aerial photography

Question 1

platform

Answer 1

the vehicle the structure or vehicle

Question 2

spaceborn

Answer 2

185 km and higher
- most satellites and spaceships

Question 3

airborn

Answer 3

0.5km - 12km
- helicopters and airplanes

Question 4

ground based

Answer 4

150m
- mostly drones

Question 5

sensors

Answer 5

taking some kind of digital image – carried by platforms
- camera
- multi-spectral sensors
- LiDAR
- Radar

Question 6

today: aerial photography

Answer 6

platform = plane
sensor = camera

Question 7

early platforms used for aerial use

Answer 7

• balloons
• kites
• pigeons

Question 8

aerial surveillance: original use

Answer 8

developed as a military surveillance technology

Question 9

camera systems

Answer 9

dark box + small hole to let light in + light sensitive medium (now: digital sensors) that record how much light is let in when the hole is opened
- focus and exposure settings affect photo quality

Question 10

how much light you let in

Answer 10

focus + exposure
- Distance from objects being photographed
Exposure: correct amount of light is being let in

Question 11

nadir line

Answer 11

directly below aircraft; ground trace of aircraft

Question 12

endlap

Answer 12

space between two photos

Question 13

principle point

Answer 13

Point @ center of the photo, looking directly down from the aircraft

Question 14

how airphotos are taken

Answer 14

along flight lines

Question 15

air photo angles

Answer 15

oblique and vertical

Question 16

oblique

Answer 16

perpendicular to the ground
- more natural, makes interpretation easier
- Useful in urban mapping + disaster assessment
- more distortion

Question 17

vertical

Answer 17

used for terrain mapping + photogrammetry

Question 18

scale

Answer 18

defines the relationship between distance on a map and distance in the real world

Question 19

small vs. large school

Answer 19

small scale: further away; features look SMALLER
large scale: closer; features are LARGER

Question 20

scale calculation: actual measurements

Answer 20

map distance / ground distance

Question 21

scale calculation: other option

Answer 21

scale = camera focal length / flying height above terrain

0 as height increases, the scale gets smaller

Question 22

focal length

Answer 22

distance between optical sensor of lens & camera sensor
- Tells us about the angle of view + magnification

Question 23

angel of view

Answer 23

How much of the image is captured

Question 24

magnification

Answer 24

how big the features are

Question 25

types of distortion

Answer 25

- relief displacement - terrain variability - camera tilt distortion

Question 26

benefit of distortion

Answer 26

can be helpful in understanding what we see

Question 27

relief displacement

Answer 27

- location of tall objects displaced from their true location - amount and direction of displacement depends on object's location in a photo (anything not at principle point is distorted)

Question 28

terrain variability

Answer 28

-scale of map differs across elevations - When you have changes in elevation, the distance between the scale and the image being captured is different

Question 29

camera tilt distortion

Answer 29

-airplanes collecting airphotos dont always fly perfectly straight - camera tilt makes views slightly oblique, causing distortion

Question 30

orthophoto

Answer 30

- air photo that has been geometrically corrected to a constant scale - removes distortion due to uneven terrain, camera tilt - objects appear in their true locations

Question 31

what orthophoto is used in

Answer 31

- Creating maps - Measuring true distances bc it’s a more accurate measure of the earth's surface

Question 32

photogrammetry

Answer 32

info about 3D features - science and technology of obtaining spatial measurements from photographs

Question 33

visual interpretation

Answer 33

information about what's in a photo - identification of objects to generate maps and reports of observations - use characteristics of images; shape, size, pattern, tone, texture, shadows, site association

Question 34

stereoscopic vision

Answer 34

how we see in 3D - With our eyes: having 2 images allows us to detect depth and dimension - overlap between pairs of air photos allow 3D visualization

Question 35

image parallax

Answer 35

things that are farther appear to move less, and things that are closer appear to move more - apparent change in relative positions of objects caused by change in viewing position

Question 36

photo interpretation challenges

Answer 36

- overhead, unfamiliar perspective - unfamiliar and variable scales and resolutions - use of wavelengths outside the visible spectrum

Question 37

color (use of characteristics)

Answer 37

Tone: brightness of objects; how dark or like Hue: the color family

Question 38

pattern (use of characteristics)

Answer 38

the repeated pattern of a feature

Question 39

texture (use of characteristics)

Answer 39

frequency of tonal change; frequency of change in brightness or hue - How smooth or coarse is an image feature

Question 40

shadows (use of characteristics)

Answer 40

- Shadows can give insight into what something may be when our overhead perspective is inadequate

Question 41

site (use of characteristics)

Answer 41

Knowing something about the place you're studying something in provides much more indication into what something may be