Certified Photogrammetrist Photogrammetric Product Generation

Question 1

What is a 'true orthophoto' as distinct from a standard orthophoto?

Accepted Answer

An orthophoto corrected for building lean using a surface model of all above-ground features (DSM), so building walls do not appear in the image

Answer

An orthophoto produced using only ground control points without GPS assistance

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A color-balanced orthophoto with radiometric corrections applied

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An orthophoto produced from satellite imagery rather than aerial photography

Question 2

What is 'differential rectification' in orthophoto production?

Accepted Answer

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

Answer

Adjusting color differences between overlapping photographs

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Correcting GPS positions using a reference base station

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Removing systematic sensor distortions using a flat-field calibration

Question 3

What does 'contour interval' mean in topographic map production?

Accepted Answer

The vertical elevation difference between successive contour lines

Answer

The horizontal distance between adjacent contour lines

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The time interval between adjacent flight lines

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The pixel spacing in a digital elevation model

Question 4

For USGS National Map Accuracy Standards, what horizontal accuracy is required for a 1:24,000-scale map?

Accepted Answer

±12.2 meters (40 feet) at the 90% confidence level

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±5 meters at the 90% confidence level

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±1 meter at the 95% confidence level

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±50 meters at the 68% confidence level

Question 5

What is an 'orthomosaic' in photogrammetric production?

Accepted Answer

A single seamless orthophoto created by mosaicking (stitching) multiple overlapping orthophotos together

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A mosaic of ground control point sketches

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A color mosaic combining different spectral bands into a composite image

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A terrain model created by combining multiple stereomodels

Question 6

What is 'seam line generation' in orthomosaic production?

Accepted Answer

The process of defining boundaries between adjacent orthophotos in a mosaic to minimize visible transitions

Answer

Drawing boundaries between map sheets

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Detecting cracks in the terrain surface from elevation data

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Separating vegetated from non-vegetated areas automatically