Introduction to Aerial Photo Interpretationgrel.ist.edu.pk/lms/pluginfile.php?file=/2183/mod... ·...

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Introduction to Aerial Photography

Transcript of Introduction to Aerial Photo Interpretationgrel.ist.edu.pk/lms/pluginfile.php?file=/2183/mod... ·...

Introduction to Aerial Photography

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)

Normal color

False-color infrared

Normal color False-color infrared

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

Extraction of Building Infrastructure

based on orthophotographs

Orthophotograph draped over a DEM

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

orth

orectifica

tion

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.

Aerial Cameras

A large format oblique

camera

Keystone’s Wild RC-

10 mapping camera

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

CIR and True Color Film Type

Examples

CIR True Color

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