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These 10 free CPT questions are organized by exam domain, so you can see how each part of the Certified Photogrammetric Technologist blueprint is tested. Reveal the answer and explanation under each question.
The elevation errors at 36 independent checkpoints have a mean of +0.18 m and a sample standard deviation of 0.01 m. Errors are defined as model minus surveyed elevation. A technician cites the standard deviation as evidence of 1-cm vertical accuracy. What does the summary actually establish?
Correct answer: C - The errors show little scatter but a substantial positive vertical bias.
A surveyed target has a GNSS ellipsoidal height of 156.42 m. The compatible geoid model gives a geoid height of -31.18 m at that target. A terrain product reports an orthometric elevation of 187.63 m. For the elevation check, what signed error should be recorded using product minus reference?
Correct answer: D - +0.03 m
An analyst removes a block-wide offset by using six surveyed points to calculate a final translation. A separate set of 36 surveyed points has remained unused and unexamined until the corrected solution is fixed. Which set can independently test the corrected product?
Correct answer: A - The 36 points withheld from every adjustment and correction.
An aerial frame is correctly exposed at f/8 and 1/500 s, but forward-motion smear is excessive. Groundspeed, lighting, and sensor sensitivity must remain unchanged; the lens has adequate sharpness at f/5.6. Which setting approximately halves translational smear while preserving exposure?
Correct answer: C - f/5.6 at 1/1000 s
Pavement markings in a city orthomosaic agree with survey control, but surveyed roof corners are displaced away from the nadir locations of their source images. Camera orientations and the bare-earth elevation model check out, and overlapping images provide clear views of the roofs. Which processing change addresses the displacement?
Correct answer: B - Produce a true orthophoto using a building-inclusive DSM and occlusion handling.
A stereo pair has been rectified for a horizontal baseline, but verified conjugate points still have persistent vertical separation. The camera calibrations and left-right image order are correct. Before compiling elevations, the operator should:
Correct answer: A - Recheck relative orientation and rectification while preserving height-related horizontal disparity.
A vertical-frame survey requires native ground sampling no coarser than 4 cm. The camera has an 80-mm calibrated principal distance and 5-micrometer pixels. Terrain elevations range from 480 m to 760 m, and the camera will fly at one constant elevation in the same vertical datum. Using the vertical-camera approximation for locally horizontal ground, which listed camera elevation is the highest that meets the requirement throughout the block?
Correct answer: B - 1,080 m
A projective rectification of an oblique photograph reproduces surveyed dimensions on a flat factory wall. A loading canopy projects outward from that wall. To recover the canopy's three-dimensional geometry rather than its projection onto the wall, the technologist needs to:
Correct answer: D - Measure the canopy from oriented, convergent views that resolve its depth.
A self-calibrating adjustment of parallel, near-nadir flight strips has small image residuals. Independent checkpoints show little elevation error around the block perimeter but a smooth positive dome toward its center. The checkpoint survey and vertical reference have been verified. This combination most strongly indicates:
Correct answer: C - Coupling between camera calibration and terrain shape in a weak image network.
Stereo-measured points correctly locate a drainage channel's bottom and bank crests. In the resulting TIN, some triangles connect opposite banks and cut across the measured channel, creating false raised sections. Which intervention preserves the channel geometry?
Correct answer: A - Enforce breaklines along the thalweg and bank edges before retriangulating.
The CPT exam also covers these domains. Drill them in the full free practice test:
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