Aerial Imaging Flashcards
what does remote mean
from a distance
what does sensing mean
to view or perceive
what device can detect visual information from a distance
cameras
what do our eyes sense from a distance? or ears?
eyes - visual information
ears - sound waves
what device can sense sound waves from a distance
audio recorders
what is remote sensing
the acquisition of information about light energy emitted or reflected by an objection a long distance away
examples of devices that can do remote sensing
- aircraft
- satellite
- drone
who observed a solar eclipse using a camera obscura
Al hazen
what is a camera obscura
a dark chamber (a device that projects an image of the outside world onto a dark surface inside)
what is a camera obscura also called
pinhole camera
what is the limit of a camera obscura
the image that is observed will be the inversion of the real thing
what can be done to resolve the issue with a camera obscura
using a circular tablet in the dark chamber eliminates the issue of the image being inverted
who created the first photograph
Joseph Niepce
when was the first photograph taken
1826
when are stereoscopes invented
1830
what are stereoscopes
a device that uses two pictures of the SAME scene with a slight offset mounted side by side to give the impression of 3D
are the images used in a stereoscope of the same scene or different
MUST BE THE SAME
who takes the first aerial photograph and HOW
Gasper Felix Tournachon using a hot air balloon
who in the history of remote sensing is nicknamed Nadar
Gasper Felix Tournachon
who is the father of kite photography
arthur batut
how is Arthur Batut different from Gasper Tournachon
Batut was the first to take an aerial photo with a set timer so he did not have to manually capture the photo
Who used pigeons to take aerial photographs
Bavarian Pigeon Corp
where pigeons used in WWI and WWII
YES
what caused on increased interest in aerial reconnaissance
WWI
after WW II, what was the driving force of advancements in aerial photography
tensions between Russia and USA (Cold war)
what are examples of the advancements in aerial photography during cold war
- US military building U2 Spy Plane
- Mach 3
what was the Mach 3+ used for
strategic reconnaissance because it could travel long distances and at very high elevations
what started aerial photography in canada
when the British gifted military aircrafts and photography equipment to Canada
what were the first aerial images about in Canada
oil geologists and entomologists photographing a swampy section of the slave river
what was the first experimental survey in canada of
Ottawa
what was significant about the first experimental survey in Canada
ground based surveys usually took weeks/months to do but using aerial photography it took only hours/days
how many aerial photos were taken in canada by 1920
1200 with altitudes ranging up to 10 000 ft
when was the take off point of aerial photography in Canada
1921
what was fundamental for the completion of the st lawrence seaway
aerial surveys
how many aerial photographs has canada done in 100+ years
over six million photos
what are two aircrafts used for aerial photography in Canada
single engine Cessna to multi-engine Dash 7s
what continents have Canadian aerial photography crews not flown on, if any?
NONE - have flown on ALL of them
what type of camera is used for aerial photography
single lens
what is the focal length
distance between the lens and the film at focal plane
what are 3 imaging problems with aerial photography
- the plane is moving forward while imaging (create blur)
- turbulence causes place to pitch and roll (image is unfocused)
- image distortions
what was a solution to the imaging problem caused by turbulence
gyro-stabilized mounts that correct for pitch and roll
what was a solution to the imaging problem caused by the forward motion of plane
forward motion compensation
true or false:
aerial photographs have the same scale throughout the image
FALSE
principal point in aerial photograph
center of the photo
what point in an aerial photo has the LEAST distortion
principal point
what is relief displacement in aerial photography
an issue that causes tall objects to lean away from the principal point towards the edge of the photo
what removes the effects of relief displacement
orthorectification
what does orthorectification create
orthophotos with UNIFORM SCALE
what are true orthophotos
provide the appearance of looking straight down on all objects
three types of aerial photographs
- vertical
- low oblique
- high oblique
type of aerial photo (1)
vertical
type of aerial photo (3)
low oblique
type of aerial photo (2)
high oblique
how much tilt are in vertical photographs
3% or less
what is beneficial about vertical photographs
reduces image distortion
describe the scale in vertical photographs
nearly constant scale across the photo
what can causes changes in scale across a vertical photograph
changes in elevation in the photo
what are vertical photographs used for
- photogrammetry
- image interpretation
how much tilt is in low oblique photos
greater than 3%
is the horizon visible in low oblique photos? high oblique?
low - NOT visible
high - IS visible
what is beneficial about low oblique photos
creates a familiar perspective (what we would see out of a plane)
describe the scale of low oblique photos
scale is distorted (changes from top to bottom of image)
what type of photo has the largest change in scale across the photo
high oblique photos
three times of image colour
- panchromatic
- colour imagery
- colour infrared (CIR)
what is panchromatic colours
images that use only a portion of the visible spectrum to create a greyscale image
what is colour imagery
images that capture red, green and blue light to create true colour composites
what is colour infrared
images captured with film sensitive to infrared light NOT visible to the naked eye
what is colour infrared photos useful for
envi studies like vegetation health
what are photographs
projections of the 3d world onto a 2d surface
how are our eyes similar to a photo
each eye observes a 2d image
what is monocular vision
each eye observing a 2d image
what is the purpose of the brain in image identification
converts the image from each eye into a 3d image
what is binocular vision
the ability to use both eyes to see a single image and perceive depth
contrast monocular vs binocular vision
Monocular vision is seeing with one eye, while binocular vision is seeing with both eyes
what does binocular vision result in
depth perception
what is retinal disparity
each eye focuses on an object from a slightly different position
what is parallax
the difference in apparent position of an object viewed from two different positions
how does the brain reconstruct a 3d image
by fusing both images from our eyes
what is nadir
the point or line DIRECTLY below the collection instrument
how much overlap is there in images of the same flight line
60%
how much overlap is there in images of adjacent flight lines
20% to 40%
which photos are plotted on a national topographic system map
first
last
every 5th photo
how are photo centers represented
by small circles with straight lines connecting them
what is the objective of aerial images
to gain complete spatial coverage of a 3d area
what are stereo pairs
images overlap that create two different viewpoints
what does a stereo pair create
image parallax
what are fiducial marks
markers built that appear in the produced image
what is the principal point in regards to fiducial marks
intersection of the fiducial marks at the center of the image
what is the conjugate principal point
the location of the PP from one photo on the ADJACENT photo in the flight line
is the PP the same as Nadir
NO - there can be up to 3% tilt in an image so the principal point is not always the same across each flight line
how is scale represented
as a representative fraction
what is representative fraction
a fraction where one unit of the photo is equal to however many of the SAME unit on the ground
what is scale a function of
tilt and topography
what can cause variations in scale
tilt
what creates a range in distance from the camera
tilt
8 visual image interpretation
- pattern
- site and association
- size
- shadow
- shape
- texture
- tone
- time
