Certified Photogrammetrist Digital Photogrammetry & Point Clouds

Question 1

What algorithm is most commonly used for automatic image matching to generate dense point clouds?

Accepted Answer

Semi-Global Matching (SGM) or Multi-View Stereo (MVS)

Answer

RANSAC feature rejection only

Answer

Kriging interpolation

Answer

Inverse distance weighting

Question 2

What is 'ground sample distance' (GSD) in digital photogrammetry?

Accepted Answer

The real-world size represented by one pixel in the image

Answer

The distance between GPS ground control points

Answer

The spacing between flight lines

Answer

The minimum detectable elevation difference

Question 3

Which type of point cloud classification separates ground returns from vegetation and structures?

Accepted Answer

LAS class 2 (ground) filtering using algorithms like Progressive TIN or CSF

Answer

Radiometric classification

Answer

K-means spectral clustering

Answer

Principal component analysis

Question 4

What is a Structure from Motion (SfM) workflow in photogrammetry?

Accepted Answer

A process that reconstructs 3D structure and camera positions simultaneously from unordered image sets

Answer

A method for generating animated fly-throughs

Answer

A radiometric correction technique for haze removal

Answer

A film scanning workflow for analog photography

Question 5

In a LiDAR or photogrammetric point cloud, what does 'point density' measure?

Accepted Answer

The number of points per unit area (e.g., points per square meter)

Answer

The color saturation of each point

Answer

The vertical accuracy of individual points

Answer

The compression ratio of the LAS file

Question 6

What is 'image radiometric normalization' used for in digital photogrammetry?

Accepted Answer

Adjusting image brightness and color consistency across a mosaic to reduce seam visibility

Answer

Converting image coordinates to geographic coordinates

Answer

Increasing the focal length of the camera digitally

Answer

Removing geometric distortion caused by lens aberrations