Scan Geometry Effects in Satellite Imaging Which statements correctly describe geometric and resolution effects as the sensor scans away from nadir?

Introduction / Context:
Across-track (whiskbroom) and pushbroom imagers both experience geometric effects away from nadir. Understanding how instantaneous field of view (IFOV) projects on the ground and how perspective alters feature shape is crucial for interpreting imagery and for pre-processing steps such as orthorectification.

Given Data / Assumptions:

• Nadir is the point directly beneath the sensor; theta is the off-nadir scan angle.
• Flat Earth assumption locally for intuition; true processing uses Earth curvature and ephemeris.
• IFOV is small enough that first-order projections apply.

Concept / Approach:

As the look angle increases, the ground-projected size of a fixed angular IFOV grows due to obliquity. Along one dimension this scales roughly as sec(theta), and the projected area scales approximately as sec^2(theta). Simultaneously, perspective causes panoramic distortion: features toward the scan edge are geometrically compressed in one direction while stretched in others, and relief displacement increases.

Step-by-Step Solution:

Verification / Alternative check:

Sensor geometry models in orthorectification software implement these relations and remove compressions through resampling using accurate ephemeris and DEMs.

Why Other Options Are Wrong:

“None” contradicts observed imagery and sensor design notes.

Common Pitfalls:

Assuming constant GSD across the swath; ignoring angular dependence when comparing edge and centre radiometry; confusing linear dimension scaling with area scaling.

Final Answer:

All of these