDAR data processing, ground filtering (classification) is necessary because:

Accepted Answer

Returns from vegetation, buildings, and other above-ground features must be separated from bare-earth returns to generate an accurate DEM

Answer

Water surfaces absorb all laser energy and contaminate surrounding ground returns

Answer

Atmospheric refraction causes ground returns to appear at systematically incorrect elevations

Answer

The LiDAR scanner cannot distinguish between first and last pulse returns without post-processing filters

Question 7

A Digital Surface Model (DSM) differs from a Digital Terrain Model (DTM) in that a DSM:

Accepted Answer

Represents the elevation of the highest surface including vegetation canopy and building rooftops

Answer

Contains only spot elevations measured at surveyed benchmarks

Answer

Uses contour lines rather than a raster grid to represent elevation

Answer

Is generated exclusively from photogrammetric methods and not from LiDAR