Certified Photogrammetrist Quality Control & Standards in Photogrammetry 2 — Questions and Answers
Question 1: What does 'logical consistency' mean in geospatial data quality standards (ISO 19157)?
- The agreement between the dataset and ground truth check points
- The degree to which a dataset conforms to its data model rules, including topological correctness and no invalid geometries (Correct answer)
- The consistency of radiometric values across the image mosaic
- The matching of feature attributes between different data sources
Correct answer: The degree to which a dataset conforms to its data model rules, including topological correctness and no invalid geometries
Logical consistency (ISO 19157) measures adherence to the data model's rules—such as polygon closure, no slivers, proper topology, and valid attribute values—independent of real-world accuracy.
Question 2: In photogrammetric production, what is a 'calibration certificate' for a metric camera?
- A flight plan approval document from aviation authorities
- A laboratory report documenting the camera's interior orientation parameters (principal distance, principal point, lens distortion) determined by calibration (Correct answer)
- A certificate confirming the camera operator's training qualifications
- An insurance document covering the aerial camera equipment
Correct answer: A laboratory report documenting the camera's interior orientation parameters (principal distance, principal point, lens distortion) determined by calibration
A calibration certificate documents the metric camera's interior orientation parameters—principal distance, principal point location, radial and decentering distortion—determined through laboratory calibration, essential for accurate photogrammetric processing.
Question 3: What is a 'flight report' in aerial photogrammetry production?
- A legal document filed with the FAA after each flight
- Documentation recording flight line numbers, photo numbers, exposure stations, weather conditions, and quality observations during data acquisition (Correct answer)
- The output accuracy report from bundle adjustment processing
- A summary of the project's financial expenditures
Correct answer: Documentation recording flight line numbers, photo numbers, exposure stations, weather conditions, and quality observations during data acquisition
A flight report documents all relevant information about the data acquisition flight—including flight lines, photo numbers, GPS positions, weather conditions, and any anomalies—supporting project documentation and quality review.
Question 4: What is 'stereo compilation QC' (quality control) typically checking for?
- Correct color calibration of the stereo display monitor
- Feature completeness, geometric accuracy, attribution correctness, edge match quality, and adherence to project specifications (Correct answer)
- The operator's correct use of the floating mark height adjustment
- That all tie points are visible in at least three images
Correct answer: Feature completeness, geometric accuracy, attribution correctness, edge match quality, and adherence to project specifications
Stereo compilation QC reviews the compiled map features for completeness, geometric accuracy relative to the imagery, correct attribution, seamless edge matching between models, and conformance to the project's feature and accuracy specifications.
Question 5: What does 'positional accuracy' mean in the ASPRS/FGDC standards context?
- The qualitative description of a dataset's fitness for a specific use
- The closeness of the reported positions of features to their true positions on the Earth's surface (Correct answer)
- The pixel-level sharpness of the orthophoto product
- The alignment between GPS-collected and photogrammetrically derived features
Correct answer: The closeness of the reported positions of features to their true positions on the Earth's surface
Positional accuracy (per ASPRS/FGDC) is the closeness of the reported coordinates of geographic features to their true positions, typically measured by RMSE against independently surveyed check points.
Question 6: What is the purpose of 'independent QC' (third-party accuracy testing) in photogrammetric projects?
- To reduce the cost of data collection by outsourcing accuracy testing
- To provide an unbiased assessment of accuracy by an organization not involved in data production (Correct answer)
- To verify that the client's software can read the delivered file formats
- To confirm that image overlap meets the specified requirements
Correct answer: To provide an unbiased assessment of accuracy by an organization not involved in data production
Independent QC uses a third party not involved in production to collect and analyze check points, providing an unbiased accuracy assessment free from the production organization's potential self-reporting bias.
Certified Photogrammetrist Quality Control & Standards in Photogrammetry 2
What does 'logical consistency' mean in geospatial data quality standards (ISO 19157)?