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CE203.final > final exam > Flashcards

final exam Flashcards

1
Q

What is the objective of photogrammetry?

A

derive the position (coordinates) and shapes of objects from imagery

2D to 3D transformation

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2
Q

List some of Photogrammetry’s fields of application.

A

topographic mapping, resource management, infrastructure management, medical, transportation, precision agriculture

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3
Q

Can you reconstruct object space from a single photograph? Illustrate your answer using
a simple sketch

A

No, you need two or more images to reconstruct the object space. NEED sidelap or overlap

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4
Q

What is the advantage of constructing object space from several images as opposed to
stereo-images

A

You can construct a 3D model

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5
Q

What are the main differences between analog and digital imagery? Discuss topics like
advantages, media, coordinate systems, sources of imagery, hardware, etc.

A

analog: film camera with film being measured in millimeters

digital: digital camera where image is made of equal sized pixels

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6
Q

What are the requirements for 3-D viewing of 2-D imagery?

A

1.at least 2 images from different locations
2. remove y-parallax
3. maintain x-parallax that is proportional to the height

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7
Q

What are the different techniques for stereo 3-D viewing? What are the requirements for
each method?

A

-Photogrammetric Plotters
-Anaglyph Glasses
-Polarized Glasses
-Synchronized Eyewear

Allow each eye to only view one image

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8
Q

What are the basic components of a camera?

A

lens, aperture, shutter, flim/digital sensor, body

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9
Q

lens

A

collects light and brings it to focus at the image plane

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10
Q

aperture

A

opening that controls the amount of light entering the camera

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11
Q

shutter

A

determines the time period during which the film/digital sensor will be exposed to light

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12
Q

film/digital sensor

A

light-sensitive media

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13
Q

body

A

light proof housing of the camera mechanism.

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14
Q

What is the typical dimension of the portion of the negative within the focal plane of an
aerial mapping camera?

A

9in x 9in

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15
Q

How are the camera components different for analog and digital cameras?

A

Analog cameras use film while digital cameras use digital sensors

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16
Q

List the major wavebands of the EM radiation. Which one is used in photogrammetry?

A

0.3-0.9
human eye
lidar
photography
thermal scanners

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17
Q

metric camera

A

cameras intended for precise mapping (internal characteristics are known and stable)

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18
Q

analog camera

A

the relationship between the film and lens/camera body changes as film is rolled inside the magazine

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19
Q

passive sensor

A

simply processes received signal from the surrounding environment, don’t need power to work (thermometer)

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20
Q

active sensor

A

send out a signal and react to the response, need their own power (RADAR & LiDAR)

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21
Q

What is the EM radiation used in LiDAR systems? Are they active or passive systems?

A

0.3-15 and active systems

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22
Q

Why is it important to reduce the aberration and distortion effects?

A

to increase the accuracy of the image

23
Q

aberration

A

spherical astigmatism, curvature of the field. coma & chromic aberrations (we want smaller aperture)

24
Q

What is the conceptual difference between physical and geometric optics?

A

geometric optics: treat light as a single beam and study its properties

physical optics: reflection and refraction

25
Q

Explain the issues addressed by the law of reflection.

A

The reflection law states that the incident ray, the surface normal, and the reflected ray lie in the same plane. The incident angle is equal to the reflection angle.

26
Q

Explain the issues addressed by the law of refraction.

A

Also known as Snell’s Law states that the incident ray, the surface normal, and the refracted ray lie in on one plane. nisin(i) = nrsin(r) where ni is the refractive index of the medium containing the incident ray and nr is the refractive index of the medium containing the refracted ray.

27
Q

nodal point

A

intersection of principal planes with the optical axis

27
Q

What is the significance of the critical angle?

A

It is the incident angle which causes a 90 degree angle of refraction. It is the largest angle of incidence for which refraction can still occur.

28
Q

focal point

A

the axial points where the images of axial objects at infinity are located

29
Q

focal legnth

A

the distance between the focal point and the corresponding nodal point

30
Q

optical axis

A

the rotation of the optical system that passes through the centers of curvature of surfaces comprising the lens system

31
Q

principal point

A

the intersection of the normal to the image plane through the perspective center with the image plane

32
Q

nadir point

A

the intersection of the plumb line (gravity) through the perspective center with the image plane

33
Q

What is the paraxial region and why is it of interest to us?

A

The hypothetical cylindrical narrow space surrounding the optical axis within which rays of light are still paraxial.
Assumptions made in geometric optics for image formation lead to inaccuracies that are proportional to the angle between a light ray and the optical axis.

34
Q

Classify the manifestations and the causes of various lens aberrations.

A

Spherical Aberrations: large aperture and/or off axial objects
Chromatic Aberrations: caused by different wavelengths of the incident light
Irregular Aberrations: caused by manufacturing flaws

35
Q

What are the differences between aberrations and distortions?

A

Aberrations will affect the precision of the final image coordinate measurements but distortions will affect the accuracy of the final image coordinate measurements

36
Q

What are the causes of radial lens distortion? List two of its characteristics.

A

It is when the light ray changes its direction after passing through the perspective center. It is caused by large off-axial angle and lens manufacturing flaws. They occur along a radial direction from the center of the image and increases as we move away from the optical axis.

37
Q

What causes de-centering lens distortion?

A

It is caused by misalignment of the components of the lens system. It has two components: radial component and tangential component

38
Q

Define the resolving power of an imaging system. List the factors that affect it.

A

measured by the number of line pairs per mm. It is affected by aberrations, depth of field, depth of focus, diffraction, film material, and motion blur.

39
Q

What is meant by the depth of field? What are the factors that affects it? How can it be improved for a given camera?

A

It is the distance in the object space within which the object point can be moved and still be in acceptable focus. It is affected by aperture, focal length, and distance from subject to camera.

40
Q

What is meant by the depth of focus? What are the factors that affects it? How can it be improved for a given camera?

A

it is the distance in front or behind the plane of best focus for a given object distance where the image is still in acceptable focus. It is affected by aperture, focal length, object distance, radius of the acceptable circle of confusion.

41
Q

What property does Snell’s law measure? Why is it important in photogrammetry?

A

It measures the relationship between angle of incidence and angle of refraction through different mediums. This is important to photogammetry because when light passes through different mediums, it could potentially cause errors.

42
Q

What is IMC (Image motion compensation)

A

In high-end or metric cameras, where to avoid blur the camera has a mechanism that causes the film to advance forward in the flight direction during exposure time

43
Q

What are the basic differences between negative, inverse, and positive films?

A

Negative Film: dark areas appear bright
Inverse Film: maintain same light intensity
Positive Film: image and object directions are in agreement

44
Q

What are the main differences between negative and diapositive B/W films?

A

Diapositive B/W films show the correct light/dark intensity in relation to the object capture on film while negative B/W film shows the opposite

45
Q

To filter out the blue color, what is the color of the used filter?

A

blue

46
Q

What is meant by the following terms; Resolving Power and Dynamic Range?

A

Resolving Power: number of line pairs per mm
Dynamic Range: also known as radiometric resolution is the ability of the sensor to quantify different amounts of energy at a specific waveband

47
Q

what are the factors that affect the resolving power of an analog camera? (6)

A

-lens aberrations
-diffraction
-depth of field
-depth of focus
-motion blur
-film material

48
Q

What are the factors that affect the Resolving Power of a digital camera? (6)

A

-lens aberrations
-diffraction
-depth of field
-depth of focus
-motion blur
-CCD/CMOS array

49
Q

What are the factors that affect the Radiometric Range of a digital camera?

A

-lens aberrations
-depth of focus
-diffraction
-pixel size
-motion blur

50
Q

What are the factors that affect the Radiometric Range of an analog camera?

A

-lens aberrations
-depth of focus
-diffraction
-motion blur

51
Q

What is the Dynamic Range of an 8 bits/pixel B/W digital camera?

A

256 shades of gray for a single pixel

52
Q

What is the dynamic range of a 24 bits/pixel color digital camera?

A

2^24 different colors

CE203.final (1 decks)

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