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Introduction to Aerial Photo Interpretationgrel.ist.edu.pk/lms/pluginfile.php?file=/2183/mod... ·...
Transcript of Introduction to Aerial Photo Interpretationgrel.ist.edu.pk/lms/pluginfile.php?file=/2183/mod... ·...
History of Aerial Photography
• 1858 - Gasparchard Tournachon photographs Bievre (outside Paris) from a balloon
• 1860 - James Black photographs Boston Harbor from a tethered balloon (earliest existing - perhaps first in US)
Boston Harbor 1860
History of Aerial Photography
• US Civil War - Union General George McClellen photographs confederate troop positions in VA.
• 1882 - E.D. Archibald, British Meterologist takes first kite photograph
• 1903 - Pigeon cameras
• 1906 - George Lawrence photographs San Francisco after great earthquake and fire
History of Aerial Photography
• 1906 - George Lawrence photographs San Francisco after great earthquake and fire
“San Francisco in Ruins,” by George Lawrence, was taken
with a kite 6 weeks after the Great 1906 Earthquake.
History of Aerial Photography
• 1909 - Wilbur Wright and a motion picture photographer are first to use an aircraft as a platform - over Centocelli, Italy
• WW2 - Kodak develops camouflage-detection film
– used with yellow filter
– sensitive to green, red, NIR
– camouflage netting, tanks painted green show up as blue instead of red like surrounding vegetation
History of Aerial Photography • 2002 - Field workers document the effects of the M7.9
Denali Fault Earthquake with digital cameras from planes and helicopters
Mosaic view of rock avalanches across Black Rapids
Glacier. Photo by Dennis Trabant, USGS; mosaic by
Rod March, USGS.
Aerial view of the Trans-Alaska
Pipeline and Richardson
Highway. Rupture along the fault
resulted in displacement of the
highway. Photo by Patty Craw,
DGGS.
History of Aerial Photography
• 2006 - Effie Kokrine Charer School Students take digital “flotographs” at Twin Bears Camp, Alaska
Types of vantage points to acquire photographs
• Vertical vantage points
• Low-oblique vantage points
• High-oblique vantage points
Goosen
ecks of
the San
Juan
River
in Utah
Vertical Aerial Photography
Jensen, 2000
Most are vertical aerial photography
Low-oblique photograph of a
bridge on
the Congaree River near
Columbia, SC.
Low-oblique Aerial Photography
Jensen, 2000
High-oblique photograph
of the grand Coulee Dam
in Washington in 1940
High-oblique Aerial Photography
Jensen, 2000
Color Science
• Additive primary colors : – Blue, Green, and Red
• Subtractive primary colors (or complementary colors): – Yellow, Magenta, and Cyan
• Filters (subtract or absorb some colors before the light reaches the camera): – Red filter (absorbs green and blue, you can
see red)
– Yellow (or minus-blue) filter (absorbs blue, allows green and red to be transmitted, which is yellow)
– Haze filter (absorbs UV)
additive
Subtractive
Types of photographs
• Black and white photographs – Panchromatic (minus-blue filter used to eliminate UV and blue
wavelengths)
– IR (IR-sensitive film and IR only filter used to acquire photographs at 0.7- 1.0 m )
– UV (at 0.3-0.4 m, low contrast and poor spatial resolution due to serious atmospheric scattering)
• Color photographs – Normal color (Haze filter used to absorb UV and create true color 0.4-
0.7 m, or blue, green, red)
– IR color (Yellow filter used to eliminate blue and create IR color (or false-color infrared) of 05-1.0 m, or green, red, and IR)
– 4 bands (blue, green, red, and IR)
Scale of photographs
Image size/ real
world size :
S = ab/AB
Focal length/
altitude above
ground:
S = f / H
Scale (2)
1’ = 12 ”
S = 0.012/ (6 x 12) = 1/6000 S = f / (H-h)
Max scale, minimum scale, and
average or nominal scale
In real world
In the image
Digital Cameras
• Use an area array of solid-state charge-coupled-device (CCD) detectors. The detectors are arranged in a
matrix format with m
columns and n rows.
• Analog (continuous) signals (voltage) are converted into (discrete) digital brightness value (DN)
Orthophotographs and digital orthoimagery
• An aerial photograph that has all the distortions due to camera tilt, scale, oblique, and surface relief.
• Photograph after corrected by ground control points (x, y, z) or digital elevation model (DEM), namely orthorectification, called orthophotograph, orthophoto, or digital orthoimagery.
• Not as photographs, they have different scales in different terrain relief, orthophotos have only one scale, no distortion, and have true distance, angle, and area. Orthophotos can be directly input into GIS as basemap or for interpretation.
Orthorectification of SIMBA camera photos in assisting ASPeCt sea ice observations
Blake et al. to be submitted
Orthorectified
photo
PhD student
Blake
Weissling in
SIMBA Oct-
Nov. 2007
Satellite photographs
• Extensive collections of photographs have been acquired from manned and unmanned Earth or Mars-orbiting satellites. – Beginning in 1962, USA acquired photographs of moon for Apollo mission – 1995, USA declassified intelligence satellites photographs of Sino-Soviet
acquired 1960-1972 at 2-8 m resolution. – 2000, Russia launched satellites acquired photographs of 2 meter resolution – 1999, Mars Orbiter Camera (MOC) onboard the Mars Global Surveyor (MGS)
of NASA acquires Mars photographs with 1.2 – 12 m resolution – 2003, High Resolution Stereo Camera (HRSC) on board the ESA Mars Express
acquires Mars photographs with 10 m resolution, selected areas will be imaged at 2 meters resolution.
– 2005, High Resolution Imaging Science Experiment (HiRISE) on board NASA MRO (Mars Reconnaissance Orbiter) acquires Mars photographs with up to 25 cm resolution.
Types of Air Photos
High (horizon) &
Low (no horizon)
Oblique
High oblique photo by Austin
Post. Oasis Branch, Baird
Glacier, Alaska 08/09/61.
Types of Air Photos
• Vertical
• Stereo/3D
Color infrared (CIR)
stereopair of the
Galbraith Lake, Alaska
area.
Film Types
• Panchromatic (B& W)
– most often used in photogrammetry
– cheap
• Color
– easy to interpret
– fuzzy due to atmospheric scattering
More Film Types
• Black & White Infrared
– popular for flood mapping (water appears very dark)
– vegetation mapping
– soils - dry vs. moist
• False Color Infrared (CIR, Standard False Color)
– vegetation studies
– water turbidity
Products • Contact Prints - 9”x 9”s
• Film Positives - Diapositives
• Enlargements
• Mosaics
• Indices (a reference map for air photo locations)
• Rectified Photos (can import into a GIS)
• Orthorectified Photos (can import into a GIS)
• Digital Orthophotos (can import into a GIS)
Printed Information/Annotation • Along the top edge, you’ll find:
– Date of Flight
– Time - (optional - beginning/end of flight line)
– Camera focal length in mm (optional - frequently 152.598 mm = 6”)
– Nominal scale (RF)
– Vendor/Job #
– Roll #, Flight line & Exposure #
Determining Photo Scale
• Sometimes (at beginning and end of a flight line) Nominal Scale is printed at the top of a photo, usually as RF
Determining Photo Scale
• More likely you will have to compute scale using ruler, map, calculator and this formula
1
(MD)(MS)/(PD)
where:
MD = distance measured on map with ruler (cm or in)
MS = map scale denominator (e.g., 24,000 for USGS Quads)
PD = photo distance measured in same units as map distance
RF =
No scale here….
Determining Photo Scale
• You can also roughly estimate scale from cultural features if there are any in the image (problematic in Alaska), e.g., tracks, athletic fields, etc.
Determining Photo Orientation
• Labels and annotation are almost always along northern edge of photo
• Sometimes eastern edge is used
• Only way to be certain is to use a map
Photointerpretation: Recognition Elements
Shape Size Color/Tone Texture
Pattern
Site
Association
Shadow
Photointerpretation: Recognition Elements
• Shape
– cultural features - geometric, distinct boundaries
– natural features - irregular shapes and boundaries
– Shape helps us distinguish old vs. new subdivisions, some tree species, athletic fields, etc.
The pentagon Meandering river
in Alaska
Interior Alaskan
village (note airstrip
near top of image)
Photointerpretation: Recognition Elements
• Size
– relative size is an important clue
– big, wide river vs. smaller river or slough
– apartments vs. houses
– single lane road vs. multilane
Photointerpretation: Recognition Elements
• Color/Tone
– coniferous vs. deciduous trees
CIR - Spruce forest
(black) with some
deciduous (red)
trees.
CIR – Deciduous
(leafy) vegetation
(red).
CIR- Mixed spruce
And deciduous forest
on hillside with tundra
in valley bottom.
Photointerpretation: Recognition Elements
• Color/Tone – Turbidity - relative amounts of sediment in water
– Vegetation presence or absence
CIR – The big, light blue river in the lower
part of the image is the Tanana River. It
carries fine particles eroded by glaciers in the
Alaska Range.
The smaller dark blue river flows south from
top of the image to the Tanana River. It is
fed by surface runoff and groundwater
sources and does not carry much sediment.
Unvegetated gravel bars look bright bluish
white.
Photo by Maria Sotelo
Relatively clear Chena
River water
Turbid Tanana River water
Photointerpretation: Recognition Elements
• Texture
– coarseness/smoothness caused by variability or uniformity of image tone or color
– smoothness – tundra, swamps, fields, water, etc.
– coarseness - forest, lava flows, mountains etc.
CIR- Marshy
tundra with many
small ponds.
CIR - Bare rounded
Mountains (blue)
surrounded by tundra
and lakes.
CIR - Tundra showing
drainage pattern
Photointerpretation: Recognition Elements
• Pattern – overall spatial form of
related features
– repeating patterns tend to indicate cultural features - random = natural
– drainage patterns can help geologists determine bedrock type
A dendritic pattern is characteristic
of flat-lying sedimentary bedrock
Photointerpretation: Recognition Elements
• Site – site - relationship of a
feature to its environment
– differences in vegetation based on location: • In interior Alaska, black
spruce dominant on the north side of hills and deciduous trees on the south side.
• Vegetation is often has different characteristics by rivers than away from them
Meandering
Alaskan river
Interior Alaskan
hillside
N
Photointerpretation: Recognition Elements
• Association
– identifying one feature can help identify another - correlation
The white cloud and
black shadow have
the same shape, they
are related
The long straight airstrip near
the top of the image indicates
that there might be a village or
settlement nearby
Photointerpretation: Recognition Elements
• Shadows
– shadows cast by some features can aid in their identification
– some tree types, storage tanks, bridges can be identified in this way
– shadows can accentuate terrain
The mountain ridge on
the right side of this image
is accentuated by shadow
Getting your very own GeoData Center, UAF Geophysical Institute
(907) 474-7487 or (907) 474-7598 (8am to 5 pm Alaska time)
email: [email protected] or [email protected]
web: http://www.gi.alaska.edu/services/geodata
10”x10” CIR contact prints prices per frame - $18.00 (other
sizes available)
Digital files – low resolution (300 dpi) $12.00, high
resolution (1200 dpi) $51.00 (other resolutions available)
Contact the GeoData Center to request images. A staff
person will find the imagery and respond to your request.
Alternatively, browse the website and make a request based
on what you find. There are more images in the GeoData
archive than what you will see posted on the website.
Helpful to know lat./long. of your area of interest
Getting your very own USGS EROS Data Center
(800) 252-4547 (8am-4pm central time)
email: [email protected]
web: http://edc.usgs.gov/
• Digital files B&W or CIR prices per frame – medium resolution $3.00, high resolution $30.00 (other resolutions available)
• Prints not available, but, contact information is available on the USGS website to direct people to vendors who can make prints from the digital data from USGS
• Requires using Earth Explorer to web search for Alaskan imagery http://edcsns17.cr.usgs.gov/EarthExplorer
• Helpful to know lat./long. of your area of interest