PhotogrammetryPhotogrammetry

►photo = "picture“,photo = "picture“,

► grammetry = "measurement“, grammetry = "measurement“, therefore photogrammetry = “photo-therefore photogrammetry = “photo-

measurement”measurement”

Lecture outlineLecture outline►DefinitionDefinition►Principle of photogrammetry.Principle of photogrammetry.►Uses.Uses.►Aerial cameraAerial camera►Aerial photograph.Aerial photograph.►Scale of vertical and tilted photographScale of vertical and tilted photograph►Ground coordinatesGround coordinates►Procedure of aerial survey.Procedure of aerial survey.►Photomaps and mosaicsPhotomaps and mosaics►StereoscopesStereoscopes

IntroductionIntroduction

►Definition of Photogrammetry:Definition of Photogrammetry: the art, the art, science, and technology of obtaining science, and technology of obtaining information about physical objects and information about physical objects and the environment by photographic and the environment by photographic and electromagnetic images.electromagnetic images.

Basic InformationBasic Information

►Mapping from aerial photos is the best Mapping from aerial photos is the best mapping procedure yet developed for mapping procedure yet developed for most large projects.most large projects. Used successfully for maps varying in scale Used successfully for maps varying in scale

from 1:1,000,000 1:120 with contour from 1:1,000,000 1:120 with contour intervals as small as 1 foot.intervals as small as 1 foot.

Topographic mapping is the most common Topographic mapping is the most common form. – U.S.G.S updated and done this way.form. – U.S.G.S updated and done this way.

Used to reconstruct a scaled 3-dimensional Used to reconstruct a scaled 3-dimensional optical model of the lands surface using a optical model of the lands surface using a stereoplotterstereoplotter..

Basic InformationBasic Information

►Uses: Aerial photosUses: Aerial photos Aid: geological investigations, soil Aid: geological investigations, soil

surveys, land surveys, tax mapping, surveys, land surveys, tax mapping, reconnaissance and military intelligence, reconnaissance and military intelligence, urban and regional development, urban and regional development, transportation system investigations, transportation system investigations, quantity estimates, shore erosion, etc.quantity estimates, shore erosion, etc.

Mathematical methods have been Mathematical methods have been developed to make precise 3-dimensional developed to make precise 3-dimensional measurements from photos.measurements from photos.►Phototriangulation: 3-dimensional positioning Phototriangulation: 3-dimensional positioning

of survey stations.of survey stations.

Basic Information ContinuedBasic Information Continued

Photo has been used to take geometric Photo has been used to take geometric measurements of human bodies, artificial measurements of human bodies, artificial human hearts, large radio telescopes, human hearts, large radio telescopes, ships, dams, buildings and very accurate ships, dams, buildings and very accurate reproductions.reproductions.

► In general it is not economical for In general it is not economical for small projects – the cost break even small projects – the cost break even point is somewhere between 30 – 100 point is somewhere between 30 – 100 acres depending on the situation.acres depending on the situation.

Basic InformationBasic Information

►Photogrammetry can not be used Photogrammetry can not be used successfully over the following types successfully over the following types of terrain.of terrain. Desert or plains areas, sandy beaches, Desert or plains areas, sandy beaches,

and snow – the photograph as uniform and snow – the photograph as uniform shades with little texture.shades with little texture.

Deep canyons or high buildings that Deep canyons or high buildings that conceal ground surface.conceal ground surface.

Areas covered by dense forest.Areas covered by dense forest.

2 Basic Categories 2 Basic Categories

►Photogrammetry -Photogrammetry - Known as Aerial Known as Aerial surveysurvey

►Classification of photogrammety Classification of photogrammety

Photogrammetry for Photogrammetry for EngineeringEngineering

►Defined: Photogrammetry is the Defined: Photogrammetry is the process of measuring images on a process of measuring images on a photograph.photograph.

►Modern photogrammetry also uses Modern photogrammetry also uses radar imaging, radiant radar imaging, radiant electromagnetic energy detection and electromagnetic energy detection and x-ray imaging – called x-ray imaging – called remote sensingremote sensing..

Aerial cameraAerial camera

Types of Aerial PhotographsTypes of Aerial Photographs

Principle of Aerial surveyPrinciple of Aerial survey

Definitions Definitions (GTU:Nov/Dec-(GTU:Nov/Dec-2011)2011)

► Exposure station (o) : Exposure station (o) : The point in the atmosphere The point in the atmosphere occupied by center of camera lenses at instance of occupied by center of camera lenses at instance of photography.photography.

► Flying height Flying height : Vertical distance between exposure : Vertical distance between exposure station and mean sea level.station and mean sea level.

► Flight line: Flight line: Line traced by exposure station in Line traced by exposure station in atmosphere ( track of aircraft)atmosphere ( track of aircraft)

► Photo principal plane (k) Photo principal plane (k) It is point on photograph It is point on photograph obtained by projecting camera axis to intersect at obtained by projecting camera axis to intersect at a point on photograph known as photo principal a point on photograph known as photo principal pointpoint(k)(k)

► Camera axis extended up to ground, the point Camera axis extended up to ground, the point obtained on ground is called obtained on ground is called Ground Principal point Ground Principal point (K) (K)

DefinitionsDefinitions► Photo nadir point (n) : Photo nadir point (n) : It is a point on It is a point on

photograph obtained by dropping vertical line photograph obtained by dropping vertical line from camera center. That plumb line extendd from camera center. That plumb line extendd up to ground gives Ground Nadir Point (N)up to ground gives Ground Nadir Point (N)

► Horizon point (h) : Horizon point (h) : It is point of intersection of It is point of intersection of horizontal line through center of lenses and horizontal line through center of lenses and principal line (np) on photograph.principal line (np) on photograph.

► Principal planePrincipal plane:- Plane defined by exposure :- Plane defined by exposure station (O), Ground nadir point (N) and ground station (O), Ground nadir point (N) and ground principal point (P) ( i.e. plane NOK) principal point (P) ( i.e. plane NOK)

► Principal line : Line of intersection of principal Principal line : Line of intersection of principal plane with photograph plane -nkplane with photograph plane -nk

DefinitionsDefinitions► Azimuth : (A) : Azimuth : (A) : Clockwise horizontal angle Clockwise horizontal angle

measured about ground nadir point from true measured about ground nadir point from true north to the principal plane of photograph.(north to the principal plane of photograph.(ФФ ) )

► Swing (S) Swing (S) :-Angle measured in plane of :-Angle measured in plane of photograph from +y axis clockwise to photo photograph from +y axis clockwise to photo nadir point.nadir point.

► Isocenter (i) Isocenter (i) :-Point on photo where bisection of :-Point on photo where bisection of tilt falls on photo. ( dotted line ------- in sketch).tilt falls on photo. ( dotted line ------- in sketch).

► Axis of tilt:- Axis of tilt:- It is line in plane of photograph It is line in plane of photograph perpendicular to principal line at the isocenter.perpendicular to principal line at the isocenter.

Scale of PhotographScale of Photograph

SCALE OF PHOTOGRAPHSCALE OF PHOTOGRAPH

►To perform computations, one must To perform computations, one must know:know: H = height above datum from which H = height above datum from which

photos taken.photos taken. f = focal length of camera lens – in cm or f = focal length of camera lens – in cm or

mmmm

Scale of a Vertical Scale of a Vertical PhotographsPhotographs

► S = orS = or

► f = focal length 6” or 152.4 mm is commonf = focal length 6” or 152.4 mm is common►H’ = height of plane above groundH’ = height of plane above ground► h = height (elevation) of groundh = height (elevation) of ground►H = height of place above datumH = height of place above datum

ff

HH’’

ff

H-H-hh

Scale of a Vertical PhotoScale of a Vertical Photo

Scale varies from point to Scale varies from point to pointpoint

►Scale of photograph at point P on Scale of photograph at point P on ground having elevation hground having elevation hp p

►Scale for any point = s Scale for any point = s

►Representative fraction (R.F.) = Representative fraction (R.F.) =

Scale of a Vertical PhotoScale of a Vertical Photo

►Datum Scale Datum Scale = All the points of photograph are = All the points of photograph are asumed to be projected on M.S.L. (R.L.± 0.00)asumed to be projected on M.S.L. (R.L.± 0.00)

SSD D ==

►Average Scale Average Scale = = All the points of photograph All the points of photograph are asumed to be having average elevation are asumed to be having average elevation above m.s.l.above m.s.l.

SSAV.AV. = =

ff

HH

ff

H-H-hhav.av.

Other methods of finding Other methods of finding scale of vertical photographscale of vertical photograph

► By measuring Ground distanceBy measuring Ground distance

► By determining the distance from By determining the distance from existing mapexisting map

► = Photo distance= Photo distance► = distance on existing map = distance on existing map

Relief DisplacementRelief Displacement

► Relief Displacement exists because photos Relief Displacement exists because photos are a perspective projection.are a perspective projection.

► Use this to determine the height of object:Use this to determine the height of object:

h=h=

h = height of objecth = height of object

d = radial distance to top of object-radial d = radial distance to top of object-radial distance to bottom of object.distance to bottom of object.

r = radial distance to top of object.r = radial distance to top of object.

d d (H’)(H’)

rr

Relief displacement Relief displacement ►The scale of an aerial photograph is The scale of an aerial photograph is

partly a function of flying height. partly a function of flying height. ►Thus, variations in elevation cause Thus, variations in elevation cause

variations in scale on aerial variations in scale on aerial photographs. Specifically, the higher photographs. Specifically, the higher the elevation of an object, the farther the elevation of an object, the farther the object will be displaced from its the object will be displaced from its actual position away from the principal actual position away from the principal point of the photograph (the point on point of the photograph (the point on the ground surface that is directly the ground surface that is directly below the camera lens). below the camera lens).

Relief displacement Relief displacement

►The scale of an aerial photograph is The scale of an aerial photograph is partly a function of flying height. partly a function of flying height.

►The lower the elevation of an object, The lower the elevation of an object, the more it will be displaced toward the more it will be displaced toward the the principal pointprincipal point. This effect, called . This effect, called relief displacementrelief displacement, is illustrated in , is illustrated in the diagram below. Note that the the diagram below. Note that the effect increases with distance from the effect increases with distance from the principal point.principal point.

Equation for relief displacement Equation for relief displacement (d) (d)

Displacement and errorsDisplacement and errors

► In photography survey we try to represent In photography survey we try to represent 3-D surface of earth as 2D image.3-D surface of earth as 2D image.

►Object appears in photographs are Object appears in photographs are geometrically distorted. / ( known as relief geometrically distorted. / ( known as relief displacement)displacement)

► Reasons for Distortions Reasons for Distortions Perspective viewPerspective view Movement of cameraMovement of camera Instability of aircraftInstability of aircraft Variation in altitude , tilt and speedVariation in altitude , tilt and speed Curvature of earthCurvature of earth Rotation of EarthRotation of Earth

Ground control surveyGround control survey►Purpose: Determine exact position of Purpose: Determine exact position of

aerial camera at the instant of exposure aerial camera at the instant of exposure and identify the objects on ground.and identify the objects on ground.

►StepsSteps►Targets (signals) are placed on ground.Targets (signals) are placed on ground.►Targets are surveyed by TriangulationTargets are surveyed by Triangulation►Ground control ( Triangulation, B.M. Ground control ( Triangulation, B.M.

Azimuth,)and photo control ( position of Azimuth,)and photo control ( position of signal and elevation)signal and elevation)

►Horizontal control ( Triangulation)and Horizontal control ( Triangulation)and Vertical control ( leveling)Vertical control ( leveling)

Procedure for Aerial survey ( Flight Procedure for Aerial survey ( Flight planning)planning)

►ParametersParameters Altitude of flight (H)Altitude of flight (H) Focal length of camera (f)Focal length of camera (f) Size of photographSize of photograph Size of area or land to be photographedSize of area or land to be photographed Alignment of flight line and parallel flight lineAlignment of flight line and parallel flight line Lateral overlapLateral overlap No of photo in each flight line and overlapNo of photo in each flight line and overlap Scale of flight map.Scale of flight map. Ground speed of aeroplaneGround speed of aeroplane Time interval of successive photographsTime interval of successive photographs

OverlapsOverlaps

OverlapsOverlaps

OverlapsOverlaps

►Longitudinal Longitudinal OverlapOverlap

►Overlap between Overlap between two photo 50% to two photo 50% to 70%70%

►Overlap between Overlap between two alternate two alternate photo 10% to photo 10% to 20%20%

►Lateral OverlapLateral Overlap►Overlap between Overlap between

adjacent flight adjacent flight lineslines

►Side overlap Side overlap should be 20% to should be 20% to 30%.30%.

Reasons for OverlapsReasons for Overlaps

►Arrangement of mosaicArrangement of mosaic►Remove errors due to distortion, Remove errors due to distortion,

displacement, and tilt.displacement, and tilt.►For view in stereoscope- 3D view.For view in stereoscope- 3D view.►Avoid repetition of aerial survey Avoid repetition of aerial survey

DD

Numbers of photographs Numbers of photographs required to cover the area Arequired to cover the area A

Number of photographs Number of photographs necessary to cover a Given necessary to cover a Given

areaarea► A = Total area to be photographedA = Total area to be photographed► l = length of photo in direction of flightl = length of photo in direction of flight►w = width of photo normal to directionw = width of photo normal to direction► s = Scale Of Photograph f/Hs = Scale Of Photograph f/H► L= net ground distance corresponding to lL= net ground distance corresponding to l►W= Net ground width corresponding to wW= Net ground width corresponding to w► a = net ground area covered by each photoa = net ground area covered by each photo► Pl = % Overlap in direction of flight(length)Pl = % Overlap in direction of flight(length)► Pw = % overlap in side (width)Pw = % overlap in side (width)

Numbers of photographs Numbers of photographs required to cover the area Arequired to cover the area A

Numbers of photographs Numbers of photographs required to cover the area Arequired to cover the area A► If actual geometry L and B known no If actual geometry L and B known no

of photographs calculated as underof photographs calculated as under

► L= Ground length of each photo ( 1-Pl)s.l. in KmL= Ground length of each photo ( 1-Pl)s.l. in Km► S= speed of aeroplane in Km/hour.S= speed of aeroplane in Km/hour.

CrabCrab

►Opposite line of photographs are not Opposite line of photographs are not parallel to flight line is known as crab parallel to flight line is known as crab of photograph.of photograph.

DriftDrift

►When aircraft is swayed away from its When aircraft is swayed away from its preplanned flight line then it is known preplanned flight line then it is known as drift.as drift.

Photomaps and MosaicsPhotomaps and Mosaics►Used as alternate of mapsUsed as alternate of maps►Photomap is single photographPhotomap is single photograph►Two or more photograph combined is Two or more photograph combined is

known as mosaic.known as mosaic.► In mosaics objects are easily recognized.In mosaics objects are easily recognized.► In maps symbols of objects are used In maps symbols of objects are used ► In mosaics true picture of objects helpsIn mosaics true picture of objects helps►Cost and time saves in mosaics preparingCost and time saves in mosaics preparing►Mosaics can be used by non technical Mosaics can be used by non technical

personperson

Procedure to prepare Photo Procedure to prepare Photo mosaicsmosaics

►Manual Manual Zerox procedureZerox procedure

►DigitalDigital Photo editing softwarePhoto editing software

STEREOSCOPESSTEREOSCOPES

Principle of stereoscopePrinciple of stereoscope

►Two separate photo viewed in Two separate photo viewed in

stereoscope the image of left stereoscope the image of left

photograph viewed by left eye and the photograph viewed by left eye and the

image of right photograph viewed by image of right photograph viewed by

right eye is fused together in brain to right eye is fused together in brain to

provide 3- dimensional view. This is provide 3- dimensional view. This is

called stereoscopic fusioncalled stereoscopic fusion

Parallax in Aerial Stereoscopic Parallax in Aerial Stereoscopic ViewView

► In normal binocular vision the apprent In normal binocular vision the apprent

movement of a point viewed first with movement of a point viewed first with

one eye and then with the other is one eye and then with the other is

known as known as Parallax.Parallax.

►Parallax is displacement of two images Parallax is displacement of two images

in successive photographs.in successive photographs.

Later……Later……

Planning and Executing Photo Planning and Executing Photo ProjectProject

► Basic Overall Process:Basic Overall Process:1.1. Photography – obtain suitable photos.Photography – obtain suitable photos.

2.2. Control – obtain sufficient control through Control – obtain sufficient control through field surveys and/or extension by field surveys and/or extension by photographic methods.photographic methods.

3.3. Map Compilation – plotting of planimetric Map Compilation – plotting of planimetric and/or topographic features.and/or topographic features.

4.4. Map Completion – map editing and special Map Completion – map editing and special field surveys.field surveys.

5.5. Final Map Drafting Final Map Drafting

Elements of PlanningElements of Planning

1.1. Conversion of requirements to Conversion of requirements to project specs.project specs.

Factors:Factors:1.1. Purpose of photogrammetryPurpose of photogrammetry

a)a) Majority of projects for engineering involves Majority of projects for engineering involves making topographic map in a stereoscopic making topographic map in a stereoscopic plotting unit.plotting unit. Wide angle photography (152mm focal length) is Wide angle photography (152mm focal length) is

required for topographic mapping because it provides required for topographic mapping because it provides better vertical accuracy.better vertical accuracy. If area is heavily wooded, use f=210mm (standard If area is heavily wooded, use f=210mm (standard

angle) to allow more visibility through trees.angle) to allow more visibility through trees. Generally 60% overlap with 15-30% sidelap.Generally 60% overlap with 15-30% sidelap. Orientation of flightlines is dictated more by economy Orientation of flightlines is dictated more by economy

than geometric considerations.than geometric considerations.

Elements of PlanningElements of Planning

b)b) Photos for mosaics should be flown as high as Photos for mosaics should be flown as high as possible.possible. Reduces relief displacement.Reduces relief displacement.

c)c) Orthophotos – similar to topo maps, however, Orthophotos – similar to topo maps, however, should be taken normal to ground topo. should be taken normal to ground topo.

2.2. Photo Scale: somewhat dependent on type Photo Scale: somewhat dependent on type of plotter.of plotter.

Essentially can be dependent on type of plotter Essentially can be dependent on type of plotter you need to see and dividing it by the resolving you need to see and dividing it by the resolving power of the photo equipment.power of the photo equipment.

Also affected by map accuracy and area Also affected by map accuracy and area configuration.configuration.

Elements of PlanningElements of Planning

3.3. Allowed scale variation.Allowed scale variation. Variation caused by difference in ground elevation Variation caused by difference in ground elevation

and flying height.and flying height. Longer focal length reduces scale variation.Longer focal length reduces scale variation. If flying height remains constant and ground If flying height remains constant and ground

elevation increases the area covered by photo elevation increases the area covered by photo becomes less.becomes less. Overlap becomes lessOverlap becomes less Viewfinder needed to control overlap and flightline Viewfinder needed to control overlap and flightline

spacing, thus eliminating possible gaps.spacing, thus eliminating possible gaps.

4.4. Relief displacementRelief displacement Affects mosaics most.Affects mosaics most.

Large amount of relief displacement will make it difficult Large amount of relief displacement will make it difficult to form continuous picture desired in mosaics.to form continuous picture desired in mosaics.

Elements of PlanningElements of Planning Relief displacement decreases as flying height Relief displacement decreases as flying height

increases, the focal length must also be increased.increases, the focal length must also be increased. Relief displacement has no adverse affect on map Relief displacement has no adverse affect on map

making with stereo.making with stereo. With greater relief displacement, elevations can be With greater relief displacement, elevations can be

measured and plotted more accurately.measured and plotted more accurately.

5.5. Tilt Tilt Amount in direction of flight (y tilt).Amount in direction of flight (y tilt).

Will cause overlap to be greater on one end than other.Will cause overlap to be greater on one end than other. Amount normal direction of flight (x tilt).Amount normal direction of flight (x tilt).

Will increase sidelap on one side and decrease on other.Will increase sidelap on one side and decrease on other. Y tilt corrected by viewfinder.Y tilt corrected by viewfinder. X tilt corrected by increasing planned sidelap.X tilt corrected by increasing planned sidelap.

Elements of PlanningElements of Planning

6.6. Crab and DriftCrab and Drift Crab – angle formed between flightline and Crab – angle formed between flightline and

edges of photo in direction of flight and caused edges of photo in direction of flight and caused by not having focal plane square with direction by not having focal plane square with direction of flight at time of exposure.of flight at time of exposure. Corrected by rotation of camera on vertical axis through Corrected by rotation of camera on vertical axis through

viewfinder.viewfinder. Reduces coverage, but sidelap compensates.Reduces coverage, but sidelap compensates.

Drift – plane not staying on flightline.Drift – plane not staying on flightline. Most common cause of re-flights and gaps.Most common cause of re-flights and gaps.

Elements of PlanningElements of Planning7.7. Flying height: determined after sidelap and Flying height: determined after sidelap and

overlap determined.overlap determined. Factors affecting:Factors affecting:

1.1. Desired scale, relief displacement, and tilt.Desired scale, relief displacement, and tilt.2.2. Precision of equipment used.Precision of equipment used.

Greater precision, greater possible flying height.Greater precision, greater possible flying height. By doubling flying height, ground coverage By doubling flying height, ground coverage

increased 4 times, thus less ground control and increased 4 times, thus less ground control and fewer photos.fewer photos.

Vertical accuracy most important in topographic Vertical accuracy most important in topographic mapping.mapping.1.1. Flying height is related to contour interval desired.Flying height is related to contour interval desired.

Relationship called C-factor (precision factor)Relationship called C-factor (precision factor) Flying height = desired contour interval x C-factorFlying height = desired contour interval x C-factor C-factor is the value used to compute flying height C-factor is the value used to compute flying height

which will produce photos satisfactory to obtain the which will produce photos satisfactory to obtain the desired vertical accuracy of the maps.desired vertical accuracy of the maps.

Elements of PlanningElements of Planning8.8. Direction or orientation of terrainDirection or orientation of terrain

Arrange to fly along ridges, not across.Arrange to fly along ridges, not across.

2.2. Gathering material and people.Gathering material and people.1.1. Existing photos, maps, survey data, Existing photos, maps, survey data,

instruments and personnel.instruments and personnel.

3.3. Determine specifications and Determine specifications and conditions for operation.conditions for operation.

4.4. Preparing final plans.Preparing final plans.1.1. Scheduling Scheduling 2.2. Surveying instructionsSurveying instructions

5.5. Cost estimating and replanning.Cost estimating and replanning.

Flight DesignFlight DesignA.A. ConsiderationsConsiderations

1.1. Project boundariesProject boundaries

2.2. Existing and planned controlExisting and planned control

3.3. Time scheduleTime schedule

4.4. Final product neededFinal product needed

5.5. Optimum flying seasonOptimum flying season

6.6. Found cover conditionsFound cover conditions

B.B. ObjectivesObjectives1.1. Determine optimum conditions for spacing of Determine optimum conditions for spacing of

photos along flightlines.photos along flightlines.

2.2. Number and spacing of fligtlines to cover area.Number and spacing of fligtlines to cover area.

3.3. Plan must account for allowable deviations.Plan must account for allowable deviations.

4.4. Distance between flightlines on fllightway. Distance between flightlines on fllightway.

Flight DesignFlight Design

C.C. Flight PatternsFlight Patterns1.1. Totally dependent on overlap and sidelap.Totally dependent on overlap and sidelap.

Under ideal conditions with 9”x 9” photo with 6” Under ideal conditions with 9”x 9” photo with 6” focal length, and overlap of 57%, and sidelap of focal length, and overlap of 57%, and sidelap of 13% will provide maximum stereo coverage with 13% will provide maximum stereo coverage with no gaps.no gaps. If additional safety factor desired, overlap can be If additional safety factor desired, overlap can be

increased to 70-75% and sidelap can be increased to increased to 70-75% and sidelap can be increased to 50%.50%.

Computation of Flight PlanComputation of Flight Plan► Data required to compute flight map lines, time Data required to compute flight map lines, time

interval between exposures, and amount of interval between exposures, and amount of film needed.film needed.

1.1. Focal length of camera.Focal length of camera.

2.2. Flying height above datum or photo scale for certain Flying height above datum or photo scale for certain elevation.elevation.

3.3. Size of photo.Size of photo.

4.4. Size of area to be photographed.Size of area to be photographed.

5.5. Positions of outer flight lines with respect to Positions of outer flight lines with respect to boundary.boundary.

6.6. Overlap.Overlap.

7.7. Sidelap.Sidelap.

8.8. Scale of flight map.Scale of flight map.

9.9. Ground speed of aircraft.Ground speed of aircraft.

ExampleExample

Area – 15 miles N-S & 8.5 miles E-WArea – 15 miles N-S & 8.5 miles E-W

Photos – 9” x 9”Photos – 9” x 9”

Save tobe 1:12000 @ 700’ above elevationSave tobe 1:12000 @ 700’ above elevation

Overlap – 60%Overlap – 60%

Sidelap – 35%Sidelap – 35%

Ground speed of plane – 150 mphGround speed of plane – 150 mph

Flight lines to be laid out N-S on a map @ a Flight lines to be laid out N-S on a map @ a scale of 1:62500scale of 1:62500

Outer flight lines coincide with E & W Outer flight lines coincide with E & W boundaryboundary

1.1. Flying Height:Flying Height:

12000’ above 700’ or 12700’ above sea 12000’ above 700’ or 12700’ above sea levellevel

2.2. Ground Distance Between Flight lines – since sidelap is 35%, Ground Distance Between Flight lines – since sidelap is 35%, photo distance between lines is 65% of 9”=5.85”photo distance between lines is 65% of 9”=5.85”

3.3. Number of flight linesNumber of flight lines

Total width = 8.5 miles x 5280 = 44880’Total width = 8.5 miles x 5280 = 44880’

flight lines (Round up)flight lines (Round up)

4.4. Adjust ground distance between flight linesAdjust ground distance between flight lines

5.5. Spacing of flight lines on flight mapSpacing of flight lines on flight map

5610’ on map @ 1:62500 scale5610’ on map @ 1:62500 scale

'5850'1/"12

12000'85.5

ingGroundSpac

HH 12000

11

9185850

44880

'561019

44880

"08.1'1

"12

62500

5610

6.6. Ground Distance Between Exposures with 60% overlap gain onGround Distance Between Exposures with 60% overlap gain on

each photo is 40%each photo is 40%

40% of 9” = 3.60” ground distance is:40% of 9” = 3.60” ground distance is:

'3600

'1/"12

1200060.3