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Introduction to Aerial Photography Interpretation 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

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history of 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 photography3
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
  • 1906 - George Lawrence photographs San Francisco after great earthquake and fire
history of aerial photography4
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 (0.7 - 0.9 m)
    • camouflage netting, tanks painted green show up as blue instead of red like surrounding vegetation
types of air photos
Types of Air Photos
  • High (horizon) & Low (no horizon) Oblique
  • Vertical
  • Stereo/3D
aerial cameras
Aerial Cameras

Keystone’s Wild RC-10 mapping camera

A large format oblique camera

film types
Film Types
  • Panchromatic (B& W)
    • most often used in photogrammetry
    • cheap
  • Color
    • easy to interpret
    • fuzzy due to atmospheric scattering
more film types
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
  • Contact Prints - 9”x 9”s
  • Film Positives - Diapositives
  • Enlargements
  • Mosaics
  • Indices
  • Rectified Photos
  • Orthorectified Photos
  • Digital Orthophotos
printed information annotation
Printed Information/Annotation
  • Along the top edge, you’ll find:
    • Date of Flight - always top left
    • Time - (optional - beginning/end of flight line)
    • Camera focal length in mm (frequently 152.598 mm = 6”)
    • Nominal scale (RF)
    • Vendor/Job #
    • Roll #, Flight line & Exposure # (always top right)
determining photo scale
Determining Photo Scale
  • Sometimes (at beginning and end of a flight line) Nominal Scaleis printed at the top of a photo, usually as RF
determining photo scale12
Determining Photo Scale
  • More likely you will have to compute scale using ruler, map, calculator and this formula




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 =


Variation in Scale

Tilt causes variation within a single photograph.

Scales are different on either side of the tilt.

FOR 220 Aerial Photo Interpretation and Forest Measurements

determining photo scale14
Determining Photo Scale
  • You can also roughly estimate scale from cultural features, e.g., tracks, athletic fields, etc.
determining photo orientation
Determining Photo Orientation
  • Labels and annotation are almost always along northern edge of photo
  • Sometimes eastern edge is used
  • Airport runway number x 10 gives you magnetic azimuth (to closest 10)
  • Only way to be certain is to use a map
calculating object heights
Calculating Object Heights
  • Object heights can be determined as follows:
    • calculate flight altitude (H)

by multiplying the RF denominator by the focal length of the camera

    • h = d/r(H)


h = Object height

d = length of object from base to top

r = distance from nadir to top of object

calculating object heights17
Calculating Object Heights
  • Stereoscopic Parallax
  • Parallax bar
  • Parallax wedge
  • Shadow length
    • object must be vertical
    • on level ground
    • height of another object is known or sun angle and time of day are known

Calculating the height of the Washington Monument via stereo parallax

photointerpretation recognition elements
Photointerpretation: Recognition Elements
  • Pattern
  • Site
  • Association
  • Shadow
  • Shape
  • Size
  • Color/Tone
  • Texture
photointerpretation recognition elements19
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.
photointerpretation recognition elements20
Photointerpretation: Recognition Elements
  • Size
    • relative size is an important clue
    • apartments vs. houses
    • single lane road vs. multilane
    • horse tracks vs. runner’s tracks
photointerpretation recognition elements21
Photointerpretation: Recognition Elements
  • Color/Tone
    • irrigated vs. dry fields, coniferous vs. deciduous trees

An algae bloom in color

An algae bloom in CIR

photointerpretation recognition elements22
Photointerpretation: Recognition Elements
  • Texture
    • coarseness/smoothness caused by variability or uniformity of image tone or color
    • smoothness - crops, bare fields, water, etc.
    • coarseness - forest, lava flows, etc.
    • even-aged vs. old growth

Helyer Woods and points south

photointerpretation recognition elements23
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 elements24
Photointerpretation: Recognition Elements
  • Site
    • site - relationship of a feature to its environment
    • citrus on hillside, Atlantic. white cedar in stream corridor
  • Association
    • identifying one feature can help i.d. another - correlation
    • cooling towers, HT lines => reactor vessels
photointerpretation recognition elements25
Photointerpretation: Recognition Elements
  • Shadows
    • shadows cast by some features can aid in their i.d.
    • some tree types, storage tanks, bridges can be identified in this way
    • shadows can also accentuate terrain

Powerline transmission towers

applications archaeology
Applications: Archaeology
  • Archaeologists and historical geographers can sometimes identify features hidden for centuries
    • Soil marks
    • Crop marks
      • positive
      • negative
    • Shadow marks
    • Snow marks

Above: Positive crop mark

Below: Negative crop mark

applications archaeology27
Applications: Archaeology

Soil marks in an English field

applications soils
Applications: Soils
  • Once bedrock geology and surface geology are known, a soil scientist can classify soil types based on soil tone, slope, etc.

Soil survey

applications agriculture
Applications: Agriculture
  • Census and inventory
    • monitor production
    • predict yields
    • plan for shortfall
    • search for arable lands
applications geology
Applications: Geology
  • Geologic mapping
    • Different drainage patterns can reveal what type of geology is present
    • Folds and faults are sometimes more recognizable from the air

San Andreas fault, Carrizo Plain, CA

applications geology31
Applications: Geology
  • Mineral, hydrocarbon, and groundwater exploration
  • Hazards - landslide and earthquake fault assessment

Berkeley CA’s Hayward fault running diagonally from lower left to upper right

applications forestry
Applications: Forestry
  • Forest type maps - sometimes down to species level
  • Appraisal of damage due to fire, insects, and disease
  • Timber volume estimates
  • Wildlife habitat management
air photo acquisition
Air Photo Acquisition
  • Optimal to fly late morning
    • low wind
    • clear sky
    • minimal shadows
  • What time of year?
    • March/April for photogrammetry
    • Summer for vegetation studies
problems with aerial photography
Problems with Aerial Photography
  • Clouds, haze, shadows/sun angle, snow
  • Distortion
    • tip & tilt
    • relief distortion
    • radial distortion
  • Limited to 0.3 - 0.9 m (UV-NIR)
  • Storage and handling can be a problem
getting your very own
Getting your very own
  • USGS National Aerial Photography Program (NAPP) successor to National High Altitude Photography Program (NHAP) has coverage of lower 48
  • NHAP CIR - 1:58K, Panchro - 1:80K
  • NAPP CIR - 1:40K, some panchro
    • approximately 334,000 photos
    • updated every 5 years (in theory)
getting your very own36
Getting your very own

USGS EROS Data Center

Customer Services

Sioux Falls, SD 57198

(605) 594-6151



  • B&W paper contact prints - $6.00 CIR - $16.00
  • Helpful to know lat./long. of your area of interest