Chapter 3 Introduction to airphoto interpretation Introduction to Remote Sensing Instructor: Dr. Cheng-Chien LiuCheng-Chien Liu Department of Earth Science

Chapter 3Chapter 3

Introduction to airphoto interpretationIntroduction to airphoto interpretation

Introduction to Remote SensingInstructor: Dr. Cheng-Chien Liu

Department of Earth Science

National Cheng-Kung University

Last updated: 16 April 2003

3.13.1 Introduction Introduction

Airphoto interpretation:Airphoto interpretation:• raw data human brain processing

information communicate

HistoryHistory• Balloon photographs (1858)• WWI military reconnaissance tool• WWII CD film• After WWII wide spread

3.2 fundamentals of airphoto 3.2 fundamentals of airphoto interpretationinterpretation

Photo interpreterPhoto interpreter• Training• Experience• Keen power of observation coupled with imagination &

patience• Thorough understanding of the phenomenon• Knowledge of the geographic region

Supporting materialsSupporting materials• Maps• Field observations

3.2.1 elements of airphoto 3.2.1 elements of airphoto interpretationinterpretation

Airphoto interpretation departs from daily Airphoto interpretation departs from daily imageimage• The portrayal of features from an overhead, often

unfamiliar perspective• outside visible range• Unfamiliar scales and resolutions

Basic characteristics:Basic characteristics:• Shape• Size• Pattern

3.2.1 elements of airphoto 3.2.1 elements of airphoto interpretation (Cont.)interpretation (Cont.)

Basic characteristics (cont.)Basic characteristics (cont.)• Tone• Texture• Shadows topographic variations geologic

landform• Site: aid in the identification of vegetation

types• Association : e.g. a ferris wheel amusement

park

3.2.2 Photo interpretation strategies3.2.2 Photo interpretation strategies

Direct recognitionDirect recognition• e.g. identification of highway interchange

Inference of site conditions:Inference of site conditions:• e.g. infer the buried gas pipeline light-toned linear

streals• e.g. infer the type of crop crop calendar

Detective Detective put all evidence put all evidence solve a solve a mysterymystery• The interpreter uses the process of convergence of

evidence to successively increase the accuracy and detail of the interpretation

3.2.3 Airphoto interpretation keys3.2.3 Airphoto interpretation keys

Help the interpretation in an organized and Help the interpretation in an organized and consistent manner.consistent manner.

Two basic partsTwo basic parts• A collection of annotated or captioned stereograms• A graphic or word descrioption

Two general typesTwo general types• Selective key• Elimination key more positive answer but may

result in erroneous answers.Dichotomous key (Fig 3.1)

3.2.3 Airphoto interpretation keys 3.2.3 Airphoto interpretation keys (cont.)(cont.)

More easily constructed and more More easily constructed and more reliably utilized for cultural feature reliably utilized for cultural feature identification than for vegetation or identification than for vegetation or landform identificationlandform identification• Crop , tree identification region-by-region,

season-by-season.

3.2.4 Film-filter combinations3.2.4 Film-filter combinations

Affect the amount of information that Affect the amount of information that can be interpreted from the imagecan be interpreted from the image

3.2.5 Temporal aspects of photo 3.2.5 Temporal aspects of photo interpretationinterpretation

Vegetative growth, soil moisture Vegetative growth, soil moisture vary during the yearvary during the year

Observe several time Observe several time better resultbetter result

3.2.6 Photo scale3.2.6 Photo scale

Table 3.1: typical scales and areas of Table 3.1: typical scales and areas of coveragecoverage

Small~1:50,000~medium~1:12,000~largeSmall~1:50,000~medium~1:12,000~large• Small reconnaissance mapping, large area resource

assessment, general resource management planning• Medium identification, classification, mapping of

tree species, agricultural crop type, vegetation community and soil type

• Large intensive monitoring of the damage caused by plant disease, insects or tree blowdown, emergency response to hazardous waste sills and for the intensive site analysis of hazardous waste sites.

3.2.6 Photo scale (cont.)3.2.6 Photo scale (cont.)

NHAP I:NHAP I:• 1980~1985, 1:58,000, 1:80,000, 13200m, leaf-off

NHAP II:NHAP II:• 1985~1987 , leaf-on.

NAPP:NAPP:• 1:40,000, leaf-on, -off

3.2.7 Approaching the interpretation 3.2.7 Approaching the interpretation processprocess

Photographic materials, interpretation Photographic materials, interpretation equipment, goals of the interpretation equipment, goals of the interpretation no no single right way to do.single right way to do.

Examples of requirementExamples of requirement• Identify and count• Identify anomalous conditions• Delineate discrete areal units

Classification system or criteria separate categoriesMinimum mapping unit (MMU) (Fig 3.2)From higher contrast one to lower oneFrom the general to the specificdelineate photographic regions. (tone, texture….)

3.2.8 photo preparation and viewing3.2.8 photo preparation and viewing

Important factors:Important factors:• Relevant collateral sources of information

(maps, field reports, ….)

• Good lighting & access to equipment

• Systematically labeled and indexed

• Boundary delineations

• Fiducial marles, road intersections registration

3.2.8 photo preparation and viewing 3.2.8 photo preparation and viewing (cont.)(cont.)

Effective areas:Effective areas:• Definition: central, bounded by lines bisecting the

area of overlap with every adjacent photograph• Advantages

Cover entire photo without duplicate effort.The least relief displacement

• Construction transfer points• Disadvantages of lelineating effective areas on each

photos need twice efforts• Sometimes, only for every other photo

3.3 Basic photo interpretation 3.3 Basic photo interpretation equipmentequipment

3 purposes3 purposes• Viewing

• Making measurements

• Transfer interpreted information to base maps or digital databases

3.3 Basic photo interpretation 3.3 Basic photo interpretation equipment (cont.)equipment (cont.)

Binocular vision Binocular vision stereoscopic view stereoscopic view 3-D view3-D view• Stereopairs, stereograms• Simple lens stereoscope (Fig 3.3)• Test stereoscopic vision (Fig 3.4) (Table 3.2)

elevation• One-weak eyesight

Cannot get stereoscopic viewBut still can be a good interpreter monocular view

• Viewing the stereogram without a stereoscope


Lens stereoscopesLens stereoscopes• Fig 3.3

• Pros: portable, cheap

Cons: cannot view the entire photo

• Lens spacing: 45~75mm

• Lens magnification: typically 2 power


Mirror stereoscopesMirror stereoscopes• Fig 3.5

• Pros: broader view, a pair of 240 mm photos, measurable.

Cons: large and costly

• Magnification: 2~4 power


Scanning mirror stereoscopeScanning mirror stereoscope• Fig 3.6• Built-in provision• Magnification: 1.5~4.5 power

Zoom stereoscopeZoom stereoscope• Fig 3.7• Continuously variable magnication of 2.5~10(5~20)

power.• Image in each eyepiece rotate 3600

• Expensive, precision, high resolution


Light table:Light table:• Fig 3.8• For transparency• Balance the spectral characteristics of the film and

lamps for optimum viewing conditionColor temperature 3500k black body heat at 3500kNoon daylight~5500kIndoor tungsten bulb 3200k

Distance measurementDistance measurement• Low accuracy cheaper

e.g. a triangular engineer’s scale or metric scale


Area measurementArea measurement• Extremely accurate measurement

see §4.9, §4.10

• Direct measurementError sources measuring device, relief, tilt better to

use vertical photos with low relief.Dot grid (Fig 3.9)Polar planimeter (Fig 3.10)Electronic coordinate digitizer (Fig 3.11)

2

1 area photo area Ground

avgS


Interpretation information mapInterpretation information map• Different size (map and photo)

• Zoom Transfer Scope (Fig 3.13)

• Color additive viewer (Fig 2.42)

3.4 Land use/ land cover mapping3.4 Land use/ land cover mapping

Land cover:Land cover:• The type of feature present on the surface of

the earth

Land use:Land use:• Human activity or economic function

associated with a specific piece of land.

A knowledge of both land use and land A knowledge of both land use and land cover can be important for land cover can be important for land planning and land managementplanning and land management

3.4 Land use/ land cover mapping 3.4 Land use/ land cover mapping (cont.)(cont.)

USGS land use and land cover USGS land use and land cover classification systemclassification system• Land use and land cover should not be

intermixed , but practically, land cover land use

• but also need some additional information sources

• Use categories rather than specific information


USGS land use and land cover USGS land use and land cover classification system (cont.)classification system (cont.)• Designed criteria:

1)85% accuracy

2)Same accuracy for the several categories

3)Repeatable from one time of sensing to another

4)Applicable over extensive areas

5)Infer land use


USGS land use and land cover USGS land use and land cover classification system (cont.)classification system (cont.)• Designed criteria (cont.)

6)Use for different time of a year

7)Divisible categories

8)Aggregation of categories

9)Comparison with future data

10)Recognize multiple uses of land


USGS land use and land cover classification USGS land use and land cover classification system (cont.)system (cont.)• Table 3.3: level I, II• Also provide level III IV, but it is intended to let the

local users to design level III, IV. (Fig 3.14)• Reviewing and revising more wetland classes• Table 3.4: Representative image interpretation

formats for various classification levels.• General relationship, not restriction.• Minimum size of land use/land cover units mapped at

various classification levels.The smallest representative area on a map 2.5mm x 2.5mm.


Level I classesLevel I classes• Urban or built-up land take precedence

• Agricultural land drained wet lands for agriculture

• Rangeland

• Forest land tree-crown areal density>10%If has wet land characteristics wet land category

• Water


Level I classes (cont.)Level I classes (cont.)• Wetland

Shallow water with submerged vegetation water classShort-lived wetness or flooding wetlandCultivated wetlands agricultural landUncultivated wetland wetlandDrained wetland for other purposes other classes

• Barren land: vegetation or other cover <1/3• Tundra: treeless regions beyond the geographic limit

of the boreal forest and above the altitudinal limit of trees in high mountain ranges.

• Perennial snow or ice areas


USGS land use/land cover classification USGS land use/land cover classification system mapssystem maps• 1:250,000

• For most categories: a minimum map unit 16 ha

• Some 1:100,000

• Digital data:vector formatraster format (grid cell size 4 ha)

3.5 Geologic and soil mapping3.5 Geologic and soil mapping

Complex and variable earth surfaceComplex and variable earth surface• Topographic relief and material composition

• Reflect the bedrock, unconsolidated materials, agents of charge.

Rock type, fracture, effects of internal Rock type, fracture, effects of internal movement, erosion,movement, erosion,• Bear the imprint of the processes that

produced them

3.5 Geologic and soil mapping (cont.)3.5 Geologic and soil mapping (cont.)

Geomorphological principlesGeomorphological principles• Airphoto interpretation & geological and soil

mapping• Identify and evaluate materials and structures.

Geological mappingGeological mapping• History of development: 1913, 1920, 1940…..• Identify landforms, rock types, rock structure,

portray geological units and structure and spatial relationship.

• explore mineral resource.Far below the surface and inaccessible regionR.S. potential area drill holes


Geological mapping (cont.)Geological mapping (cont.)• Multistage image interpretation:

1:250,000, 1:100,000 1:58,000~1:130,000 1:20,000

• Lineaments: regional linear features linear alignment of regional morphological features streams, escarpments, mountain ranges, tonal features (fractures or fault zones).Scales: a few ~ hundreds of kmImportant in mineral resource studies ore depositionDetection angular relationship. (Fig 3.16)


Geological mapping (cont.)Geological mapping (cont.)• Ronchi grid

A diffraction grate: 78 lines/cm|| grid suppressed grid enhanced.

• Lithologic mappingThe mapping of rock unitsStereoscopic viewing enhanceSee § 3.15


Geological mapping (cont.)Geological mapping (cont.)• Geobotany

The relationship between a plant’s nutrient requirements and 2 interrelated factors– the availability of nutrients in the soil and the physical properties of the soil, including the availability of soil moisture indirect indicator

Distribution of vegetation (indirect indicator) composition of the underlying soil and rock materialsGeobotanical approach to geologic mapping

Cooperative effort among geologists, soil scientists and field-oriented botanists

Identification of vegetation anomalies related to mineralized areas.


Geological mapping (cont.)Geological mapping (cont.)• Geobotany (cont.)

Geobotanical anomalies:1. Anomalous distribution of species and/or plant communities2. Sturted growth and/or decreased ground cover3. Alteration of leaf pigment and/or physiographic process that produce leaf color

changes.4. Anomalous charges in the phenologic cycle. e.g. early foliage change senescence in the fall. alteration of flowering periods, late leaf flush

Taking photos several times during the year. Establishing “normal” condition identify “anomalous”Band 1.6 um & 2.2 um are important for mineral

exploration and lithologic mapping.


Soil mappingSoil mapping• Soil survey resource information land use

planning

• Trained scientists + extensive field works + airphoto interpretation identify soil & delineate soil boundaries.

• Airphoto interpretation 1930s Panchromatic aerial photos: 1:15,840~1:40,000


Soil mapping (cont.)Soil mapping (cont.)• Agricultural soil survey (Fig 3.17, Table 3.6)

USDA, 1900s.1957 publish1980s many counties line maps or digital formPurposes:

Estimating crops Evaluating rangeland suitability Determine woodland productivity Assessing wildlife habitat conditions Judging suitability for various recreational uses Judging suitability for various development uses


Soil mapping (cont.)Soil mapping (cont.)• The reflection of sunlight from bare soil

surfacesSoil moisture contentSoil textureSurface roughnessIron oxideOrganic matter content


Soil mapping (cont.)Soil mapping (cont.)• Plate 8: different appearance of one field

during one growing seasonSoil parent materials glacial meltwater deposits of

stratified sand and gravel overlain by 45~150 cm of loess (wind-deposited silt)

(a), (b), (c): corn plants 10 cm 2.5 cm rain fall uniform patchiness dry high infiltration & slight mound wet low infiltration & receive runs off


Soil mapping (cont.)Soil mapping (cont.)• Plate 8: (cont.)

(d), (e), (f): corn plants 2m little rain fall dry leaves and stalks drying out and turn brown. wet continuing to grow and still green

Soil scientist four classes. (Fig 3.18 & Table 3.7)

• Certain times of the year are better suited to aerial photography for soil mapping purposes than others.

3.6 Agricultural applications3.6 Agricultural applications

Big picture direct applicationBig picture direct application Crop type classification (and area Crop type classification (and area

inventory)inventory)• Spectral response and photo texture

identify crop type• Require a knowledge of the developmental stages of

each crop in the area to be inventoried crop calendar

• Use photographs taken on several dates during the growing cycle for crop identification

• Color + infrared films are better than panchromatic film

3.6 Agricultural applications (cont.)3.6 Agricultural applications (cont.)

Crop type classification (cont.)Crop type classification (cont.)• Stereoscopic coverage

plant height discrimination

• Table 3.8: dichotomous airphoto interpretation key use single-date panchromatic photography only broad classes of crops are to be inventories.

• Fig 3.19: demonstrate the importance of date of photography, photo tone and texture, and stereoscopic coverage.


Crop condition assessmentCrop condition assessment• Large scale airphotos documenting deleterious conditions crop disease, insect damage, plant stress, disaster damage.

• Table 3.9: typical crop management information potentially obtainable from large scale color infrared aerial photographs.


Crop condition assessment (cont.)Crop condition assessment (cont.)• Detailed within field interpretations of soil and crop

condition fertilizer spreaders and irrigators crop management activities fn(geolocation)

• Detected plant diseases• detected insect damage• other detected damage:• A difficult task finer differences in spectral

response


Crop yield estimationCrop yield estimation• Simple & straightforward

area * yield/area yield• Complex soil moisture, soil fertility, air and soil

temperature, disease, insect stress,…..• Crop yield prediction climatic & meteorological

conditions.• Traditional approach: area * yield/area (airphoto interpretation) (field inspection)• Direct approach historical information deviation


Other applicationsOther applications• Determine areas erosion control, weed

control fertilizing, replanting, fencing or other remedial measures

• Taxation & real estate purposes

• Assessment of irrigation systems

• Farm livestock surveys

3.7 Forestry applications3.7 Forestry applications

1/3 of the world’s land area1/3 of the world’s land area Tree species identificationTree species identification

• More complex than crop identification.Complex mixture more uniformForest understory

• Step 1: eliminationStep 2: establish groupsStep 3: identify individual species

• Shape & size Fig 3.20: Silhouettes of forest treesFig 3.21: Aerial views of tree crowns.

• Pattern & Shadows

3.7 Forestry applications (cont.)3.7 Forestry applications (cont.)

Tree species identification (cont.)Tree species identification (cont.)• Tone relative tones• Texture tufted, smooth, billowy• Fig 3.22, Fig 3.23

Black spruce coniferous, slender crowns, pointed tops. even height or change gradually carpetlike appearance

Aspen deciduous, rounded crowns widely spaced, variable in size and density

Balsam fir symmetrical coniferous, sharply pointed tops thicker than black spruce erratic changes in size uneven and irregular pattern


Tree species identification (cont.)Tree species identification (cont.)• Fig 3.22, Fig 3.23 (cont.)

Fig 3.22: Black spruce AspenFig 3.23: Balsam fir Black spruce (mixture)Art

• Scale does matter• Table 3.10, 3.11

Airphoto interpretation key• Phenological correlations

Changes in the appearance in the different seasons of the yeare.g. separation of deciduous and evergreen treese.g. difference in the time at which species leaf out


Timber cruisingTimber cruising• Objective: determine the volume of timber that might

be harvested from an individual tree of a stand of trees

• To be successful skilled interpreter + aerial and ground data

• Photo measurements1. Tree height or stand height measuring relief displacement or image

parallax.

2. Tree-crown diameter distance measurements

3. Density of stocking

4. Stand area


Timber cruising (cont.)Timber cruising (cont.)• Photo volume tables

Multiple regression (extracted data, ground data)Volume of individual trees = fn(species, crown diameter,

height)(Table 3.12)

For large scale photos, scattered trees in open areas.Table 3.13: stand volume table


Assessment of disease and insect Assessment of disease and insect infestationsinfestations• Panchromatic photos often used

Medium and large scale color and color infrared photos most successful surveys

• Tree disease• Insect damage• Forest damage• Plate 9: gypsy moth defoliation of hardwood

trees.


Additional applications:Additional applications: Success Success high quality reference datahigh quality reference data

3.8 Rangeland applications3.8 Rangeland applications

Definition: see Definition: see § § 2.42.4 Provide forage, support land use Provide forage, support land use

(agriculture, recreation housing)(agriculture, recreation housing) Range managers use air photos in Range managers use air photos in

much the same way as do foresters.much the same way as do foresters.• Main concern: vegetation change over time

• Forage yield estimation.

3.9 Water resource applications3.9 Water resource applications

Water resources: irrigation, power Water resources: irrigation, power generation, manufacturing, recreation, generation, manufacturing, recreation, ……

Airphoto Airphoto monitor monitor quality, quantity, quality, quantity, distributiondistribution

Interaction of sunlight and waterInteraction of sunlight and water• Absorption=fn()

near-infrared a few tenths of a meter dark tone0.48~0.6um best penetration (15~20m)

underwater hazered few meters

3.9 Water resource applications 3.9 Water resource applications (cont.)(cont.)

Analysis of underwater featuresAnalysis of underwater features• White sand bottoms

normal color film blue-greencolor infrared (yellow filter) blue

• Fig 3.24: color and color infrared photos for Hanauma Bay

3.9 Water resource applications 3.9 Water resource applications (cont.)(cont.)

Water pollution detectionWater pollution detection• Polluted water impurities limit its use

• Natural sources of pollution:e.g. minerals leached from soil and decaying vegetation

• Point source:e.g. industrial outfalls

• Non-point source:e.g. fertilizer and sediment runoff.

3.9 Water resource applications3.9 Water resource applications(cont.)(cont.)

Water pollution detection (cont.)Water pollution detection (cont.)• Materials (excessive amounts) water

pollution1.Organic wastes

2.Infections agents

3.Plant nutrients

4.Synthetic-organic chemicals

5.Inorganic chemical and mineral substances

6.Sediment

7.Radioactive substances

8.temperature


Water pollution detection (cont.)Water pollution detection (cont.)• Air photo

type and concentration? discharge point & dispersionin some instances it is possible to make valid observations about

sediment concentrations using quantitative photographic radiometry coupled with the laboratory analysis of selective water samples.

• Fig 3.25: dispersal plume of silt-laden water flowing into a lake

• Air photos enforcement of antipollution law• Oil film on water (Fig 3.26)

Oil slicksOil sheensOil rainbows


Lake eutrophication assessmentLake eutrophication assessment• Trophic state

Eutrophic state (nutrient rich)Oligotrophic (low nutrient, high Oxygen)

• Eutrophication: the general process by which lakes age

• Different people different levels of eutrophication that can be accepted

• Air-photo mapping aquatic macrophytesTable 3.14: interpretation key

• Algae concentration good indicator of a lake’s trophic status


Flood damage estimationFlood damage estimation• Fig 3.27: multi-date sequence and aftereffects.

A. normal appearanceB. peak of a flood.C. 3 weeks after floodingD. 6 weeks after floodingCrop damageStreaked pattern of light-toned lines direction of flood flow.

• Fig 3.28:For flood damage assessmentB is clean than a Refer to Fig 6.12b for satellite image


Other ApplicationsOther Applications• Vegetation index

Ground water location Groundwater discharge areas wellGroundwater recharge zone protect

• Hydrologic watershed assessmentReservoir site selectionShoreline erosion studiesSnow cover mappingSurvey of recreational use of lakes and rivers

3.10 Urban and regional planning 3.10 Urban and regional planning applicationsapplications

Timely, accurate and cost-effective sources Timely, accurate and cost-effective sources of data (requirement)of data (requirement)

Population estimates.Population estimates.• Air-photo dwelling units of housing type

Housing quality studiesHousing quality studies• Statistical analysis of a set of environmental quality

factors. e.g. house size, lot size,…

Traffic and parking studiesTraffic and parking studies• Traditional on-the-ground vehicle count• Air-photo shows distribution area of congestion

3.10 Urban and regional planning 3.10 Urban and regional planning applications (cont.)applications (cont.)

Various factors: RS photo Various factors: RS photo data data GIS AnalysisGIS Analysis• Transportation route location

• Sanitary landfill site selection

• Power plant sitting

• Transmission line location

Fig 3.29: urban change detectionFig 3.29: urban change detection

3.11 Wetland mapping3.11 Wetland mapping

Significance of wetlandSignificance of wetland• Retain water

• Reduce flood level

• Trap suspended solids and attached nutrients clear lake

• For wildlife (drinking and stopping)

• Species diversity and food web.

• Biological record

• recreation

3.11 Wetland mapping (cont.)3.11 Wetland mapping (cont.)

Purpose (multi-or single-) Purpose (multi-or single-) inventoryinventory 3 basic elements for identifying wetland3 basic elements for identifying wetland

• Hydrophytic vegetation• Hydric soils• Wetland hydrology

Fig 3.30 color infrared photo for wetland Fig 3.30 color infrared photo for wetland mappingmapping

Fig 3.31. Wetland vegetation mapFig 3.31. Wetland vegetation map Table 3.15 airphoto interpretation key.Table 3.15 airphoto interpretation key.

3.12 wildlife ecology applications3.12 wildlife ecology applications

WildlifeWildlife

Wildlife ecologyWildlife ecology

Wildlife conservationWildlife conservation

Wildlife managementWildlife management

3.12 wildlife ecology applications 3.12 wildlife ecology applications (cont.)(cont.)

Wildlife habitatWildlife habitat• Combination of climate, substrate and vegetation• Niche• All mapping techniques are applicable• “edges” delineation• GIS• Fig 3.32: Wildlife habitat types in Sheboygan Marsh

9 vegetation classes 5 wildlife habitat typesMuskrat hut in AV area, 100 white spots


Wildlife censusingWildlife censusing• Ground survey + aerial visual observation• Problems of counting

Quick decision?Aggregation?Low-flying aircraft disturb

• Best method: vertical aerial photographyAccurate countingNormal patterns of spatial distributionPermanent recordProlonged study more informationOnly valid for those open areas during daytime


Wildlife censusingWildlife censusing• Scale=fn(animal size)

• Film-filter high contrast (Fig 2.18)

• Digitize computer-aid counting

• Fig 3.33: Prairie dog colony

• Fig 3.34: Beluga whalesCalveNumber & lengthBachelor group

3.13 Archaeological application3.13 Archaeological application

Airphotos Airphotos locate sites whose existence has locate sites whose existence has been lost to historybeen lost to history• Both surface and subsurface features

Surface features:Surface features:• Visible ruins: e.g. Stonehenge, castles, Indian dwelling.• Mounds: e.g. bird-shaped and serpent-shaped Indian

mounds.• Rock structures e.g. Bighorn Medicine Wheel, mounds• Fig 3.35: Nazca lines

3.13 Archaeological application 3.13 Archaeological application (cont.)(cont.)

Subsurface features:Subsurface features:• e.g. buried ruins of buildings, ditches, canals, roads• Tonal anomalies in soil moisture, crop growth,

ephemeral difference in frost patterns• Fig 3.36: ancient city of Spina

A city of canals and waterways.Dark-toned linear feature dense vegetation wet location former

canalsLight-toned rectangular areas sparse vegetation over sand brick

foundationLight-toned linear feature present-day drainage ditches.

3.13 Archaeological application 3.13 Archaeological application (cont.)(cont.)

Subsurface features:Subsurface features:• Fertile loess soils over the white chalk bedrock

(foundation)Fig 3.37: deep winter plowing scraped the foundation

brought up chalkFig 3.38:

recent conversion from pasture to cropland few fertilizer over the foundation light toned.

3.14 Environmental assessment3.14 Environmental assessment

Human activities Human activities adverse adverse environmental effects.environmental effects.

U.S. NEPA (1969)U.S. NEPA (1969)• Environment impact statements• Key items

1.Environmental impact2.Cannot-avoided impact3.Alternatives4.Relationship(short-& long-term)5.Irreversible and irretrievable commitments

3.14 Environmental assessment 3.14 Environmental assessment (cont.)(cont.)

Principal biophysical effects of human Principal biophysical effects of human activity on environmentactivity on environment1.Change natural drainage conditions

2.Change water turbidity & temperature

3.Chemical pollutants

4.Change in vegetation

5.Change wildlife population and distribution

US. RCRAUS. RCRA

3.14 Environmental assessment 3.14 Environmental assessment (cont.)(cont.)

AirphotosAirphotos EPA’s principal remote sensing tools

e.g.: emergeray response photography to the spillage of hazard materials

e.g.: site analyses of waste sites Historical photos Drainage conditions

e.g.: site analyses of waste sites Historical photos Drainage conditions

e.g.: locate potential sites for drilling and sampling of hazardous wastes

e.g.: identification of failing septic systems

3.15 Principles of landform 3.15 Principles of landform identification and evaluationidentification and evaluation

Significance of terrain characteristicsSignificance of terrain characteristics Airphotos Airphotos

• Bedrock type• Landform• Soil texture• Site drainage conditions• Susceptibility to flooding• Depth of unconsolidated materials over bedrock• Slope of land surface.

3.15 principles of landform 3.15 principles of landform identification and evaluation (cont.)identification and evaluation (cont.)

Soil characteristicsSoil characteristics• Definition:

e.g. 10m deposit (C)= 9m unaltered (B) + 1m weathered (A)Engineering: A+B+CSoil science (pedological): A+B

• Soil horizonA horizon: surface soil topsoil

0~60cm, 15~30cm Weathered horizon Most organic matter

B horizon: subsoil 0~250cm, 45~60cm Fire-textured particles from A horizon

C horizon: parent material


Soil characteristics (cont.)Soil characteristics (cont.)• Three origins of soil materials

Residual soilsTransported soilsOrganic soils

• Table 3.16: soil particle size designations.Silt+clay 50%=fine textureSand+gravel> 50%= coarse texture

• For residual soil: texture B+CFor transported soil: texture parent material

• USDA soil drainage classes (7 classes) natural • Artificial drainage


Land use suitability evaluationLand use suitability evaluation• Topographic characteristics

For subdivision development: 2~6% Steep enough for good surface drainage Flat enough no site development problems

0~2% may have some drainage problems6~12% more interesting but more costly>12% problem in street and lot design, as well as domestic sewage

disposal>20% severe limitationFor industrial park and commercial site < 5 %

• Soil texture and drainage conditionsWell-drained+coarse texture soils few limitation


Land use suitability evaluation (cont.)Land use suitability evaluation (cont.)• Groundwater tables

Shallow problems in septic tankAt least 2m

• Depth of bedrockPrefer > 2m1~2m may be feasible in some cases

• Soil-slope conditionSlope stability analysis not discussedIncipient landslide failure detectable using airphoto


Elements of airphoto interpretation for Elements of airphoto interpretation for landform identification and evaluationlandform identification and evaluation• Topography

A distinct topographic change at the boundary between two different landforms.

• Drainage pattern and textureIndicators of landform, bedrock, soil, drainage conditionsFig 3.39: six basic drainage patterns destruct ional from erosion

1. Dendritic2. Rectangular3. Trellis4. Radial5. Cantripetal6. Deranged


Elements of airphoto interpretation (cont.)Elements of airphoto interpretation (cont.)• Drainage pattern and texture (cont.)

Fig 3.401. Coarse-texturedgood internal drainage

2. Fine-texturedpoor internal drainage

• ErosionGullies:

The smallest drainage feature from airphotos A meta wide and a hundred meters long Formation rainfallnot percolate rivuletsrunoffenlarge Fig3.41

1. V-shape: sand & gravel

2. U-shape: silty soils

3. Long with gently rounded: silty clay, clay


Elements of airphoto interpretation Elements of airphoto interpretation (cont.)(cont.)• Photo tone

BrightnessUse relative tone valuesFig 3.54

Lighter tone higher position Varying soil moisture content different sunlight reflection mottled tonal

pattern

Capillary action tonal gradients boundary sharpnessColor or color infrared same principle


Elements of airphoto interpretation (cont.) Elements of airphoto interpretation (cont.) • Vegetation and land use

Indicator, but in many cases, they are obscured

The airphoto interpretation processThe airphoto interpretation process• Initially consider all elements• After some experience subconsciously +

instantaneously• Humid climates >50 cm rainfall per year

Arid climates <50 cm rainfall per year• Airphoto interpretation field operation

Verifysuggestion

3.16 Bedrock landforms3.16 Bedrock landforms

Horizontally bedded sandstoneHorizontally bedded sandstone• Airphoto identification

Topography:Drainage and erosion:Photo toneVegetation and land use

• Fig 3.43

3.16 Bedrock landforms (cont.)3.16 Bedrock landforms (cont.)

Horizontally bedded shaleHorizontally bedded shale• Airphoto identification


• Fig 3.44


Horizontally bedded limestoneHorizontally bedded limestone• Airphoto identification


• Fig 3.45


Horizontally bedded granitic rocksHorizontally bedded granitic rocks• Airphoto identification


• Fig 3.46


Horizontally bedded lava flowsHorizontally bedded lava flows• Airphoto identification


• Fig 3.47

3.17 Aeolian landforms3.17 Aeolian landforms

Sand dunesSand dunes• Formation

• Fig 3.48

3.17 Aeolian landforms (cont.)3.17 Aeolian landforms (cont.)

Sand dunes (cont.)Sand dunes (cont.)• Airphoto identification


• Fig 3.49

3.17 Aeolian landforms (cont.)3.17 Aeolian landforms (cont.)

LoessLoess• Airphoto identification


• Fig 3.51

3.18 Glacial landforms3.18 Glacial landforms

Formation:Formation:• Repeated advances of glacial ice over 30%

• Glaciation forms:Valley glaciationContinental glaciation

• Ice move abrade and pluck

• Glacial driftMaterials deposite by glaciation

3.18 Glacial landforms (cont.)3.18 Glacial landforms (cont.)

Till landformsTill landforms• Repeated advances of glacial ice over 30%

• Glaciation forms:Valley glaciationContinental glaciation

• Ice move abrade and pluck

• Glacial driftMaterials deposite by glaciation


End morainesEnd moraines• Airphoto identification


• Fig 3.53


Basal ground moraine areaBasal ground moraine area• Airphoto identification


• Fig 3.54


DrumlinsDrumlins• Airphoto identification


• Fig 3.55


EskersEskers• Airphoto identification


• Fig 3.56


Outwash sedimentsOutwash sediments• Airphoto identification


• Fig 3.57


Glacial lakebedsGlacial lakebeds• Airphoto identification


• Fig 3.58


Beach ridgesBeach ridges• Airphoto identification


• Fig 3.59

3.19 Fluvial landforms3.19 Fluvial landforms

Formation:Formation:• Flowing water erosion + transportation +

deposition

• fn(water velocity, particle size)Stream competence: the maximum-size particles a stream

can transport at a given velocityStream capacity: the maximum amount of materials the

stream can transport and is related to stream volume

3.19 Fluvial landforms (cont.)3.19 Fluvial landforms (cont.)

Alluvial fansAlluvial fans• Airphoto identification

Topography: fan shapeDrainage and erosion:

excellent internal drainage limited surface drainage with few gullies Numerous distributary channels

Photo tone Generally light, but distributary channels may be darker

Vegetation and land use Lack of vegetation May be heavier vegetation at base


Alluvial fans (cont.)Alluvial fans (cont.)• Fig 3.60

Slope: apex (10%) valley (12%) base (8%)Darker tone and vegetation near the base of fan


FloodplainFloodplain• Airphoto identification

Topography: Generally level with small downstream gradient Natural levees slightly higher position Slack water deposits in lowest position

Drainage and erosion: Principal stream flow Wide floodplain second stream High groundwater table

Photo tone Point bar deposits, natural levee light tone Slack water deposits darker tone Oxbow uniform gray tone

Vegetation and land use Often agricultural use


Alluvial fans (cont.)Alluvial fans (cont.)• Fig 3.61

Present channel (PC)Abandoned channel (AC)Point bar deposits (PB)Oxbow lake (OX)Slack water deposit (SW)


DeltaDelta• Type

Arcuate delta: e.g. the Nile DeltaBirdfoot delta: e.g. the Mississippi Delta

• Fig 6.13

3.20 Organic soils3.20 Organic soils

Formation:Formation:• Continuous water saturation limit the

circulation of O2 decomposition of organic matter accumulation organic matter > mineralization muck or peat

CharacteristicsCharacteristics• Typically begins in lakes or ponds• Poor foundations for construction activities• If over drain irreversible hardening• If too dry fire hazard

3.20 Organic soils (cont.)3.20 Organic soils (cont.)

Airphoto identificationAirphoto identification• Found

Topographic depressions (moraine, ground moraine, floodplain, oxbows)

Depression between sand dunes, beach ridgesLimestone sinkholeKettle hole

• TopographyVery flat, often sharp contrast with surrounding material


Airphoto identification (cont.)Airphoto identification (cont.)• Drainage and erosion

Poorly drain, few gulliesFarm artificially drain

• Photo tone, vegetation and land useBare soil dark toneDrained agricultural areas distinctive pattern


Fig 3.62Fig 3.62• Organic soils

• Glacial till, drumlin

• Well drained, cultivated

• 2m ~ 5m Fibrous peat in a former glacial lakebed

• 80~95% organic matter, 5~20% mineral matter

Documents

Chapter 3 Introduction to airphoto interpretation Introduction to Remote Sensing Instructor: Dr. Cheng-Chien LiuCheng-Chien Liu Department of Earth Science