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Introduction to Aerial Photography Interpretation: 

Introduction to Aerial Photography Interpretation

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 Photography: 

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 Photography: 

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 A large format oblique camera Keystone’s Wild RC-10 mapping 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

Products: 

Products 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 Scale is printed at the top of a photo, usually as RF

Determining Photo Scale: 

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 =

Determining Photo Scale: 

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) where: h = Object height d = length of object from base to top r = distance from nadir to top of object

Calculating Object Heights: 

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 Shape Size Color/Tone Texture Pattern Site Association Shadow

Photointerpretation: Recognition Elements: 

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 Elements: 

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 Elements: 

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 Elements: 

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 Elements: 

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: 

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 Elements: 

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: Archaeology: 

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: Geology: 

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 own: 

Getting your very own USGS EROS Data Center Customer Services Sioux Falls, SD 57198 (605) 594-6151 email: custserv@edcserver.cr.usgs.gov web: http://edcwww.cr.usgs.gov/nappmap.html B&W paper contact prints - $6.00 CIR - $16.00 Helpful to know lat./long. of your area of interest

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