Stereo Compilation & 3D Modeling Flashcards

What is the 'y-parallax' in a stereopair, and what does excessive y-parallax indicate?

Answer: Residual vertical displacement after relative orientation; it indicates incomplete relative orientation

Y-parallax is residual vertical displacement of conjugate points in a stereopair after relative orientation; excessive y-parallax indicates that the relative orientation is incomplete or incorrect.

In stereo compilation, what does 'absolute orientation' accomplish?

Answer: It scales, rotates, and positions the stereomodel into a real-world coordinate system using ground control

Absolute orientation transforms the relatively oriented stereomodel (which exists in an arbitrary coordinate system) into real-world coordinates using ground control points.

What is 'x-parallax' used for in stereo photogrammetry?

Answer: Measuring elevation differences between points in a stereopair

X-parallax (the horizontal displacement between corresponding points in a stereopair) is directly related to the elevation of those points and is the fundamental measurement used for height determination.

What is a 'floating mark' in analogue or softcopy stereo compilation?

Answer: A stereoscopic measuring mark that appears to float at a selected elevation within the stereomodel

A floating mark is a stereoscopic measuring reticle that the operator perceives as resting on the terrain surface when the parallax is correctly set, used to measure or compile terrain features.

What are the six elements of exterior orientation for a single photograph?

Answer: X, Y, Z (position of perspective center) and ω, φ, κ (three rotation angles)

Exterior orientation consists of six parameters: three for the position of the perspective center (X₀, Y₀, Z₀) and three rotation angles (omega ω, phi φ, kappa κ) defining the camera's attitude.

What is the 'base-to-height ratio' (B/H ratio) in aerial stereophotogrammetry?

Answer: The ratio of the air base (distance between exposure stations) to the flying height, affecting depth measurement sensitivity

The base-to-height ratio (B/H) is the ratio of the air base to the flying height; a larger B/H ratio increases the sensitivity of parallax-based height measurements but also increases relief displacement.