Midterm Review

Question 1

What factors affect image distortion?

Answer 1

1. Tip & Tilt
2. Height Displacement
3. Lens Distortion
4. Curvature of the Earth
5. Atmospheric Refraction

Question 2

Of the 5 causes for image distortion, which two major impacts?

Answer 2

1. Tip & Tilt
2. Height Displacement

Question 3

What are the core components of a UAS?

Answer 3

1.Propulsion System (typically)
2.Navigation System
3.Autopilot
4.Wireless Communication

Question 4

What does SIFT stand for?

Answer 4

Scale-Invariant Feature Transform

Question 5

What is Aerial Triangulation?

Answer 5

Aerial triangulation (AT) is the process of aligning common tie points between overlapping photos to create a photo mosaic. AUTOMATICALLY!

Question 6

What is an orthophoto?

Answer 6

Orthophotos are flat, 2-D seamless mosaics where all the photos have been seamlessly merged together, color balanced with radial and elevation distortions removed.

Question 7

What is the difference between LiDAR and PhoDAR?

Answer 7

**LiDAR: **Light Detection and Ranging – uses a RANGING Device (Laser – Class1 EyeSafe)
DIRECT OBSERVATION of 3D Coordinate (discrete range & angle solution)
SINGLE Light Ray originating from Scanners Own Coordinate System (SOCS)
Requires DIRECT GEOREFERENCING – Position and Orientation Solution

**“PhoDAR”: **(or photogrammetrically derived Point-Cloud) derived from Structure from Motion
INDIRECT OBSERVATION as 3D Point Cloud is mathematically re-constructed from multiple intersecting Light Rays from multiple vantage points (overlap/multiple photos).