Certified Photogrammetrist Exam — Questions and Answers

Question 1: What is 'photogrammetric restitution' in the context of digital mapping?

Reconstructing damaged photographs from partial data
The process of recovering financial costs from project overruns
Recovering deleted project files from backup storage
The process of extracting planimetric and topographic features from stereo imagery for map compilation (Correct answer)

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

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

Question 2: In photogrammetric sensor calibration, what is meant by 'self-calibration'?

Calibration performed using only onboard GPS/IMU data without ground control
The manufacturer pre-calibrates the sensor before delivery to the client
The camera automatically adjusts its parameters during flight
Camera interior orientation parameters are solved simultaneously with exterior orientation during bundle adjustment using object-space control (Correct answer)

Correct answer: Camera interior orientation parameters are solved simultaneously with exterior orientation during bundle adjustment using object-space control

Self-calibration (on-the-job calibration) simultaneously solves for interior orientation parameters and exterior orientation parameters within the bundle adjustment, using highly redundant imagery and ground control points.

Question 3: What is 'nadir' in aerial photogrammetry?

The point on the photograph with minimum distortion due to radial lens distortion
The principal point of the camera calibration
The highest point in the flight block
The point on the ground directly below the camera's perspective center (ground nadir), or its image (photo nadir) (Correct answer)

Correct answer: The point on the ground directly below the camera's perspective center (ground nadir), or its image (photo nadir)

Nadir refers to the ground point directly below the camera's perspective center (ground nadir) and its corresponding image location (photo nadir), which lies at the geometric center of a perfectly vertical photograph.

Question 4: Which type of point cloud classification separates ground returns from vegetation and structures?

Principal component analysis
Radiometric classification
LAS class 2 (ground) filtering using algorithms like Progressive TIN or CSF (Correct answer)
K-means spectral clustering

Correct answer: LAS class 2 (ground) filtering using algorithms like Progressive TIN or CSF

Ground classification assigns LAS class 2 to bare-earth returns using algorithms like Progressive Triangulated Irregular Network (PTIN) or Cloth Simulation Filter (CSF) that distinguish ground from above-ground features.

Question 5: In AT processing, what is a 'pass point'?

A control point verified by the client
A point measured in consecutive photos along a flight strip to pass geometry forward (Correct answer)
A point where two flight lines cross
The nadir point directly below the aircraft

Correct answer: A point measured in consecutive photos along a flight strip to pass geometry forward

A pass point is measured in consecutive overlapping photographs along a strip to propagate (pass) the geometry from one model to the next.

Question 6: What is a 'production specification' (project specification) in photogrammetric mapping?

A software configuration file for the photogrammetric workstation
The technical and contractual document defining all requirements for data acquisition, processing, accuracy, deliverables, and formats for a specific mapping project (Correct answer)
A specification sheet for the aerial camera model used in production
The flight plan parameters determined by the acquisition contractor

Correct answer: The technical and contractual document defining all requirements for data acquisition, processing, accuracy, deliverables, and formats for a specific mapping project

A production specification is the comprehensive technical document—typically developed with or for the client—that defines all requirements including accuracy standards, feature content, formats, delivery schedule, and QC procedures for the project.

Question 7: Which type of satellite sensor detects reflected sunlight?

Magnetic resonance scanner
Active radar sensor
Passive sensor (Correct answer)
Ground-penetrating sonar

Correct answer: Passive sensor

Passive sensors detect and measure natural radiation that is reflected or emitted from the Earth's surface, such as sunlight or thermal energy. They do not generate their own energy source, relying instead on ambient energy, making them dependent on external illumination like the sun. Examples include traditional cameras and many satellite imagers.

Question 8: What is the main purpose of photogrammetric data acquisition?

Artistic photography
Data encryption
Mapping and measurement (Correct answer)
Video editing

Correct answer: Mapping and measurement

The main purpose of photogrammetric data acquisition is to obtain precise measurements and create accurate maps or 3D models of objects and terrain. By using photographs, photogrammetry allows for the extraction of geometric information, which is crucial for applications in surveying, engineering, and geographic information systems (GIS).

Question 9: What does 'lineage' mean as a dimension of geospatial data quality?

A description of the history of the data—including source materials, collection methods, processing steps, and transformations applied (Correct answer)
The archival storage location and retention policy for the data
The accuracy inheritance from parent to child datasets in a pyramid tile scheme
The family tree of the software developers who created the GIS platform

Correct answer: A description of the history of the data—including source materials, collection methods, processing steps, and transformations applied

Lineage documents the origin and history of the data—what source materials were used, how they were collected, what processing and transformations were applied—enabling users to assess fitness for purpose and reproduce results.

Question 10: What is 'voxel-based' point cloud processing?

Converting point clouds to 2D raster images for visualization
Applying color correction using HSV color model
Merging point clouds from multiple flight dates
Processing point clouds in a 3D grid of volumetric cells (voxels) for efficient spatial analysis (Correct answer)

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

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 11: What is the overlap percentage typically required between consecutive aerial photos?

40%
60% (Correct answer)
20%
80%

Correct answer: 60%

A 60% overlap (forward lap) between consecutive aerial photos is a standard requirement in photogrammetry. This significant overlap ensures that every point on the ground is visible in at least two, and often three, images, which is crucial for creating stereoscopic models. This redundancy allows for accurate aerotriangulation, the generation of precise digital elevation models (DEMs), and the production of seamless orthophotos without gaps.

Question 12: What is the term for the area captured in a single aerial photograph?

Frame buffer
Viewport
Pixel zone
Ground coverage (Correct answer)

Correct answer: Ground coverage

Ground coverage refers to the actual area on the Earth's surface that is captured within a single aerial photograph. This area is determined by factors such as the camera's focal length, the sensor size, and the flight altitude. Understanding ground coverage is essential for planning flight paths and ensuring complete area mapping.

Question 13: What is the 'y-parallax' in a stereopair, and what does excessive y-parallax indicate?

The parallax introduced by atmospheric refraction
The vertical image displacement caused by relief; it indicates high terrain
The horizontal parallax difference used to measure elevation
Residual vertical displacement after relative orientation; it indicates incomplete relative orientation (Correct answer)

Correct 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.

Question 14: What is a 'mosaic dodging' or 'color balancing' algorithm used for in orthomosaic production?

Detecting and removing cloud shadows from imagery
Adjusting the brightness and color of individual photos to achieve a visually seamless mosaic (Correct answer)
Resampling all orthophotos to a common ground pixel size
Removing GPS positional errors from individual orthophotos

Correct answer: Adjusting the brightness and color of individual photos to achieve a visually seamless mosaic

Dodging and color balancing algorithms adjust brightness, contrast, and color of individual source orthophotos so that the final mosaic has a uniform appearance without visible lighting differences.

Question 15: Which laboratory calibration method uses precision optical collimators to simulate distant targets at infinity?

Stellar calibration
Goniometer calibration (Correct answer)
On-the-job self-calibration
Test field calibration

Correct answer: Goniometer calibration

Goniometer calibration uses a precision instrument with collimators to project parallel rays simulating targets at infinity, enabling measurement of angular relationships and lens distortion in a controlled lab environment.

Question 16: In photogrammetric production, what is a 'calibration certificate' for a metric camera?

A laboratory report documenting the camera's interior orientation parameters (principal distance, principal point, lens distortion) determined by calibration (Correct answer)
A flight plan approval document from aviation authorities
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 17: What is the 'base-to-height ratio' (B/H ratio) in aerial stereophotogrammetry?

The ratio of image scale to map scale
The ratio of flying height to camera focal length
The ratio of the air base (distance between exposure stations) to the flying height, affecting depth measurement sensitivity (Correct answer)
The ratio of forward overlap to sidelap percentage

Correct 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.

Question 18: What is the 'sigma naught' (σ₀) in bundle adjustment output?

The standard deviation of unit weight, indicating overall solution quality (Correct answer)
The number of iterations to convergence
The nadir angle of the camera
The RMS flight altitude deviation

Correct answer: The standard deviation of unit weight, indicating overall solution quality

Sigma naught (σ₀) is the standard deviation of unit weight from the least-squares solution, providing an overall indicator of the internal consistency and quality of the adjustment.

Question 19: What is 'mass point collection' in stereo compilation?

The collection of coordinate data from heavy-density urban areas only
The systematic collection of random elevation measurements across the terrain to support TIN and DEM generation (Correct answer)
Counting the number of control points in the block
Measuring the mass of collected field samples

Correct answer: The systematic collection of random elevation measurements across the terrain to support TIN and DEM generation

Mass point collection involves systematically measuring a large number of random elevation points across the terrain, providing the raw data needed to build an accurate TIN or DEM surface model.

Question 20: What does the term 'block of photographs' refer to in aerial triangulation?

A single stereopair used for mapping
A collection of overlapping photographs covering an entire project area (Correct answer)
The physical film magazine in the camera
A set of control points in a rectangular arrangement

Correct answer: A collection of overlapping photographs covering an entire project area

A block of photographs is the entire collection of overlapping images that covers a mapping project area, processed together in a single triangulation solution.

Question 21: A camera with a 150 mm focal length is flown at 3,000 m above ground level. What is the approximate nominal image scale?

1:2,000
1:200,000
1:200
1:20,000 (Correct answer)

Correct answer: 1:20,000

Image scale = f/H = 0.150 m / 3,000 m = 1/20,000, giving a scale of 1:20,000.

Question 22: What is the function of a geodetic datum?

It generates topographic symbols
It tracks earthquakes
It defines positional references and coordinate systems (Correct answer)
It processes image enhancement

Correct answer: It defines positional references and coordinate systems

A geodetic datum is a fundamental reference system that defines the size and shape of the Earth (using a specific ellipsoid) and the origin and orientation of a coordinate system. It provides the framework for accurately measuring and expressing geographic coordinates (latitude, longitude, and height). Datums ensure consistency and precision across all mapping, surveying, and geospatial data applications.

Question 23: What is remote sensing primarily used for in photogrammetry?

Installing weather equipment
Collecting soil samples
Measuring tree height manually
Capturing spatial information from a distance (Correct answer)

Correct answer: Capturing spatial information from a distance

Remote sensing is the process of acquiring information about an object or phenomenon without making physical contact with it, typically using sensors on aircraft or satellites. In photogrammetry, it specifically involves capturing aerial or satellite images to derive spatial data, such as measurements, maps, and 3D models. It allows for broad-scale data collection from a distance.

Question 24: Which model represents the Earth's surface for mapping and surveying?

Gravity model
Polygon mesh
Atmosphere layer
Ellipsoid (Correct answer)

Correct answer: Ellipsoid

The ellipsoid is a mathematical model that approximates the Earth's shape as an oblate spheroid, which is slightly flattened at the poles and bulging at the equator. This smooth, mathematically defined surface provides a precise reference for geodetic calculations, allowing for accurate measurements of latitude, longitude, and elevation. It serves as the fundamental geometric basis for mapping and surveying.

Question 25: What are the three rotation angles used to describe camera orientation in standard photogrammetric convention?

Alpha, beta, gamma
Omega, phi, kappa (Correct answer)
Azimuth, elevation, bank
Roll, pitch, yaw

Correct answer: Omega, phi, kappa

In photogrammetry, the three rotation angles omega (ω), phi (φ), and kappa (κ) define the rotational orientation of the camera relative to the ground coordinate system.

Question 26: Which factor most influences the scale of an aerial photograph?

Camera weight
Image compression
Film type
Flight altitude (Correct answer)

Correct answer: Flight altitude

The flight altitude is the most significant factor influencing the scale of an aerial photograph. A higher flight altitude results in a smaller scale photograph, meaning a larger ground area is covered but with less detail. Conversely, a lower flight altitude produces a larger scale photograph, showing more detail over a smaller ground area.

Question 27: What is spatial analysis primarily used for?

Examining spatial patterns and relationships (Correct answer)
Measuring file sizes
Recording weather patterns
Adjusting color contrast in images

Correct answer: Examining spatial patterns and relationships

Spatial analysis is a set of techniques used to analyze data that has a geographic or spatial component. Its primary purpose is to uncover patterns, trends, and relationships that are not evident in non-spatial data, helping to understand phenomena across space. This involves using location, distance, and connectivity to derive meaningful insights.

Question 28: What is 'multi-ray' matching in photogrammetric dense reconstruction?

A technique for matching features across different spectral bands
Matching image features using only two overlapping images (stereopair)
Simultaneously using three or more overlapping images to improve matching reliability and accuracy (Correct answer)
A method for connecting flight strips using cross-tie points

Correct answer: Simultaneously using three or more overlapping images to improve matching reliability and accuracy

Multi-ray matching uses three or more overlapping images simultaneously to verify and improve the reliability of matched points, reducing errors compared to stereopair-only matching.

Question 29: What are the six elements of exterior orientation for a single photograph?

X, Y, Z (position of perspective center) and ω, φ, κ (three rotation angles) (Correct answer)
Focal length, principal point x, principal point y, radial distortion k1, k2, k3
Scale, rotation, translation (2D), and focal length
Latitude, longitude, altitude, roll, pitch, yaw (as GPS/IMU output only)

Correct 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.

Question 30: What is 'noise filtering' in point cloud processing?

Removing duplicate image exposures from the project
Filtering GPS positions with poor PDOP
Removing radiometric speckle from raster images
Eliminating outlier points that do not represent actual surfaces (e.g., flying points) (Correct answer)

Correct answer: Eliminating outlier points that do not represent actual surfaces (e.g., flying points)

Noise filtering removes outlier or erroneous points—such as isolated flying points far from the main surface—that would degrade the accuracy of derived terrain models.

Question 31: What role does the 'datum' play in aerial triangulation?

It defines the coordinate system to which the solution is referenced (Correct answer)
It determines the camera calibration report format
It specifies the required image overlap percentage
It sets the minimum number of photos in a block

Correct answer: It defines the coordinate system to which the solution is referenced

The datum defines the coordinate reference system (e.g., NAD83, WGS84) to which the triangulated block is tied through the ground control points.

Question 32: In digital aerial cameras, what component replaces the photographic film at the focal plane?

The lens system
The shutter mechanism
The CCD or CMOS image sensor (Correct answer)
The viewfinder assembly

Correct answer: The CCD or CMOS image sensor

In digital cameras, the CCD or CMOS sensor array is positioned at the focal plane to capture light, directly replacing the role of photographic film as the image recording medium.

Question 33: What is the purpose of 'edge matching' in stereo compilation projects?

Aligning GPS trajectories from two different flight days
Ensuring that map features compiled in adjacent stereomodels connect seamlessly at model boundaries (Correct answer)
Connecting control points across different coordinate zones
Matching the color histogram of adjacent photographs

Correct answer: Ensuring that map features compiled in adjacent stereomodels connect seamlessly at model boundaries

Edge matching ensures that map features (roads, contours, building outlines) compiled in adjacent stereomodels align perfectly at the boundaries between models, maintaining topological continuity.

Question 34: Which camera calibration parameter corrects for non-orthogonality (shear) between the x and y axes of the image coordinate system?

Focal length correction
Affinity (shear) parameter (Correct answer)
Radial distortion coefficient K1
Principal point offset

Correct answer: Affinity (shear) parameter

The affinity or shear parameter corrects for non-orthogonality between the image coordinate axes, which can result from imperfect sensor geometry or digitizer scanning.

Question 35: Which type of camera is commonly used in aerial photogrammetry?

Metric camera (Correct answer)
Handheld DSLR
Phone camera
Film projector

Correct answer: Metric camera

A metric camera is specifically designed for photogrammetric applications due to its high geometric stability and precisely calibrated internal parameters. Unlike consumer cameras, metric cameras minimize lens distortions and provide accurate focal length and principal point information, which are essential for precise measurements and mapping. This ensures the geometric integrity required for photogrammetric processing.

Question 36: What is a TIN (Triangulated Irregular Network) in 3D modeling?

A network of GPS base stations for differential correction
A point cloud storage format for LiDAR data
A raster grid interpolated from contour lines
A surface model composed of irregular triangular facets connecting measured mass points and breaklines (Correct answer)

Correct answer: A surface model composed of irregular triangular facets connecting measured mass points and breaklines

A TIN is a vector-based surface model made of irregular triangular facets connecting measured points and breaklines, faithfully representing terrain morphology including sharp features like ridges.

Question 37: What is the purpose of 'thinning' or 'decimating' a point cloud?

Reducing point cloud size by removing redundant points while preserving surface representation (Correct answer)
Splitting a large point cloud into manageable tiles
Increasing point density through interpolation
Adding color attributes to uncolored points

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

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 38: What does 'positional accuracy' mean in the ASPRS/FGDC standards context?

The alignment between GPS-collected and photogrammetrically derived features
The qualitative description of a dataset's fitness for a specific use
The pixel-level sharpness of the orthophoto product
The closeness of the reported positions of features to their true positions on the Earth's surface (Correct answer)

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 39: What is a key advantage of active remote sensing systems like LiDAR?

They function in any lighting conditions (Correct answer)
They depend on visible light reflection
They only measure air temperature
They require daylight to operate

Correct answer: They function in any lighting conditions

A key advantage of active remote sensing systems, such as LiDAR or radar, is their ability to emit their own energy (e.g., laser pulses or microwaves) and measure the reflected signal. This independence from external light sources allows them to collect data effectively during both day and night, and often through atmospheric conditions like clouds or haze, ensuring consistent data acquisition.

Question 40: What is a 'digital terrain model' (DTM) compared to a 'digital elevation model' (DEM)?

DTM and DEM are interchangeable terms with identical definitions
DTM includes breaklines and mass points (vector + raster hybrid) representing the bare-earth terrain; DEM is often used as a generic term for any elevation raster (Correct answer)
DTM always has higher resolution than DEM
DEM represents only sea-floor bathymetry, while DTM represents land elevation

Correct answer: DTM includes breaklines and mass points (vector + raster hybrid) representing the bare-earth terrain; DEM is often used as a generic term for any elevation raster

A DTM includes both the raster elevation grid and vector elements (breaklines, mass points) representing bare-earth terrain features; DEM is often used generically for any elevation raster, including DSMs.

Question 41: What is the principal point in camera calibration?

The point where the optical axis intersects the image plane (Correct answer)
The midpoint between two fiducial marks
The geometric center of the image frame
The projection center of the lens

Correct answer: The point where the optical axis intersects the image plane

The principal point is where the optical axis intersects the image plane, representing the foot of the perpendicular from the perspective center to the image plane.

Question 42: Which type of map projection preserves area but distorts shape?

Perspective projection
Orthophoto projection
Conformal projection
Equal-area projection (Correct answer)

Correct answer: Equal-area projection

An equal-area (or equivalent) projection is specifically designed to preserve the relative sizes of geographic features on the map. This means that the area of any region on the map is proportional to its actual area on the Earth. However, to maintain area accuracy, these projections typically distort the shapes of features, especially towards the edges of the map.

Question 43: What is a 'floating mark' in analogue or softcopy stereo compilation?

A stereoscopic measuring mark that appears to float at a selected elevation within the stereomodel (Correct answer)
An unregistered control point that is not tied to the datum
A GPS receiver that drifts during flight
A tie point that only appears in one photograph

Correct 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.

Question 44: In UAV/drone photogrammetry, what overlap configuration is typically recommended for high-quality 3D reconstruction?

80–90% forward overlap and 70–80% sidelap (Correct answer)
60% forward overlap and 30% sidelap
50% forward overlap and 50% sidelap
95% forward overlap and 20% sidelap

Correct answer: 80–90% forward overlap and 70–80% sidelap

High-quality UAV 3D reconstruction typically requires 80–90% forward overlap and 70–80% sidelap to ensure every surface area is seen from multiple angles for robust matching.

Question 45: What does 'logical consistency' mean in geospatial data quality standards (ISO 19157)?

The agreement between the dataset and ground truth check points
The matching of feature attributes between different data sources
The consistency of radiometric values across the image mosaic
The degree to which a dataset conforms to its data model rules, including topological correctness and no invalid geometries (Correct answer)

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 46: Which term describes the interpretation of remotely sensed images to classify land cover?

Pixel smoothing
Raster compositing
Histogram equalization
Image classification (Correct answer)

Correct answer: Image classification

Image classification is the process of categorizing pixels in a remotely sensed image into different land cover or land use classes (e.g., forest, water, urban, agriculture). This is achieved by analyzing the spectral characteristics of pixels and assigning them to predefined categories, creating thematic maps that represent the distribution of various features on the Earth's surface.

Question 47: Which distortion model parameter primarily describes symmetric radial lens distortion?

K1 radial distortion coefficient (Correct answer)
Affinity coefficient
Principal point offset
Decentering coefficient P1

Correct answer: K1 radial distortion coefficient

K1 is the primary radial distortion coefficient that describes symmetric, rotationally symmetric distortion measured from the lens center outward.

Question 48: What does 'resampling' mean in the context of raster photogrammetric products?

Re-flying an area to collect additional imagery
Resampling GPS trajectories to a uniform time interval
Collecting additional ground control points after initial triangulation
The process of computing pixel values at new grid positions during geometric transformations (e.g., bilinear, cubic convolution) (Correct answer)

Correct answer: The process of computing pixel values at new grid positions during geometric transformations (e.g., bilinear, cubic convolution)

Resampling computes new pixel values during raster transformation using interpolation methods—nearest neighbor preserves sharp edges, bilinear smooths slightly, and cubic convolution provides the best quality at higher cost.

Question 49: What is 'data completeness' as a dimension of geospatial data quality?

The percentage of image pixels with valid radiometric values
The number of check points used to assess accuracy
The ratio of collected mass points to the project area
The degree to which all required features and attributes are present and correctly represented in the dataset (Correct answer)

Correct answer: The degree to which all required features and attributes are present and correctly represented in the dataset

Data completeness measures whether all required features, objects, and attributes are present in the dataset without omissions or commissions, as specified by the product standard or project specification.

Question 50: In stereo compilation, what is the function of the 'model coordinate system'?

An arbitrary local 3D coordinate system defined by the relative orientation of a stereopair, before absolute orientation is applied (Correct answer)
The pixel coordinate system of the scanned image
The final geographic coordinate system of the mapping project
The coordinate system of the IMU unit on the aircraft

Correct answer: An arbitrary local 3D coordinate system defined by the relative orientation of a stereopair, before absolute orientation is applied

The model coordinate system is the arbitrary local 3D system defined after relative orientation of a stereopair, in which measurements can be made before the model is transformed to real-world coordinates through absolute orientation.

Question 51: What is 'differential rectification' in orthophoto production?

Removing systematic sensor distortions using a flat-field calibration
Adjusting color differences between overlapping photographs
Correcting images pixel-by-pixel using a DEM to remove relief displacement across the entire image (Correct answer)
Correcting GPS positions using a reference base station

Correct answer: Correcting images pixel-by-pixel using a DEM to remove relief displacement across the entire image

Differential rectification corrects each pixel individually using a DEM, removing the varying relief displacement across the image to produce a geometrically accurate orthophoto.

Question 52: Strip deformation in aerial triangulation typically appears as what type of systematic error?

Random noise on individual image measurements
Uniform scale error across the entire block
Rotation of the entire block around the Z-axis
A 'bow' or 'banana' shape bending along the flight strip (Correct answer)

Correct answer: A 'bow' or 'banana' shape bending along the flight strip

Strip deformation manifests as a systematic bow or banana-shaped bending along a flight strip, caused by accumulated errors in relative orientation between successive stereomodels.

Question 53: Self-calibrating bundle adjustment simultaneously solves for which additional unknowns?

Image scan resolution
Camera interior orientation parameters (additional parameters) (Correct answer)
Ground control point coordinates
Aircraft velocity and heading

Correct answer: Camera interior orientation parameters (additional parameters)

Self-calibrating bundle adjustment adds camera interior orientation parameters—such as principal point offset, radial distortion, and decentering distortion—as additional unknowns in the solution.

Question 54: What does interior orientation define in photogrammetry?

The position and attitude of the camera in the world coordinate system
The geometric relationship between the image plane and the perspective center (Correct answer)
The transformation from pixel to ground coordinates
The spatial relationship between overlapping images

Correct answer: The geometric relationship between the image plane and the perspective center

Interior orientation defines the geometric relationship between the image coordinate system and the perspective center, including focal length, principal point location, and lens distortion parameters.

Question 55: What is the collinearity condition in photogrammetry?

Parallel flight lines must be equidistant
All tie points must be visible in at least three photos
Three ground control points must form a right triangle
The object point, perspective center, and image point all lie on a straight line (Correct answer)

Correct answer: The object point, perspective center, and image point all lie on a straight line

The collinearity condition states that the object point, the camera's perspective center, and the corresponding image point are collinear—forming the mathematical basis for photogrammetric equations.

Question 56: Which type of aerial camera lens has an angular field of view greater than 100 degrees and is used for small-scale mapping?

Normal-angle lens (about 60°)
Superwide-angle lens (about 120°) (Correct answer)
Telephoto lens (about 30°)
Wide-angle lens (about 90°)

Correct answer: Superwide-angle lens (about 120°)

Superwide-angle lenses have angular fields of view greater than 100 degrees (typically ~120°), covering large ground areas per photograph, making them suited for small-scale topographic mapping.

Question 57: Which atmospheric condition negatively impacts aerial photogrammetry quality?

No wind
Low humidity
Heavy cloud cover (Correct answer)
Clear skies

Correct answer: Heavy cloud cover

Heavy cloud cover severely obstructs the ground surface from the aerial camera's view. This prevents the acquisition of clear, complete, and usable imagery, leading to significant gaps in data and poor image quality. Without visible ground features, accurate photogrammetric processing, such as stereoscopic matching and 3D model generation, becomes impossible or highly unreliable.

Question 58: What is the calibrated focal length (CFL) in photogrammetry?

The focal length measured when focused at infinity
The distance from the rear nodal point to the film plane
The manufacturer's nominal specified focal length
The focal length value that minimizes the overall effect of radial distortion across the image (Correct answer)

Correct answer: The focal length value that minimizes the overall effect of radial distortion across the image

The calibrated focal length is the value that minimizes the overall effect of radial lens distortion across the image format, and may differ slightly from the manufacturer's specification.

Question 59: In a LiDAR or photogrammetric point cloud, what does 'point density' measure?

The color saturation of each point
The compression ratio of the LAS file
The number of points per unit area (e.g., points per square meter) (Correct answer)
The vertical accuracy of individual points

Correct answer: The number of points per unit area (e.g., points per square meter)

Point density is the number of points per unit area (typically points/m²), which determines the level of surface detail and the accuracy of derived products like DEMs.

Question 60: What is the primary purpose of land surveying?

Tracking cloud cover
Measuring rainfall
Counting wildlife populations
Measuring and mapping land positions and boundaries (Correct answer)

Correct answer: Measuring and mapping land positions and boundaries

The primary purpose of land surveying is to accurately determine and map the terrestrial or three-dimensional position of points, and the distances and angles between them. This is essential for establishing and defining property boundaries, planning and designing infrastructure, and creating precise maps for legal, engineering, and construction purposes.

Question 61: What is 'image rectification' in the photogrammetric workflow?

Transforming an image to remove tilt distortion so it appears as if taken from directly above (nadir) (Correct answer)
Correcting camera interior orientation parameters in the field
Adding color balance between adjacent flight strips
Reprocessing failed GPS trajectories after landing

Correct answer: Transforming an image to remove tilt distortion so it appears as if taken from directly above (nadir)

Image rectification transforms a tilted aerial photograph to remove tilt effects, producing an image that appears as if taken from directly above—a prerequisite for creating orthophotos.

Question 62: In digital orthophoto production, what causes 'smear' artifacts in urban areas?

Excessive JPEG compression during orthophoto tile generation
Atmospheric haze reducing image contrast in urban areas
The use of a DTM (bare-earth) instead of a DSM (full surface) for rectification, causing building rooftops to smear across adjacent areas (Correct answer)
GPS positioning errors causing misalignment of adjacent photos

Correct answer: The use of a DTM (bare-earth) instead of a DSM (full surface) for rectification, causing building rooftops to smear across adjacent areas

Smear artifacts in urban orthophotos occur when a bare-earth DTM is used for rectification, causing building rooftops—which are elevated above ground—to be incorrectly projected and smeared across adjacent areas.

Question 63: What is a 'flight report' in aerial photogrammetry production?

A summary of the project's financial expenditures
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 legal document filed with the FAA after each flight

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 64: What is 'relief displacement' in aerial photography?

The difference in elevation between two adjacent stereomodels
The shift of elevated objects outward from the nadir point on a vertical photograph (Correct answer)
The error caused by aircraft crabbing (heading vs. track)
The displacement of the horizon line in oblique photography

Correct answer: The shift of elevated objects outward from the nadir point on a vertical photograph

Relief displacement is the radial outward shift of elevated objects from the nadir point on a vertical aerial photograph, caused by the perspective projection of terrain relief.

Question 65: What causes decentering (tangential) lens distortion?

Misalignment of optical elements from the optical axis within the lens system (Correct answer)
Curvature mismatch of the lens elements
Atmospheric refraction of light rays
Temperature variations during flight operations

Correct answer: Misalignment of optical elements from the optical axis within the lens system

Decentering distortion is caused by the physical misalignment or decentering of lens elements from the optical axis, producing an asymmetric distortion pattern.

Question 66: Which type of ground control point provides both horizontal position and elevation?

Vertical-only control
Photo-identifiable point
Full control (3D) (Correct answer)
Horizontal-only control

Correct answer: Full control (3D)

Full control points (3D) provide X, Y, and Z coordinates, fully constraining the photogrammetric network in all three dimensions.

Question 67: What is 'breakline' collection in stereo compilation?

Collecting linear features (ridgelines, drainage lines, roads edges) that define sharp changes in terrain slope for accurate TIN and DEM generation (Correct answer)
Recording the borders between photo strips
Identifying areas of layover in urban imagery
Detecting image matching failures along edges

Correct answer: Collecting linear features (ridgelines, drainage lines, roads edges) that define sharp changes in terrain slope for accurate TIN and DEM generation

Breaklines are collected along ridges, streams, road edges, and other features representing abrupt slope changes, ensuring that TINs and DEMs accurately model terrain discontinuities.

Question 68: What is the difference between a DSM and a DTM?

DSM (Digital Surface Model) includes all features above ground; DTM (Digital Terrain Model) represents only bare earth (Correct answer)
DSM uses LiDAR data while DTM uses photogrammetric data
DSM has higher resolution than DTM by definition
DSM is in vector format and DTM is in raster format

Correct answer: DSM (Digital Surface Model) includes all features above ground; DTM (Digital Terrain Model) represents only bare earth

A DSM (Digital Surface Model) represents the top of all surfaces including buildings and vegetation, while a DTM (Digital Terrain Model) represents only the bare-earth terrain after removing above-ground features.

Question 69: In aerial photography, fiducial marks are used primarily to:

Determine the aircraft flight altitude
Calibrate the onboard GPS receiver
Define the image coordinate system (Correct answer)
Measure ground control points

Correct answer: Define the image coordinate system

Fiducial marks are reference points etched into the camera's focal plane that define the image coordinate system and allow transformation from scanner to image coordinates.

Question 70: What does exterior orientation of a photograph define?

The calibration parameters of the lens distortion
The image coordinate system origin
The internal geometric parameters of the camera
The position and rotational attitude of the camera at the moment of exposure (Correct answer)

Correct answer: The position and rotational attitude of the camera at the moment of exposure

Exterior orientation defines the six parameters — X, Y, Z position and omega, phi, kappa rotation angles — describing where the camera was and how it was oriented when the photo was taken.

Question 71: What is the purpose of a reseau grid (reseau plate) in analog aerial cameras?

To improve image sharpness at the corners of the frame
To filter ultraviolet radiation from sunlight
To record the exact time of each exposure
To provide reference marks for detecting and correcting film deformation (Correct answer)

Correct answer: To provide reference marks for detecting and correcting film deformation

A reseau grid contains precisely positioned crosses or dots imaged onto the film, allowing detection and correction of film deformation that may occur during processing or scanning.

Question 72: What is 'ground sample distance' (GSD) in digital photogrammetry?

The spacing between flight lines
The minimum detectable elevation difference
The real-world size represented by one pixel in the image (Correct answer)
The distance between GPS ground control points

Correct answer: The real-world size represented by one pixel in the image

GSD (Ground Sample Distance) is the real-world dimension represented by a single pixel in the image, determining the spatial resolution of the final mapping products.

Question 73: Which technique measures elevation differences between points?

Radial plotting
Azimuth calculation
Histogram matching
Leveling (Correct answer)

Correct answer: Leveling

Leveling is a fundamental surveying technique specifically designed to measure differences in elevation or height between points on the Earth's surface. It uses an instrument called a level and a graduated staff to determine relative heights accurately. This method is crucial for construction, mapping, and engineering projects where precise vertical control is required.

Question 74: The f-number (f/stop) of a photogrammetric camera lens is defined as:

The effective aperture diameter divided by the focal length
The focal length divided by the effective aperture (entrance pupil) diameter (Correct answer)
The ratio of image distance to object distance
The number of optical elements in the lens system

Correct answer: The focal length divided by the effective aperture (entrance pupil) diameter

The f-number is the ratio of the focal length to the effective aperture (entrance pupil) diameter, controlling the amount of light reaching the film or sensor plane.

Question 75: In digital photogrammetry, what is 'epipolar geometry' used for?

Constraining image matching to a 1D search along epipolar lines, reducing computation and false matches (Correct answer)
Correcting color balance between adjacent strips
Converting pixel coordinates to geographic coordinates
Defining the flight line spacing for a project

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

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 76: According to ASPRS accuracy standards, what should be done when accuracy test results exceed the stated accuracy class threshold?

The data should be immediately deleted and re-acquired
The project manager should be notified but no reclassification is required
The accuracy threshold should be recalculated using a larger confidence interval
The data should be reported as meeting the next lower accuracy class, not the originally specified class (Correct answer)

Correct answer: The data should be reported as meeting the next lower accuracy class, not the originally specified class

When RMSE results exceed the threshold for the specified accuracy class, the data must be reported as meeting only the lower accuracy class that its actual RMSE does satisfy, ensuring honest representation of the product's quality.

Question 77: In bundle adjustment, what is minimized during the least-squares solution?

The overlap percentage between adjacent photos
The number of ground control points
The flying height above terrain
The sum of squared residuals of image coordinate measurements (Correct answer)

Correct answer: The sum of squared residuals of image coordinate measurements

Bundle adjustment minimizes the sum of squared residuals of image coordinate measurements, simultaneously solving for camera positions, orientations, and object point coordinates.

Question 78: Which projection is commonly used for world maps and navigation charts?

Mercator projection (Correct answer)
Gnomonic projection
Orthographic projection
Albers equal-area

Correct answer: Mercator projection

The Mercator projection is widely used for world maps and navigation charts due to its unique properties. It preserves angles and shapes (conformal) and represents lines of constant bearing (rhumb lines) as straight lines, which is invaluable for marine and aeronautical navigation. While it severely distorts areas, particularly at higher latitudes, its angular preservation makes it ideal for directional accuracy.

Question 79: Which type of remote sensing uses emitted microwave energy to collect data?

Active radar sensors (Correct answer)
Thermal sensors
Magnetometers
Photographic cameras

Correct answer: Active radar sensors

Active radar sensors, such as Synthetic Aperture Radar (SAR), emit their own microwave energy pulses and then measure the reflected signal. This allows them to collect data independently of natural illumination and through atmospheric conditions like clouds or smoke. This capability makes them valuable for all-weather, day-and-night remote sensing applications.

Question 80: What is the role of a flight plan in aerial photogrammetry?

To monitor film development
To adjust image contrast
To document ground measurements
To define image coverage paths and overlaps (Correct answer)

Correct answer: To define image coverage paths and overlaps

A flight plan is a meticulously designed route that dictates the aircraft's path, altitude, and camera firing intervals over a project area. Its primary role is to ensure systematic and complete photographic coverage, defining the precise image locations and the required forward and side overlaps between images. This planning is critical for efficient data acquisition and successful subsequent photogrammetric processing.

Question 81: What accuracy class does ASPRS 2014 assign when RMSEz of a DEM equals 10 cm?

The DEM meets Class 1 specifications for 1 m GSD products
The DEM is classified as a bare-earth DTM regardless of source GSD
The DEM meets accuracy for products with 10 cm Non-Vegetated Vertical Accuracy (NVA) (Correct answer)
The DEM meets Class 2 specifications for 5 cm GSD products

Correct answer: The DEM meets accuracy for products with 10 cm Non-Vegetated Vertical Accuracy (NVA)

Under ASPRS 2014, a DEM with RMSEz = 10 cm has a Non-Vegetated Vertical Accuracy (NVA) of approximately 19.6 cm (95% confidence), placing it in the accuracy class for products with 10 cm NVA.

Question 82: The Modulation Transfer Function (MTF) in optical and sensor systems is used to measure:

The sensor dark current noise level
The accuracy of onboard GPS position measurements
The radial lens distortion profile
The ability of the system to resolve and transfer spatial frequency detail (Correct answer)

Correct answer: The ability of the system to resolve and transfer spatial frequency detail

MTF quantifies how well an optical system transfers contrast from the scene to the image at different spatial frequencies, characterizing the overall resolving power and sharpness of the system.

Question 83: In digital photogrammetry, pixel size of the sensor is most directly related to:

The shutter speed setting
The ground sample distance (GSD) (Correct answer)
The lens radial distortion magnitude
The focal length of the camera lens

Correct answer: The ground sample distance (GSD)

Pixel size directly determines the ground sample distance (GSD) for a given flying height and focal length; GSD defines the smallest ground detail that can be resolved.

Question 84: What is 'stereo compilation QC' (quality control) typically checking for?

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 color calibration of the stereo display monitor

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 85: What is 'vegetated vertical accuracy' (VVA) and why is it reported separately from NVA?

VVA is the accuracy of vegetation height measurements; it differs because vegetation returns are more accurate than ground returns
VVA applies only to forestry mapping projects and is not required for standard ASPRS accuracy reporting
VVA uses the 68% confidence level while NVA uses the 95% level
VVA is the 95th percentile absolute error in vegetated areas; it is reported separately because vegetation obscures the ground, causing higher and more variable errors (Correct answer)

Correct answer: VVA is the 95th percentile absolute error in vegetated areas; it is reported separately because vegetation obscures the ground, causing higher and more variable errors

VVA is the 95th percentile absolute error in vegetated areas; it is reported separately because vegetation canopy obscures the ground surface, causing higher and less predictable errors than in open areas.

Question 86: What is 'occlusion' in the context of dense image matching?

Areas not visible in one or more images due to blocking by objects (Correct answer)
GPS signal dropout during acquisition
Radiometric saturation in bright areas
Lens vignetting at image edges

Correct answer: Areas not visible in one or more images due to blocking by objects

Occlusion occurs when objects (buildings, trees) block the line of sight to certain areas in some images, creating gaps or reduced accuracy in the resulting point cloud.

Question 87: What is chromatic aberration in photogrammetric camera lenses?

The failure of a lens to focus different wavelengths of light at the same focal point (Correct answer)
Motion blurring caused by aircraft vibration during exposure
Distortion caused by temperature-induced changes in the lens
Vignetting (light falloff) at the edges of the image frame

Correct answer: The failure of a lens to focus different wavelengths of light at the same focal point

Chromatic aberration occurs when a lens fails to focus all wavelengths of light at exactly the same focal point, causing color fringing or reduced sharpness, particularly visible at high-contrast edges.

Question 88: What is 'hypsographic tinting' in topographic map design?

The representation of water bodies using blue tints
The process of digitizing contour lines from stereo imagery
A color correction technique for multispectral imagery
The use of graduated colors to represent elevation zones, typically from green (lowlands) to brown/white (highlands) (Correct answer)

Correct answer: The use of graduated colors to represent elevation zones, typically from green (lowlands) to brown/white (highlands)

Hypsographic tinting uses a graduated color scheme keyed to elevation, traditionally ranging from green at low elevations through yellow, orange, brown, and white at high elevations to visually communicate terrain relief.

Question 89: What algorithm is most commonly used for automatic image matching to generate dense point clouds?

Inverse distance weighting
RANSAC feature rejection only
Semi-Global Matching (SGM) or Multi-View Stereo (MVS) (Correct answer)
Kriging interpolation

Correct answer: Semi-Global Matching (SGM) or Multi-View Stereo (MVS)

Semi-Global Matching (SGM) and Multi-View Stereo (MVS) are the dominant algorithms for dense image matching that produce high-density point clouds from overlapping photographs.

Question 90: Which projection is best suited for mapping polar regions?

Sinusoidal projection
Azimuthal projection (Correct answer)
Mercator projection
Polyconic projection

Correct answer: Azimuthal projection

Azimuthal (or planar) projections are best suited for mapping polar regions because they project the Earth onto a flat plane tangent to one of the poles. This configuration minimizes distortion around the central point (the pole) and accurately represents directions from that point. This makes them ideal for navigation and mapping in high-latitude areas where other projections introduce extreme distortions.

Question 91: The collinearity condition in photogrammetry states that:

Control points must be evenly distributed across the image block
Flight lines must be parallel for accurate triangulation
Images in a strip must have uniform scale throughout
An object point, the camera perspective center, and its image point must lie on a single straight line (Correct answer)

Correct answer: An object point, the camera perspective center, and its image point must lie on a single straight line

The collinearity condition states that an object point, the camera's perspective center, and the corresponding image point must lie on the same straight line, which is the fundamental geometric basis of the photogrammetric equations.

Question 92: What is 'vertical datum' and why is it critical in photogrammetric elevation products?

The elevation of the base station used for GPS differential correction
The maximum allowable vertical error in the DEM product
The minimum flight altitude allowed by aviation regulations
The reference surface (e.g., NAVD 88, NGVD 29, ellipsoid) to which all elevations are referenced, determining how heights interoperate with other datasets (Correct answer)

Correct answer: The reference surface (e.g., NAVD 88, NGVD 29, ellipsoid) to which all elevations are referenced, determining how heights interoperate with other datasets

The vertical datum defines the reference surface (e.g., NAVD 88 in the US) to which all elevations are referenced; using an incorrect or undocumented datum causes systematic elevation offsets when data is integrated with other height information.

Question 93: What is 'pansharpening' in multispectral photogrammetric products?

Georeferencing a scanned historical map using modern imagery
Removing motion blur from images using deconvolution
Sharpening contours using a mathematical gradient filter
Fusing a high-resolution panchromatic image with lower-resolution multispectral bands to produce a high-resolution color image (Correct answer)

Correct answer: Fusing a high-resolution panchromatic image with lower-resolution multispectral bands to produce a high-resolution color image

Pansharpening fuses a high-spatial-resolution panchromatic (greyscale) image with coarser-resolution multispectral bands to produce a sharp, full-color image at the panchromatic resolution.

Question 94: What is 'stereoscopic exaggeration' in photogrammetric viewing?

The distortion introduced by incorrect lens calibration
The color enhancement applied to improve feature discrimination
The enhancement of image contrast in stereo viewing systems
The perceived amplification of vertical relief when the eye base is larger relative to the B/H ratio than normal human vision (Correct answer)

Correct answer: The perceived amplification of vertical relief when the eye base is larger relative to the B/H ratio than normal human vision

Stereoscopic exaggeration is the perceived amplification of terrain relief when the base-to-height ratio exceeds that of normal human stereo vision (approximately 1/30), making slopes appear steeper than they are.

Question 95: What is the purpose of 'edge enhancement' in photogrammetric image processing?

To detect GPS multipath errors along photo edges
To smooth orthophoto seams between adjacent strips
To sharpen boundaries between land cover classes for improved visual interpretation and feature extraction (Correct answer)
To increase radiometric resolution from 8-bit to 16-bit per channel

Correct answer: To sharpen boundaries between land cover classes for improved visual interpretation and feature extraction

Edge enhancement sharpens boundaries between features in imagery—such as roads, building edges, and field boundaries—improving visual clarity and automated feature extraction.

Question 96: What is the primary purpose of aerial triangulation in photogrammetry?

To measure the altitude of the aircraft during flight
To calculate the focal length of the camera
To determine the exterior orientation parameters of photographs without ground control at every photo (Correct answer)
To generate color-balanced orthophotos automatically

Correct answer: To determine the exterior orientation parameters of photographs without ground control at every photo

Aerial triangulation determines exterior orientation parameters by using a network of tie points and sparse ground control, eliminating the need for ground control at every photograph.

Question 97: What causes 'layover' in radar imagery, and can it affect photogrammetric products?

Layover in photogrammetry refers to GPS signal multipath errors
Layover is caused by atmospheric haze and degrades photogrammetric accuracy uniformly
In radar, layover occurs when tall objects lean toward the sensor; in photogrammetry, the analogue is relief displacement (Correct answer)
Layover is exclusive to multispectral sensors and does not affect photogrammetric products

Correct answer: In radar, layover occurs when tall objects lean toward the sensor; in photogrammetry, the analogue is relief displacement

Radar layover occurs when tall objects appear to lean toward the sensor due to the near-range compression of elevated objects; the photogrammetric analogue is relief displacement, where objects appear displaced from their true position.

Question 98: What does 'contour interval' mean in topographic map production?

The horizontal distance between adjacent contour lines
The vertical elevation difference between successive contour lines (Correct answer)
The time interval between adjacent flight lines
The pixel spacing in a digital elevation model

Correct answer: The vertical elevation difference between successive contour lines

Contour interval is the vertical elevation difference between consecutive contour lines on a topographic map, determining the level of vertical detail shown.

Question 99: The image scale (s) of a vertical aerial photograph with focal length f taken at flying height H above datum is expressed as:

s = f / H (Correct answer)
s = H / f
s = f × H
s = f + H

Correct answer: s = f / H

Image scale equals focal length divided by flying height above datum (s = f/H); a longer focal length or lower flying height produces a larger (more detailed) scale.

Question 100: What is the relationship between flying height (H), focal length (f), and image scale (1/S) in aerial photography?

Scale = H × f
Scale = H / f²
Scale = f² / H
Scale = f / H (image scale denominator S = H/f) (Correct answer)

Correct answer: Scale = f / H (image scale denominator S = H/f)

Image scale is f/H: a 152 mm focal length camera at 3,048 m flying height produces a 1:20,000 scale image, as scale = f/H = 0.152/3048 = 1/20,000.

Certified Photogrammetrist Exam

This certification validates an individual's expertise in the science and art of making measurements from photographs, especially for recovering the exact positions of surface points.

100

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180 min

Time Limit

70%

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