VIIth International Scientific and Technical Conference From Imagery to Map: Digital Photogrammetric Technologies

Master class:Master class:Photogrammetric processing of Photogrammetric processing of pushbroom satellite imagespushbroom satellite images

Petr S. Titarov, Software Developer

September 17-20, 2007, Nessebar, Bulgaria

Master class layoutMaster class layout

Pushbroom imagery acquisitionPushbroom imagery acquisition Pushbroom imaging modesPushbroom imaging modes Pushbroom stereopairs acquisition methodsPushbroom stereopairs acquisition methods Pushbroom images blocksPushbroom images blocks Parameters of pushbroom imaging systemsParameters of pushbroom imaging systems

I. Basics of space pushbroom imagingI. Basics of space pushbroom imaging

Photogrammetric processing problemsPhotogrammetric processing problems Methods of pushbroom photogrammetryMethods of pushbroom photogrammetry

II. Pushbroom photogrammetryII. Pushbroom photogrammetry

Systems of resolution 1 meter and betterSystems of resolution 1 meter and better Systems of resolution about 2 metersSystems of resolution about 2 meters Systems of resolution 5 metersSystems of resolution 5 meters Systems of resolution 10-20 metersSystems of resolution 10-20 meters

III. Pushbroom imaging systems overviewIII. Pushbroom imaging systems overview

V. Satellite pushbroom imagery processing using PHOTOMODV. Satellite pushbroom imagery processing using PHOTOMOD

IV. Taking choice of remote sensing product for photogrammetryIV. Taking choice of remote sensing product for photogrammetry

PartPart II

Pushbroom imagery acquisitionPushbroom imagery acquisition

Pushbroom imaging modesPushbroom imaging modes

Pushbroom stereopairs acquisition methodsPushbroom stereopairs acquisition methods

Pushbroom images blocksPushbroom images blocks

Parameters of pushbroom imaging systemsParameters of pushbroom imaging systems

Basics of space pushbroom imagingBasics of space pushbroom imaging

Pushbroom image acquisitionPushbroom image acquisition

Line-by-line (pushbroom)

Pixel by pixel (whiskbroom)

Geometry of pushbroom imagery significantly differs from central projection one,Geometry of pushbroom imagery significantly differs from central projection one,so the classical photogrammetric methods are not applicableso the classical photogrammetric methods are not applicable..

Pushbroom imaging modesPushbroom imaging modes

Synchronous pushbroom imaging modeSynchronous pushbroom imaging mode

Sensor attitude is kept constant during the image acquisition

long strips acquisition is possible

the mode simplifies image geometry

Most of current imaging systems work in a synchronous way:

IKONOS

SPOT 1-5

IRS 1C/1D/P5/P6

FORMOSAT-2

Terra

ALOS…and others.

Pushbroom imaging modesPushbroom imaging modes

Asynchronous pushbroom imaging modeAsynchronous pushbroom imaging mode

Sensor attitude is rapidly changing during the image acquisition:

to enlarge the exposure

to make vector-scenes (not parallel to the satellite track)

Asynchronous mode is incident to high-resolution imaging systems like:

EROS A

QuickBird

Pushbroom stereopairs acquisition methods Pushbroom stereopairs acquisition methods

Cross-track stereo imagingCross-track stereo imaging

Cross-track (roll) tilting possibility is required

Two similar satellites can be used

Systems implementing this way of stereo imaging are, for example

SPOT 1-5 (сенсоры HRV, HRVIR, HRG)

IRS 1C/1D

Pushbroom stereopairs acquisition methodsPushbroom stereopairs acquisition methods

Along-track stereo imaging retargeting the sensorAlong-track stereo imaging retargeting the sensor

Short time gap between the stereopair images acquisition

High satellite agility is required

Systems implementing this way of stereo imaging are, for example:

IKONOS

EROS

Pushbroom stereopairs acquisition methodsPushbroom stereopairs acquisition methods

Along-track imaging using two sensors mounted on the same Along-track imaging using two sensors mounted on the same satellitesatellite

Short time gap between the stereopair images acquisition

Constant base-to-height ratio

Long stereo strips can be acquired

SPOT 5/HRS

Cartosat-1

ALOS

Terra/ASTER

Blocks of pushbroom imagesBlocks of pushbroom images

Base-to-height ratio (B:H) in theoverlapping areas is arbitrary.

Block of single images (“monoblock”)

New (ordered) imaging

Block composed of archive images

Blocks of pushbroom imagesBlocks of pushbroom images

Block of stereopairs (“stereoblock”)

The set of overlapping stereopairs

Pushbroom imaging systems parametersPushbroom imaging systems parameters

Geometric parameters:Geometric parameters:

Example: SPOT/HRG

Ground sample distance

Swath width

Depends on: detector size focal length orbit altitude

Depends on: focal length < the two determine detectors size and count < the field of view orbit altitude tilting

Tilting capability

Depends on: sensor and satellite design

Pushbroom imaging systems parametersPushbroom imaging systems parameters

The main radiometric parametersThe main radiometric parameters

Spectral channels

Count and the wavelength range

Radiometric resolution

Dynamic range

Imaging system productivityImaging system productivity

Depends on: swath width satellite orbit tilting capability imaging mode (synchronous/asynchronous) stereoscopic imaging method on-board storage capacity parameters and placement of receiving stations

Remote sensing satellites orbitsRemote sensing satellites orbits

02

cos51cos

2

aei

iN

iN

Major semi-axis a determines the satellite altitude

Eccentricity e0 (circular orbit) constant satellite altitude

Inclination i98 (near-polar sun-synchronous orbit) almost all the Earth is observable satellite passes nodes every revolution at the same local time

Celestial longitude of the ascending node subject to perturbation

Argument of perigee does not matter for circular orbit

Secular perturbation per N revolutions:

Geo-synchronous orbit satellite track periodically repeats

Remote sensing satellites orbitsRemote sensing satellites orbits

Polar orbit Sun-synchronous orbit

Sun-synchronous orbitSun-synchronous orbit

t1

t2

t3

The sun

Satellite orbitplaneOrbit of the

Earth

The Earth t

t

t

The sun

Satellite orbitplaneOrbit of

the Earth

The Earth

PartPart IIII

Problems solved to perform photogrammetric processingProblems solved to perform photogrammetric processing Methods of pushbroom photogrammetryMethods of pushbroom photogrammetry

Pushbroom photogrammetryPushbroom photogrammetry

),,(

),,(),,(

),,(

4

3

2

1

NNN

NNNN

NNN

NNNN

hP

hPy

hP

hPx

4,1,3

0

3

0

3

0),,(

3

qi j k

kN

jN

iNijkqhP ha

kji

NNNq

r2

r1

S1

S2

Orbit

Earth

G

S1

S2

M

ray 1ray 2

Space resection and space intersectionSpace resection and space intersection

GCPs

Single images

DEM3D vectors

Orthoimagery2D vectors

DEM

GCPs

Stereopairs

Ortho-mosaics

Export to GIS, CAD,

digital maps

right

right

left

left

y

x

y

x

f

Z

Y

X

Z

Y

X

gy

x

Methods of pushbroom photogrammetryMethods of pushbroom photogrammetry

Rigorous Replacement models

Methods of pushbroom photogrammetry

Modeling imagery acquisition geometry

Using abstract relationships that approximate rigorous

imaging model

Generic

Using a-priory relationships containing parameters determined from GCPs

),,(

),,(),,(

),,(

4

3

2

1

NNN

NNNN

NNN

NNNN

hP

hPy

hP

hPx

4,1,3

0

3

0

3

0),,(

3

qi j k

kN

jN

iNijkqhP ha

kji

NNNq

1

1

321

4321

321

4321

ZCYCXC

BZBYBXBy

ZCYCXC

AZAYAXAx

r2

r1

S1

S2

Orbit

Earth

G

S1

S2

M

ray 1ray 2

Rigorous methodRigorous method

Ray’s edges: )(lSS

Ray’s directional vectors: ),( plrr

l – line number p – detector number

Sensor motion model: )(lSS

Ray’s directional vector: )()(),( plPplr

Attitude model: )(lPP

Sensor geometry model: )( p

Reconstruction of:

Models used:

Ray’s edge: )(lSS

Reconstructed vectors:

Sensor geometrySensor geometry ( (interior orientationinterior orientation))

Tabulated vector-function2D central projection

)( p

1

p )( p

p1

p2

1

2

The model defines the directional vector of ray sensed by the detector number p with respect to the sensor reference system S:

The model is the analog of interior orientation elements in classical photogrammetry.

Sensor motion modelSensor motion model

Polynomial modelPolynomial model Orbital modelOrbital model

Z

Y

X

n

k

kk

n

j

jj

n

i

ii

lCZ

lBY

lAX

0

0

0

Keplerian orbit parameters:• major semi-axis a • eccentricity e• inclination i• celestial longitude of the ascending node • argument of perigee • perigee passing time

Parameters to be refined:

e, i, ,, sometimes a

Parameters to be refined:

Ai , Bj , Ck

applicable in any Cartesian reference system (including ECR) simple to implement

inertial reference system must be used physical model only a few parameters to refine

Sensor attitude modelSensor attitude model

The model is defined by the three angles , , , which polynomially depend on the line number l, or it can be represented as the sum of the measured in-flight values and polynomial refinements:

K

k

kkèçì

J

j

jjèçì

I

i

iièçì

lll

lll

lll

0

0

0

)()(

)()(

)()(

The model defines the rotation of the sensorreference system with respect to the geocentricReference system.

))(),(),(()( lllPlP

Rigorous solution of space resection and space Rigorous solution of space resection and space intersection intersection

Space intersectionSpace intersection Space resectionSpace resection

Z

Y

X

fy

x

2

2

1

1

y

x

y

x

g

Z

Y

X

Correspondent rays intersection Iterative process

Imagery orientationImagery orientation

0)( SMrSMr

Z

Y

X

SM

Z

Y

X

Pr

,

0

0

0

XYYX

ZXXZ

YZZY

Any two of the three equations are independent:

The image orientation is based on the collinearity condition:

GenericGeneric ( (parametricparametric) ) methodmethod

Using some a-priory equations derived from coarse assumptions concerning imaging geometry whichrelate image coordinates x, y to ground ones X,Y,Z.The values of the parameters involved into the equations are calculated using GCPs.

),...,,,,(

),...,,,,(

1

1

m

n

qqZYXgy

ppZYXfx

Direct Linear Transformation (DLT)

1

1

321

4321

321

4321

ZCYCXC

BZBYBXBy

ZCYCXC

AZAYAXAx

Parallel-perspective model

1

1

321

321

4321

ZCYCXCy

ZBYBXB

AZAYAXAx

Replacement models

They are models which approximateground-to-image correspondencecalculated using rigorous method:

),,(

),,(

ZYXGy

ZYXFx

or, more often,

),,(

),,(

ZyxGY

ZyxFX

RPC = Rational Polynomial Coefficients = Rapid Positioning Capability

),,(

),,(),,(

),,(

4

3

2

1

NNN

NNNN

NNN

NNNN

hP

hPy

hP

hPx

4,1,

3

0

3

0

3

0),,(

3

qi j k

kN

jN

iNijkqhP ha

kji

NNNq

Basic relationships:

, where

N, N, hN - normalized ground coordinates:

(-1 N 1, -1 N 1, -1 hN 1)

h

hNNN s

ohh

s

o

s

o

xN, yN - normalized image coordinates:

(-1 xN 1, -1 yN 1)

y

yN

x

xN s

oyy

s

oxx

Adjustment-derived refinements:

DsDlD

DyDxD

ybxbbyy

yaxaaxx

0

0

0

0

byy

axx

D

D

или

Algebraic solution of space intersection and space resection

Space intersectionSpace intersection Space resectionSpace resection

Z

Y

X

fy

x

2

2

1

1

y

x

y

x

g

Z

Y

X

),,(),,( ZYXGyZYXFx iiii

Based on relationships:

Directly by formula

),,(

),,(

ZYXGy

ZYXFx

ii

ii

Least-squares estimation of 3 unknowns X, Y, Z from 4 non-linear equations:

0),,(

0),,(

0),,(

0),,(

22

22

11

11

ZYXGy

ZYXFx

ZYXGy

ZYXFx

PartPart IIIIII

Systems of resolution of Systems of resolution of 1 1 m or betterm or better

Systems of resolution aboutSystems of resolution about 2 2 mm

Systems of resolution Systems of resolution 5 5 mm

Systems of resolution Systems of resolution 10-20 10-20 mm

Pushbroom imaging systems overviewPushbroom imaging systems overview

Systems of resolution 1 m or betterSystems of resolution 1 m or better

Systems of resolution 1 m or betterSystems of resolution 1 m or better

Systems of resolutionSystems of resolution about about 2 2 mm

Systems of resolutionSystems of resolution 5 5 mm

Systems of resolutionSystems of resolution 10-20 10-20 mm

PartPart IVIV

Taking choice of remote sensing product for photogrammetryTaking choice of remote sensing product for photogrammetry

One should take into consideration the following aspects:

if the imagery is geometrically pre-processed

metadata contents (if it contains the image geometry)

possibility to order polygones or sub-scenes

data format

Geometric preprocessingGeometric preprocessing

Rigorous methods are not applicable to the geometrically preprocessed imagery!

Example:

Imaging systemImaging system

Geometrically rawGeometrically raw Geometrically correctedGeometrically corrected

Remote sensing productRemote sensing product

SPOT, ASTERSPOT, ASTER 1A1A 1B1B

KOMPSAT, LandsatKOMPSAT, Landsat 1R1R 1G1G

QuickBirdQuickBird BasicBasic StandardStandard

OrbView-3OrbView-3 BASICBASIC GEOGEO

Metadata contents and data file formatMetadata contents and data file format

Cartosat-1 stereopairCartosat-1 stereopair

Stereo Ortho KitStereo Ortho Kit Basic stereoBasic stereo

TIFF raster andTIFF raster and RPCRPC Super Structured file format, Super Structured file format, processing using generic methodsprocessing using generic methods

PartPart VV

Satellite pushbroom imagery processing using PHOTOMODSatellite pushbroom imagery processing using PHOTOMOD

PHOTOMOD supported sensorsPHOTOMOD supported sensors

Remote sensing product files set structureRemote sensing product files set structure

QuickBird Basic product files set

Connection between IKONOS Geo Ortho Kit product

imagery and RPC files

<image file name>.tif<image file name>.tif

<image file name>_rpc.txt<image file name>_rpc.txt

QuickBird Standard Tiled StructureQuickBird Standard Tiled Structure

QuickBird Standard and Standard Ortho Ready imagery can be tiled.

RPC refers to the composed image!

Collective processing of imagery acquired by different Collective processing of imagery acquired by different sensorssensors

Possible candidates for collective processingPossible candidates for collective processing::

SPOT-5 Supermode (2.5 m)SPOT-5 Supermode (2.5 m) FORMOSAT 2 PAN (2 FORMOSAT 2 PAN (2 m)m)

IKONOS + OrbView-3 + Kompsat-2IKONOS + OrbView-3 + Kompsat-2

++

Thank you for your attentionThank you for your attention!!