Ariel Photogrametry

Question 1

What are the advantages of classic photogrammetry?(5)

Answer 1

1. Contactless Measurements
2. Large range of sizes
3. Short time of Observation
4. 3-D analysis
5. Extensive Documentation

Question 2

What are the cons of classic photogrammetry?(3)

Answer 2

1. Sufficient Illumination required
2. Sufficient Visibility Required
3. Expensive Technology

Question 3

What are the 3 types of data acquisition?

Answer 3

Terrestrial, Aerial, and Satellite

Question 4

What are the four types of images?

Answer 4

• Single Image (Orth projection)
• Image Pair (Stereo Triangulation)
• Image Block (Block Triangulation)
• Image Sequences (Movement)

Question 5

What are the three technology levels of Photogrammetry?

Answer 5

Analog, Analytical, and Digital

Question 6

What is a necessity for ortho image generation?

Answer 6

A surface model

Question 7

What are Vector Products / Orthophoto useful for?

Answer 7

Map updates and plotting of sealed areas

Question 8

What is DTM and what is it useful for?

Answer 8

Digital Terrain Model, useful for wire frame representation, 3d Visualization and height variation

Question 9

What is the pinhole camera defined by?

Answer 9

Interior orientation
- Calibrated Focal Length
- Perspective center

Question 10

What are three important features of working of pinhole camera?

Answer 10

• Image rays are straight lines
• Perspective center as point
• Image points in a plane

Question 11

What are some model errors for pinhole cameras (5)?

Answer 11

• Distortion
• Blurring caused by diffraction
• Lens errors
  
  • spherical aberration
  • chromatic aberration
• Blurring caused by motion
• Filter / Color

Question 12

What is the Formula for ground sampling distance?

Answer 12

GSD = \delta Pix’ h_g/c’ = \delta pix m_b

where \delta Pix’ = size of pixel on sensor

h_g = height above ground

c’ = chamber constant

Question 13

What is formula for Image scale M_b?

Answer 13

M_b = c’ / h_g

Question 14

What is formula for image scale figure m_b?

Answer 14

m_b = 1/ M_b = h_g/c’

where M_b = image scale
h_g = height above ground
c’ =chamber constant

Question 15

How much larger is minimum recognition size usually?

Answer 15

4 - 5 times the GSD

Question 16

What is the formula for swath width?

Answer 16

S = s’ h_g/c = s’m_b

Question 17

What is the formula for position error?

Answer 17

delta r = delta h tan alpha = delta h r’/c’

Question 18

How do you reduce radial displacement?

Answer 18

Bigger calibrated focal length

Question 19

What are direct geo-references?(6)

Answer 19

• Directly measuring position and altitude
• GNNS Global Navigation Satellite Systems
• Inertial Measurement Units IMU
• Star Tracker
• Position is fixed in parallel data acquisition
• Synchronization Necessary

Question 20

What are Indirect Geo References? (5)

Answer 20

• Computing absolute position from image data
• Spatial Resection / Bundle Block adjustment
• Needed are known points and Ground Control Points
• Position is computed in post-processing
• Sufficient amounts of known points neccessary

Question 21

What is photogrammetry?

Answer 21

The science of obtaining reliable information about the earth and its environment using non-contact sensors.

Question 22

What are analog ariel images useful for?

Answer 22

Updating building footprints

Question 23

What is GSD useful for?

Answer 23

For getting an estimation of the resolution of the system

Question 24

What is swath width important for?

Answer 24

Satellites