Section 5 Flashcards

(42 cards)

1
Q

What are the two types of geometric correction?

A

Image to image

Image to map/vectors

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2
Q

What is an internal geometric error?

A

Errors introduced by the remote sensing scanner or with earths rotation.

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3
Q

What is another term for internal geometric error?

A

Systematic distortions.

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4
Q

What are the six types of systematic distortions?

A
Scan skew
Mirror scan velocity
Panoramic distortion
Platform velocity
Earth rotation
Perspective
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5
Q

What are external geometric errors?

A

Movements by the aircraft like altitude change

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6
Q

Name and define the two types of external geometric errors

A

Altitude changes, attitude changes (roll pitch yaw)

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7
Q

What does changing altitude effect?

A

The scale of an image

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8
Q

What is more likely to have an attitude change, satellites or airplanes?

A

Airplanes

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9
Q

What is a way to prevent attitude distortions?

A

Gyro-stabilization equipment

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10
Q

What is the roll of a plane? And how will this effect an image?

A

Side to side rotation of a plane (wings dipping) and it will cause compression and expansion in the pixels of left and right side of the image

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11
Q

What is the pitch of an airplane? And what does it do to images?

A

The nose or tail of a plane dipping and it causes expansion and contraction in the pixels on the top and bottom of an image

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12
Q

What is the yaw of an image? And how does this effect an image?

A

This is the rotation directionally and it changes the rotation of the pixels

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13
Q

What is image skew in a satellite?

A

As earth rotates as a satellite scans the earth the pixels won’t align properly

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14
Q

What is image to image geometric correction?

A

When you need to compare and image to another the master slave correction will be between two images taken in the same location

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15
Q

What is image to map geometric correction?

A

An image is tied to a map that has the same projection

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16
Q

What is rectification?

A

The linking of a slave image to a master image

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17
Q

What is resampling?

A

The transfer of data from the slave image to the new geometrically corrected images

18
Q

What is geometric correction?

A

Assigning coordinates to an image to make it comparable to another image

19
Q

What is a GCP and what are they used for?

A

Ground control points. They are used to correct the slave image to the master image

20
Q

True or false

GCPs should be clustered in the important part o an image

A

False they should be uniformly distributed

21
Q

What are the two rules of selecting GCPs?

A

Points should be permanent and distinctive

22
Q

What makes correcting images from airborne sensors more difficult?

A

Altitude can be different scan line to scan line

23
Q

What is a frame capture?

24
Q

What formula checks the accuracy of the GCPs?

A

Root mean square error
RMS
This tells how off your points are from eachother

25
When geometrically correcting an image what is the step after selecting GCPs?
Generating a new project based on these points
26
What are three ways to generate a new project.
Conformal transformation Affine transform (first order polynomial) Higher order polynomial transformation
27
What is a conformal transform?
A geometric correction used to translate an image in one coordinate system to another. Image must be geometrically correct
28
Why is a conformal transform used? How many GCPs does it use?
Scale changes, rotation of images, translation to 3D. 2 GCPs
29
What is a first order transformation/affine transformation?
Similar to conformal, but image can only be changed in the x and y directions.
30
How many GCPs are needed for a first order polynomial?
3
31
What is a high order polynomial transformation?
A geometric correction that does not preserve parallel lines or shape
32
How many GCPs does a high order polynomial require?
6 or more
33
What is another term for higher order polynomial?
Rubber sheeting. This allows for differing geometry
34
What is the downside of higher order polynomial?
Edges of the image become unstable.
35
What are the three types of image resampling?
Nearest neighbour Bilinear interpolation Cubic convolution
36
What does the nearest neighbour resampling method do?
It preserves the true values of the original data. It is referred to as a zero order interpolator
37
Describe a bilinear interpolation resampling method
It is referred to as a first order interpolator. This method changes the original values by averaging pixel values
38
What is the advantage of using bilinear over NN?
There is a degree of smoothing to the image
39
What is the disadvantage of bilinear?
The original data numbers are not preserved
40
Describe how cubic convolution works.
It is an improvement on the bilinear in that more pixels are averaged to create new values
41
How is cubic better than bilinear?
There is less blur to the image
42
When is it better to use an NN resampling method?
When you will be taking measurements from the data