Certified Photogrammetrist Digital Photogrammetry & Point Clouds 3

Question 1

What is 'voxel-based' point cloud processing?

Accepted Answer

Processing point clouds in a 3D grid of volumetric cells (voxels) for efficient spatial analysis

Answer

Voxel-based processing divides 3D space into a regular grid of volumetric cells (voxels), enabling efficient spatial indexing, subsampling, and analysis of large point clouds.

Question 2

In digital photogrammetry, what is 'epipolar geometry' used for?

Accepted Answer

Constraining image matching to a 1D search along epipolar lines, reducing computation and false matches

Answer

Epipolar geometry constrains the search for corresponding points to a one-dimensional line (epipolar line) in the second image, dramatically reducing computation and eliminating many false matches.

Question 3

What is the purpose of 'thinning' or 'decimating' a point cloud?

Accepted Answer

Reducing point cloud size by removing redundant points while preserving surface representation

Answer

Point cloud thinning/decimation reduces the number of points by removing redundant ones while preserving the essential shape and detail of the surface, making processing more manageable.

Question 4

In photogrammetric software, what does 'tie point extraction' (e.g., SIFT, SURF) accomplish?

Accepted Answer

Detecting distinctive image features and matching them across overlapping images for use in bundle adjustment

Answer

Algorithms like SIFT and SURF detect distinctive keypoints in images and match them across overlapping photos, creating the tie points used in bundle adjustment.

Question 5

What is 'photogrammetric restitution' in the context of digital mapping?

Accepted Answer

The process of extracting planimetric and topographic features from stereo imagery for map compilation

Answer

Photogrammetric restitution is the process of extracting map features—planimetric (roads, buildings) and topographic (contours, elevation)—from oriented stereo imagery for map production.

Certified Photogrammetrist Practice Test

Certified Photogrammetrist Practice Test

Certified Photogrammetrist Digital Photogrammetry & Point Clouds 3