1. September 17-20, 2007, Nessebar, Bulgaria
VIIth International Scientific and Technical Conference From Imagery to Map:
Digital Photogrammetric Technologies
Master class:
Photogrammetric processing of pushbroom satellite images
Petr S. Titarov, Software Developer
September 17-20, 2007, Nessebar, Bulgaria

2. Master class layout I. Basics of space pushbroom imaging
Pushbroom imagery acquisition
Pushbroom imaging modes
Pushbroom stereopairs acquisition methods
Pushbroom images blocks
Parameters of pushbroom imaging systems
II. Pushbroom photogrammetry
Photogrammetric processing problems
Methods of pushbroom photogrammetry
III. Pushbroom imaging systems overview
Systems of resolution 1 meter and better
Systems of resolution about 2 meters
Systems of resolution 5 meters
Systems of resolution meters
IV. Taking choice of remote sensing product for photogrammetry
V. Satellite pushbroom imagery processing using PHOTOMOD

3. Part I Basics of space pushbroom imaging Pushbroom imagery acquisition
Pushbroom imaging modes
Pushbroom stereopairs acquisition methods
Pushbroom images blocks
Parameters of pushbroom imaging systems

4. Pushbroom image acquisition
Line-by-line
(pushbroom)
Pixel by pixel
(whiskbroom)
Geometry of pushbroom imagery significantly differs from central projection one, so the classical photogrammetric methods are not applicable.

5. Pushbroom imaging modes
Synchronous 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.

6. Pushbroom imaging modes
Asynchronous 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

7. Pushbroom stereopairs acquisition methods
Cross-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

8. Pushbroom stereopairs acquisition methods
Along-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

9. Pushbroom stereopairs acquisition methods
Along-track imaging using two sensors mounted on the same satellite
SPOT 5/HRS
Cartosat-1
ALOS
Terra/ASTER
Short time gap between the stereopair images acquisition
Constant base-to-height ratio
Long stereo strips can be acquired

10. Blocks of pushbroom images
Block of single images (“monoblock”)
New (ordered) imaging
Base-to-height ratio (B:H) in the
overlapping areas is arbitrary.
Block composed of archive images

11. Blocks of pushbroom images
Block of stereopairs (“stereoblock”)
The set of overlapping stereopairs

12. Pushbroom imaging systems parameters
Geometric parameters:
Ground sample distance
Depends on:
detector size
focal length
orbit altitude
Tilting capability
Depends on:
sensor and satellite design
Swath width
Depends on:
focal length < the two determine
detectors size and count < the field of view
orbit altitude
tilting
Example: SPOT/HRG

13. Pushbroom imaging systems parameters
The main radiometric parameters
Spectral channels
Count and the wavelength range
Radiometric resolution
Dynamic range
Imaging 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

14. Remote sensing satellites orbits
Major semi-axis a
determines the satellite altitude
Eccentricity e0 (circular orbit)
constant satellite altitude
Inclination i98 (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

15. Remote sensing satellites orbits
Sun-synchronous orbit
Polar orbit
Sun-synchronous orbit

16. Pushbroom photogrammetry
Part II
Pushbroom photogrammetry
Problems solved to perform photogrammetric processing
Methods of pushbroom photogrammetry

17. Space resection and space intersection
Single images
Orthoimagery
2D vectors
Ortho-
mosaics
Export to
GIS, CAD,
digital maps
GCPs
DEM
Stereopairs
DEM
3D vectors
GCPs

18. Methods of pushbroom photogrammetry
Rigorous
Generic
Replacement models
Modeling imagery
acquisition geometry
Using a-priory relationships
containing parameters
determined from GCPs
Using abstract relationships
that approximate rigorous
imaging model

19. Rigorous method l – line number Reconstruction of: Ray’s edges:
Ray’s directional vectors:
l – line number
p – detector number
Models used:
Sensor motion model:
Sensor geometry model:
Attitude model:
Reconstructed vectors:
Ray’s edge:
Ray’s directional vector:

20. Sensor geometry (interior orientation)
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.
2D central projection
Tabulated vector-function p p1 p2 

21. Parameters to be refined:
Sensor motion model
Polynomial model
Orbital model
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

22. Sensor attitude model The model defines the rotation of the sensor
reference system with respect to the geocentric
Reference system.
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:

23. Rigorous solution of space resection and space intersection
Iterative process
Correspondent rays intersection

24. The image orientation is based on the collinearity condition:
Imagery orientation
The image orientation is based on
the collinearity condition:
Any two of the three equations are independent:

25. Generic (parametric) method
Using some a-priory equations derived from coarse
assumptions concerning imaging geometry which
relate image coordinates x, y to ground ones X,Y,Z.
The values of the parameters involved into the equations
are calculated using GCPs.
Parallel-perspective model
Direct Linear Transformation (DLT)

26. Replacement models They are models which approximate
ground-to-image correspondence
calculated using rigorous method:
or, more often,

27. RPC = Rational Polynomial Coefficients = Rapid Positioning Capability
Basic relationships:
, where
N, N, hN - normalized ground coordinates:
(-1 N 1, -1 N 1, -1 hN 1)
xN, yN - normalized image coordinates:
(-1 xN 1, -1 yN 1)
Adjustment-derived refinements:
или

28. Algebraic solution of space intersection and space resection
Based on relationships:
Space intersection
Space resection
Least-squares estimation of 3 unknowns
X, Y, Z from 4 non-linear equations:
Directly by formula

29. Pushbroom imaging systems overview
Part III
Pushbroom imaging systems overview
Systems of resolution of 1 m or better
Systems of resolution about 2 m
Systems of resolution 5 m
Systems of resolution m

30. Systems of resolution 1 m or better

31. Systems of resolution 1 m or better

32. Systems of resolution about 2 m

33. Systems of resolution 5 m

34. Systems of resolution 10-20 m

35. Taking choice of remote sensing product for photogrammetry
Part IV
Taking 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

36. Geometric preprocessing
Rigorous methods are not applicable to
the geometrically preprocessed imagery!
Example:
Imaging system
Remote sensing product
Geometrically raw
Geometrically corrected
SPOT, ASTER 1A 1B
KOMPSAT, Landsat 1R 1G
QuickBird
Basic
Standard
OrbView-3
BASIC
GEO

37. Metadata contents and data file format
Cartosat-1 stereopair
Stereo Ortho Kit
Basic stereo
TIFF raster and RPC
Super Structured file format,
processing using generic methods

38. Satellite pushbroom imagery processing using PHOTOMOD
Part V
Satellite pushbroom imagery processing using PHOTOMOD

39. PHOTOMOD supported sensors

40. Remote 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>_rpc.txt

41. QuickBird Standard Tiled Structure
QuickBird Standard and Standard Ortho Ready imagery can be tiled.
RPC refers to the composed image!

42. Collective processing of imagery acquired by different sensors
Possible candidates for collective processing:
SPOT-5 Supermode (2.5 m) +
FORMOSAT 2 PAN (2 m)
IKONOS OrbView Kompsat-2

43. Thank you for your attention!